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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 01, , HOMEOSTASIS, DEFINITION AND SIGNIFICANCE:, “The maintenance of the dynamic equilibrium to achieve a constant or nearly constant state of, internal environment”, is called as homeostasis., It applies to body temperature, Body water, pH, ions, blood pressure etc. An organism is a complex, system of chemical process., The advantage of a constant internal environment was first pointed out by the French Physiologist, Claude Bernard (1857). Where as in 1932 the American physiologist Walter Cannon introduced, the term ‘Homeostasis’ (homeo - same stasis - standing) constancy of the internal environment is, maintained & is essential for an independent life., WATER BALANCE:, Removal of Excess Water:, In case of freshwater animals, the body fluid is hypertonic and the fresh water is hypotonic, hence, endosmosis occurs., Therefore, the fresh water animals have the following adaptations to deal with the excess of water, entering the body., a. Amoeba removes the excess of water by contractile vacuoles (*Chief Osmoregulatory, organelle)., b. Crustacean removes the excess of water by green glands*., c. Fresh water fishes remove the excess of water by the glomerular kidney., , 1, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Compensation of water Loss:, In case of marine animals, the body fluid is hypotonic and the sea water is hypertonic. Hence,, exosmosis occurs in marine animals. As a result, the marine animals are dehydrated; the loss of, water is compensated by drinking sea water and by getting water from marine food., The land animals are dehydrated by evaporation; they compensate the water loss by drinking, water and by getting water from food & metabolism., GLUCOSE BALANCE:, Carbohydrates are the cheapest source of energy in the animal food when carbohydrates undergone, hydrolysis results in Glucose. The concentration of glucose in the blood is remarkably constant in, spite of the various factors operating to upset it., In normal healthy individual blood glucose ranges from 80 to 120mg/100ml., In fasting stage 75 to 100mg/100ml and soon after the meal the glucose level increase to 100140mg/100mg but within 2 to 3 hrs. the normal level is reached., The rise in the blood glucose/sugar above the normal level is called hyperglycaemia and the fall, in the blood sugar, below the normal level is called hypoglycaemia., REGULATION OF BLOOD GLUCOSE:, Soon after the meal when the blood glucose level raises the rate of insulin hormone is secreted by, the β-cells of pancreas to convert the excess of glucose into glycogen and stored in liver and, muscle. After few hours when glucose concentration decreases the insulin secretions also decrease., The process of conversion of excess glucose into glycogen is known as Glycogenesis., , 2, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, Excess of the, Glucose, eliminated in the, Urine, , Kidney, , Pancrease, β-cells of Islets of, Langerhans, secretes, Insulin Hormone, , Glucosuria, , Excess Glucose, as Waste, , Glycogen stored in, Liver, and, Muscle, Cells, , Glycogenesis, (Conversion of excess, Glucose into Glycogen), , Rise in, Blood Glucose, Above 120, mg/100ml, , Decreasing, Blood Glucose, to the normal range, , Normal, Blood Glucose, 80-120 mg/100ml, Decreasing, Blood Glucose, Below 80 mg/100ml, , Rise in, Blood Glucose, to the normal range, , Pancrease, α-cells of Islets of, Langerhans, secretes, Glucagon Hormone, , Glycogenolysis, , Glucose released, into Blood, , (Breakdown of, Glycogen into Glucose), , Kidney, , Excess of the, Glucose, will be reabsorbed, from the Urine, , Adrenal Gland, , Secretes, Adrenalin, Hormone, , Gluconeogenesis, (Production of Glucose, from, Non-Carbohydrate sources), , BLOOD GLUCOSE HOMEOSTASIS, , When the blood glucose falls below the normal the α-cells of the pancreas secrete glucagon, hormone and in liver it induces liver to release the glucose back into the blood., The process of conversion of stored glycogen into glucose is known as Glycogenolysis., When the amount of stored up glycogen in the muscle and liver gets reduced the amino acids enter, the process of Gluconeogenesis in the liver which results in the production of glucose, so liver has, an important role in the finely regulated homeostatic mechanism., Kidneys also have regulating the blood glucose level in the body. Renal tubules have power of, reabsorption of glucose filtered by Glomerulus & the urine which is excreted in a normal healthy, person is almost free from glucose., 3, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , If it exceeds the range of reabsorption the excess of glucose is excreted in urine& the condition is, known as Glucosuria., During the emergency (i.e., at the time of shock or stress) Adrenal Gland secretes Adrenalin Hormone, which is responsible for the process of conversion of non-carbohydrates (such as lactate, amino, acids and glycerol) into glucose (carbohydrate) is known as Gluconeogenesis., SALT BALANCE:, Removal of excess of salts:, When marine animals drink sea water to compensate their water loss, the salt content of the body, increases. The excess of salt is removed from the body by any one of the following methods., a. The marine fishes have chloride secretary cells in their gills they secrete excess of salts, present in the body fluid., b. In case of marine turtles and marine birds salt gland (present in the head) secrete out the, excess of salt., Compensation of salt loss:, When fresh water animals expect the excess of water some amount of salt from the body is also lost,, this loss of salt is made good by the following methods., a., , Crustaceans & fresh water fishes have special kind of cells in the gills they are called, Chloride cell. They absorb salt from the fresh water and add to the body fluid., , b., , The kidney of freshwater fishes reabsorbs some salts from the urine., , “All powers are within YOU, you can do anything and everything”., Swami Vivekananda, , ******, 4, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, ds, , CHAPTER – 02, , OSMOREGULATION, , OSMOCONFORMERS:, Some animals are osmotically dependent and the concentration of their body fluids changes, according to the medium in which they live such animals are called as osmoconformers., (or) Animals that maintain their body fluid concentration more or less similar to that of the, environment are called Osmoconformers., Osmoconformers are further classified into 2 types on the basis of their tolerance to salinity, STENOHALINE:, The organisms which can-not tolerate changes in salinity are called stenohaline organisms., Animals which are restricted to narrow range of salinity, they can live only in full sea water., e.g., Maia is marine Crab, is a stenohaline animal because it, can-not tolerates even slight changes in salinity., When marine crab is transferred to 75% sea water (sea water, diluted with 25 parts of distilled water) the Crab, dies in 18Hrs., Because, the 75% sea water become hypotonic and the body, fluid become hypertonic. Hence endosmosis occurs., , Maia – Marine Crab, , As a result of endosmosis water enters the body and there is an increase in the water content of, the body (crab). The excess of water is removed in the form of urine; along with urine large, amount of salt is lost; As the Crab is not able to make good this salt loss, so it dies., , 5, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , EURYHALINE:, The organisms which can tolerate wide change in salinity are, called euryhaline organisms. Hence exosmosis occurs when these, organisms are exposed to low dilutions of sea water they can, adjust the salinity of their body fluid to exactly the same, concentration of the external medium., e.g., Phascalosoma lives unaffected for several days in 50%, Phascalosoma – Sea Worm, sea water. In 50% diluted sea water its body weight increases by, 23% owing to endosmosis. In 60% sea water, its body weight decreases owing to exosmosis., OSMOREGULATORS:, The animals which maintain a constant internal body fluid concentration are called, osmoregulators. (or) The animals that maintain their body fluid concentration more or less constant, irrespective of fluctuations in the environmental concentration are called Osmoregulators., e.g., Amoeba, Crustaceans, (Cray fish, brine shrimp, Estuarine Crab), Fishes, Amphibia, Reptiles,, Birds & Mammals., Osmoregulation in Amoeba:, Amoeba, , is, , a, , fresh, , water, , organism, the fresh water is, hypotonic and the body fluid is, hypertonic,, , hence, , endosmosis, , occurs. The excess of water is, removed by contractile vacuole., , 6, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , OSMOREGULATION IN FRESH WATER TELEOSTS (BONY FISHES):, , Salt along with, Food and Water, , 1. The body fluid of fresh water teleost fish is hypertonic the fresh water is hypotonic., 2. Hence endosmosis occurs as unavoidable condition. As a result, fresh water enters into the, body fluid and the volumes of body fluid increase to 30% of its body weight daily., 3. Excess of water fluid is removed from the body in the form of urine by glomerular kidney., 4. Along with the urine some amount of salt is also lost. Hence the salt content of the body, fluid decreases., 5. This salt loss is compensated by the absorption of salts from the fresh water by the chloride, cells of the gills and kidneys actively reabsorbs salt from the glomerular filtrate in addition, to renal absorption of salts some solutes are taken through food., OSMOREGULATION IN MARINE TELEOSTS:, , 7, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 1. The body fluid of marine teleost is hypotonic and the sea water is hypertonic. Hence,, exosmosis occurs., 2. So problem in osmoregulation of these marine teleost is avoiding loss of water and gaining, of salts., 3. Unlike fresh water teleost, marine teleost also drinks large quantity of water in sea (50200ml/Kg body weight)., 4. 60-80% of salt from food absorbed through the intestine along with Na+&K+ (Monovalent, ions) and small quantities of Ca++ and Mg++ (Divalent ions)., 5. The salt gained by marine teleost must be excreted in higher concentration than the water, takes in., 6. In teleost the gills and kidney serve this purpose through active transport., 7. With the help of chloride secretary cells of gills, the monovalent ions are secreted out., 8. Divalent ions are excreted along with urine with the help of kidney (glomerular kidney). A, glomerular kidney reabsorbs water from the urine and hence prevents the loss of water, Urine. As a result, the urine become concentrated., 9. By intake of large volume of water, it can overcome from the problem of Osmotic, dehydration., 10. The dehydration occurring in marine fishes is called physiological dehydration; it makes the, fish dry in sea water., OSMOREGULATION IN SHARK:, , 8, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 1. Marine animals are usually osmoregulators but the Shark [Elasmobranches] is exception, they adapted for the marine life with Osmoconfirmation., 2. Sharks have an osmotic pressure similar to that of sea water, this condition is called, isotonic., 3. This is achieved through retaining large amount of organic compounds like urea and, Trimethylamine N-Oxide [TMAO]., 4. This high concentration of urea and TMAO could not be tolerated by other vertebrates., 5. Sharks maintain Na+ concentration in this blood half of that of sea water. Sodium gain, through food and gill surface is compensated by excretion through kidneys and rectal, glands., 6. The blood urea concentration in elasmobranches is more than 100 times higher than, mammals., 7. In elasmobranches urea is a normal component of all body fluid and tissue cannot function, normally in the absence of a high urea concentration., 8. In shark chloride secretary cells are absent whereas kidney reabsorbs urea from the urine., 9. The urea is retained in the body fluid and hence the body fluid becomes isotonic to sea, water. This prevents osmotic dehydration., OSMOREGULATION IN TERRESTRIAL MAMMALS, Bird and Mammals use water to keep cool it body in hot surroundings, humans and some other, mammals sweat, dogs and many other mammals & birds try to keep themselves cool i.e., water is, used in thermoregulation also., OSMOREGULATION IN KANGAROO RATS:, 1. Kangaroo rats are desert rodent, abundant in North American Desert., 2. They can live without drinking free water indefinitely and depending on most food like, succulents or moist plant material., , 9, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 3. The blood of Kangaroo rat has 66% of water. The need of water for Osmoregulation and, thermoregulation met mainly through dry food/moist food and this is further metabolized, to produce metabolic water., 4. The water loss in kangaroo rats include; elimination of excretory waste through urine and, water loss along the faces., 5. The most important mean of water loss is evaporation occurring through mouth from the, respiratory tract., 6. Although water is conserved by excreting concentrated urine (less amount of water in urine), and a very little water loss in the faeces, loss of water through the respiratory surface is, inevitable., 7. The kangaroo rats dig burrows and live inside during daytime to protect themselves from, predator & heat., 8. Kangaroo rats are nocturnal (active during night) to avoid the heat during day time., 9. Sweat glands are absent in Kangaroo Rat, this helps in conserving of water., 10. The kidney tubules reabsorb more of water and thus excrete concentric urine, this is also, mean of water conservation., 11. Kangaroo rats obtain their water from the food they eat as well as the metabolic water., 12. Therefore, osmoregulation in Kangaroo rat is as much behavioural as physiological., , 10, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Succulent Plant, Food, Gain of Water, Metabolic Water, , Physiological, Conservation of, Water, , Behavioural, Conservation of, Water, , Water, Reabsorption in, Intestine, Water, Reabsorption in, Kidney Tubules, , Urine, , Water in the, Body Fluid, , Loss of Water, , (Blood, &, Cell Cytoplasm), , Feaces, , Evoporation, , Remain in, Burrows during, day time, , Nocturnal mode, of life, , OSMOREGULATION IN CAMEL:, 1. Camel is a desert mammal, called the ‘ship of the desert’ as it is well adapted to live in hot, sand of deserts., 2. Camel is a eurythermal animal as it has the ability to tolerate wide variations in, temperature., 3. Camel is a warm blooded animal as it can keep its body temperature well above the ambient, temperature as other mammals and birds., 4. Camel has thick skin that helps insulate from external heat., 5. Camel is a temporal heterothermic animal as their body temperature is very high during, hot day and very low during cool night., 6. It cannot maintain the body temperature within a narrow range. It absorbs heat and allows, its body temperature to go high up to 58C on a hot day. Similarly during night, it allows its, body temperature to drop several degrees below normal (34C) body temperature., 7. Camels sweat only when the body temperature rises alone to 41-58C so it avoids loss of too, much water from body., 11, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 8. Camel can go a week or more without drinking water, and they can last for several months, without food., 9. They can drink up to 46 litres of water at one drinking session and can drink up to 1/3 of, the body weight in 10min., 10. Camels store fat in the hump, not water and the fat can be metabolized for energy and, water., 11. It excretes concentrated urine (more salt & less water in urine) the Henle’s loop of nephron, helps to adjust the concentration urine., 12. Reabsorption of water from urine and faces and utilize the metabolic water (fat, metabolism)., 13. Camel produce concentrated milk to conserve water., , 12, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Succulent Plant, Food, Gain of Water, Metabolic Water, , Physiological, Conservation of, Water, , Water, Reabsorption in, Intestine, Water, Reabsorption in, Kidney Tubules, , Thick Skin as, Insulator, Anatomical, Adaptations, , Fat in Hump for, Energy and, Water, , Heterothermic, , Urine, , Water in the, Body Fluid, (Blood, &, Cell Cytoplasm), , Feaces, Loss of Water, Sweat, , Behavioural, Conservation of, Water, Eurythermal, , Milk, , Sweats only, at, about 58°C, , Other, Adaptations, , Remain without, drinking water, weeks to months, Can Drink 46 L of, Water per, Drinking Session, Can Drink 1/3 of, Body Weight in, 10 Min., , “Take up one idea. Make that one idea your life - think of it, dream of it, live on that idea. Let, the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every, other idea alone. This is the way to success”., Swami Vivekananda, , 13, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 03, , THERMOREGULATION, , Q10 EFFECT (VANT HOFF’S LAW / LAW OF Q10):, In animals, physiological processes are highly temperature sensitive and are confined to very acute, temperature measurements the overall range of temperatures within which all the life processes fall, is also very narrow. Whether the environmental temperature rising or falling, manipulates the rate of, metabolic processes according., This fact has been studied by Van’t Hoff, “For every ten-degree rise in temperature the rate of, biochemical reactions becomes almost double” is known as Q10 law., , The Q 10 law can be expressed as Q10 , , K2, 10, , K1  t 2  t1 , , Where t1 = Initial temperature, t2 = final temperature, K1 = Rate of activity at t1C, K2= Rate of activity at t2C, Q10 has no theoretical basis but instead is an entirely empirical value moreover for a given reaction, the Q10 differs over different temperature ranges., The graph represents the law of Q10 (Van’t Hoff’s law). Here Oxygen consumption of an ectothermic, moth caterpillar at different temperatures. As the temperature increases to 10C the O2, consumption (metabolic rate) also increased., 14, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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OXYGEN CONSUMPTION BY, THE MOTH CATTERPILLER, (mm3/g/h), , ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 10, 8, 6, , 4, , 2, , 10, , 20, , 30, , 40, , 50, , AMBIENT TEMPERATUTE (0C), , CAUSES OF THERMAL DEATHS:, Thermal death is the death of a population of microorganisms due to exposure to an elevated, temperature. The nature of the thermal death varies depending on the source of the heat., a. The coagulation of proteins by heat is a drastic alteration in the three-dimensional shape, of these protein molecules. Thus, the alteration is irreversible and renders a protein incapable, of proper function., b. Thermal death also involves the destruction of the membranes surrounding the cell. The, high temperatures can cause the phospholipid constituents of the membrane to dissolve, and thus destroy the membrane structure., c. Finally, the high heat will also cause the destruction of the nucleic acid of the cell. In this, case, the heat will result in the dissociation of the double stranded DNA., , 15, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , THERMOREGULATION:, “Thermoregulation is a process by which the body temperature of organisms is regulated for, the effective functioning of the body”, A. Based on thermoregulation animals are of two types; Poikilothermic animals and, Homoeothermic animals, , 1. Poikilothermic animals (Thermo conformers):, In many animals the body temperature changes according to the fluctuation of, environmental temperature, these animals are called poikilothermic animals., When the environment is cold, their blood also becomes cold; hence they are also called, cold- blooded animals., They can-not regulate their body temperature by metabolism but they gain temperature from, the environment. Hence they also called ectothermic animals., E.g., All animals except birds and mammals., , 2. Homoeothermic animals (Thermo Regulators):, In some animals the body temperature remains constant and it is independent of, environmental temperature, these animals are called homoeothermic animals., When the environment is cold the blood of these animals will be at a higher temperature,, hence these animals are also called Warm blooded animals., They can regulate their body temperature by generating heat through metabolic activities,, hence they are also called Endothermic animals., E.g., Birds and mammals, 16, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , B. Based on the sources of body heat animals are classified into three types: Ectotherms,, Endotherms and Heterotherms, 1. Ectotherms:, Ectotherms are animals depending on their surrounding for the source of body heat., E.g., All animals except birds & mammals, Invertebrates like - fishes, amphibians, Reptiles, etc. characteristics of Ectotherms., In ectotherms the body temperature passively adjusted with the surrounding (ambient), temperature., They have low rates of metabolic heat production., They have high thermal conductance and are poorly insulated. As a result, the heat derived, from metabolic process is quickly lost to the surroundings., They regulate their body temperature by behavioural temperature regulation., , 2. Endotherms:, Endotherms are animals which “generate heat on their own body”., E.g., Birds and mammals, The endotherms maintain their body temperature well above the ambient (surrounding), temperature in cold climates., They have high rates of metabolic heat production., The metabolic rate of an endotherm at rest is at least 5 times that of an ectotherm of equal, size., They are well insulated with feathers & fur., They regulate their body temperature by thermogenesis (generating of the temperature, within body)., 17, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 3. Heterotherms, Heterotherms behave like ectotherms and endotherms. Like endotherms they can generate, body heat, & like ectotherms they cannot maintain (regulate) the body temperature within, a narrow range., E.g., Python, Echidna, Camel, many flying insects, etc., Heterotherms are again of two types; Temporal heterotherms and Regional heterotherms, a. Temporal heterotherms:, The animals maintain varying body temperature at different times is called temporal, heterotherms., E.g., Pythons, flying insects, etc., Temporal heterotherms raise their body temperature well above the ambient temperature, by muscular activity., Some insects prepare for flight by exercising their flight muscles for a time to raise their, temperature before take-off., Some insects such as honeybees, regulated the temperature by group behaviour. In a very, cold environment the clusters of bees (Swarm) work together to keep the queen warm. The, shivering movement of their contractile muscles changes the structure of swarm. So as cold, temperature the bees come closed in a way they clustered tightly so to prevent the free, movement of air., On a hot day the camel absorbs heat and allows its body temperature to go high up. At, night, it allows its body temperature to drop several degrees below normal so the camel, is temporal heterotherms., 18, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , b. Regional Heterotherms:, Some poikilotherms maintain different temperature in different regions of the body., These animals are called regional heterotherms., e.g., Mako shark, Bluefin Tuna, many flying insects, Penguins, etc., In Mako Shark and Bluefin Tuna maintains high temperature in the core (deeper part of the, body) & low temperature in the periphery., Insects before the flight, warm up of the muscles by, simultaneously contract and pull, against one another resulting in heat production. Around 40ºC temperature of thoracic, muscles then the flight is initiated., Seals and penguins swimming in cold water also have been found to maintain high, temperatures in major locomotor muscles (like limbs or foot)., , 19, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , HIBERNATION:, Hibernation is a phenomenon where the animals undergo dormancy to escape from excessive cold., It takes place in winter; hence it is also called winter sleep., It is exhibited mainly by Homeotherms like Rodents, Insectivores, chiropteran (Bat) Humming, bird etc. and mainly in poikilotherms like frog, Toad and Reptiles., In cold climatic conditions the food is scare and also the food requirement to conduct normal, metabolism becomes very high. Both these lead to many deaths because of starvation. To prevent, death from such situation many animals pass their winter in lethargic (inactive) states by Hibernation., It is characterized by the following character;, 1. Animals find themselves in crevices, under-rocks, burrows and muds., 2. Toads and frogs hibernate in solitary burrows on land., 3. Reptiles aggregate in large numbers below rocks or in burrows., 4. Aquatic turtles burry themselves in mud under ponds., 5. The hibernating animals do not feed & they starve, because of low body temperatures the, heat losses get minimized and thus only a small amount of food is required by the animal., 6. They do not move and therefore body temperature is reduced., 7. Body reserve such as fats and glycogen are used for the energy requirements., 8. Respiratory rate is reduced and rate of heart beat is reduced., 9. Arousal from hibernation is explosive and it occurs when the climate becomes suitable. All, physiological activates come to normal during arousal., 10. They do not show growth and reproduction during hibernation., , 20, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , AESTIVATION:, Aestivation is a state of dormancy (lying inactive /sleeping) occurring in summer to escape from, the scorching heat of Sun. As it occurs in summer, it is also called summer sleep., It is exhibited by lady bird beetles, lung fishes, snails, snakes, lizard, tortoises, Australian frog,, Rodents, insectivores, ground squirrels, etc., 1. The snail seeks cool shady places during summer, secretes, a thin membrane called epiphragm to close the shellmouth and remains dormant., 2. The lung fish (Protopterus) burrows into the mud secretes, a cocoon of slime around itself and remains dormant, throughout summer. The burrow is in the form of a tube, & it opens to the outside., , 21, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 3. Many small animals like Amoeba, molluscs also found enter a state of protection by cocoons., 4. During adverse environmental conditions many Amoebas survive by Encystment: The, Amoeba becomes circular, loses most of its water, and secretes a cyst membrane that, serves as a protective covering. When the environment is again suitable, the envelope, ruptures, and the amoeba emerges., 5. Following the drying of their pond, the Salamanders inhabit cracks and crevices in the dried, mud at depths of 15–30 cm for 1–2 months during the summer, thereby, requiring, salamanders to remain below the surface until the next heavy rainfall., 6. With the drying of these pools, C. alboguttata (a medium-size frog of eastern Queensland), burrows into the substrate, forms a cocoon of shed layers of epithelium and mucus, and, remains dormant for up to 10 months., 7. For reptiles, aestivation (or aestivation-like behaviour) has been reported for species of, turtles, lizards, snakes, and crocodilians. At the start of the dry season, individuals will, bury into the mud or move into crevices, burrows, or under leaf litter. They remain, relatively inactive and do not feed until the next significant rainfall., , *****, , “Drop by drop is the water pot filled. Likewise, the wise man, gathering it little by little, fills, himself with good”., Buddha, , “When a sieve is shaken, the refuse remains; so a man's filth remains in his thoughts”., Sirach, , 22, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , s, , CHAPTER – 04, , DIGESTION, , HUNGER:, Hunger is a feeling of discomfort or weakness caused by lack of food, coupled with the desire to, eat or drink., APPETITE:, It is a sensation experienced with desire for food or drink., , DIGESTION AND ABSORPTION OF CARBOHYDRATES:, Dietary carbohydrates principally consist of the polysaccharides (starch, glycogen, etc.),, disaccharides (lactose, maltose, sucrose, etc.) and small amounts of monosaccharide (glucose,, fructose, ribose, etc.)., Liquid food like milk, soup, fruit juice escape digestion in mouth as they are swallowed; but solid, food stuffs are masticated thoroughly before they are swallowed., Digestion in mouth:, Digestion of carbohydrates starts at the mouth, where the food comes in contact with saliva upon, mastication. The tongue rotates the food and mix the saliva., Saliva contains a carbohydrate splitting enzyme called salivary amylase (ptyalin)., , 23, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Salivary amylase hydrolyses α (1-4) glycosidic linkage at random deep inside the polysaccharide, molecule like starch and glycogen, producing smaller monomeric molecules like glucose and, disaccharides., , Starch / Glycogen, , Salivary amylase, , Glucose + Maltose, , pH 6.7, , Digestion in stomach:, There are no carbohydrate digesting enzymes present in the gastric juice, thus, in the stomach there, is no carbohydrate digestion by the enzymatic activity. But, some of the dietary sucrose may get, hydrolysed to glucose and fructose by HCl., , Sucrose, , HCl, , Glucose + Fructose, , Digestion in small intestine:, The bolus reaches the duodenum from stomach where it meets the pancreatic juice. Pancreatic juice, contains a carbohydrate slitting enzyme pancreatic amylase (also called amylopsin). Amylopsin, digests the remaining undigested starch or glycogen into maltose and isomaltose., , Starch / Glycogen Pancraetic amylase, pH 7.1, , Maltose + Isomaltose, , The intestinal juice of the brush boarder cells of the small intestine contains maltase, iso-maltase,, lactase and sucrase enzymes. These enzymes are called brush boarder enzymes, by the activity of, these enzymes, the disaccharides are converted into monomeric units like glucose, fructose,, galactose, etc., , 24, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , Maltose, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Maltase, , Glucose + Glucose, , pH 5.8 - 6.2, , Isomaltose, , Isomaltase, , Glucose + Glucose, , pH 5.8 - 6.2, , Lactose, , Lactase, , Glucose + Galactose, , pH 5.4 - 6.0, , Sucrose, , Sucrase, , Glucose + Fructose, , pH 5.0 - 7.0, , Note: Cellulose digestion in human is absent due to the absence of cellulase enzyme., Absorption of carbohydrates:, In the small intestine, all the complex carbohydrates like starch and glycogen and the disaccharides, are ultimately, converted to simpler monosaccharide., All monosaccharide, are practically completely absorbed from the small intestine. No, carbohydrates higher than the monosaccharide can be absorbed directly into the blood stream., There are two ways for the absorption as follow;, Simple diffusion: this is depending on sugar concentration gradients between the intestinal lumen,, mucosal cells and blood plasma. All the monosaccharide is probably absorbed to some extent by, simple ‘passive’ diffusion., Active transport:, Glucose, fructose and galactose are absorbed rapidly by means of sodium dependent active, transport mechanism in the presence of carrier protein and with the expenditure of energy., , 25, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Then carrier protein has two binding sites. The binding sites of the carrier protein are occupied by, Glucose and Na+, thus the transport of glucose proceeds. After reaching the cytosol of the intestinal, cell they get dissociate. The sodium is pumped back to the lumen by Sodium pump with the, expenditure of energy., , DIGESTION AND ABSORPTION OF PROTEINS:, Proteins which we take in our diet are either from animal source or plant source. Principal animal, sources are milk, meat, fish, liver, eggs, etc., and plant sources are cereals, pulses, peas, beans, nuts,, etc., Digestion in mouth:, There are no proteolytic enzymes in mouth, therefore protein digestion is absent in mouth. After, mastication the bolus of food reaches stomach where it meets the gastric juice., , 26, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Digestion in stomach:, The gastric juice contains a number of proteolytic enzymes. They are Pepsin, Rennin, Gastriscin and, Gelatinase., Pepsin is secreted as inactive form, Pepsinogen. It is hydrolysed and thus activated by HCl. The, pepsin hydrolyzes peptide bonds of protein molecules and produce large polypeptides., , Pepsinogen, (Inactive), , HCl, , Pepsin, , Protein, , pH 1.6 -2.5, , Pepsin, (Active form), , Large Polypeptide, , Digestion in small intestine:, The bolus of food after leaving stomach reaches duodenum, where it meets pancreatic juice. The, pancreatic juice contains pancreatic enzymes like Trypsin, Chymotrypsin, and Carboxypeptidases, in inactive forms., Initially, the intestinal juice is secreted by the intestinal cells (enterocytes) contain Enterokinase, enzyme which activates Trypsinogen into Trypsin., , Trypsinogen, (Inactive), , 27, , Enterokinase, pH 5.5, , Trypsin, (Active), , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Tripeptides, , Tripeptidase, pH 7.0 - 8.0, , Dipeptides, , Amino acids, , Dipeptidase, pH 7.0 - 8.0, , Amino acids, , Absorption of proteins:, Amino acids are absorbed from ileum and distal jejunum. Dipeptides and tripeptides are absorbed, from duodenum and proximal jejunum., Amino acids are coupled with Na+ and are absorbed with the help of carrier protein. Di- and, tripeptides are absorbed along with the H+ then in the cytosol of the cell they get hydrolysed into, amino acids. Later, all the amino acids diffused into blood stream. Through the blood amino acids, reach liver and muscle where they get stored., For every entry of one Na+, one H+ move out of the cytosol into the lumen. Thus, maintain the ionic, equilibrium., , 29, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , DIGESTION AND ABSORPTION OF LIPIDS:, The chief dietary source of lipid in human beings are animal sources like-milk, butter, ghee, meat,, fish, eggs, and plant sources like-oils from various seeds, etc., Digestion in mouth:, It was believed earlier that little or no lipid digestion take place in the mouth. Recently, a lipase has, been detected called lingual lipase which is secreted by the dorsal surface of the tongue., Lingual lipase activity is optimum at pH 4.0-4.5., therefore, its activity continued in the stomach, where the pH value is low (acidic)., , Triacylglyceride, (TAG), , Lingual Lipase, pH 4.0 - 4.5, , Fatty acids, , Digestion in stomach:, In the stomach, due to the retention of food bolus for 2-3 hours, about 30% of Triacylglyceride, (TAG) may be digested by the activity lingual lipase., The gastric lipase in gastric juice digest negligible amount of dietary lipid, because the gastric, lipase activity is more effective at relatively alkaline pH 7.8., , Triacylglyceride, (TAG), , Gastric Lipase, , Fatty acids, , pH 7.8, , Digestion in small intestine:, The major site of lipid digestion is the small intestine. This is due to the powerful lipases in the, pancreatic juice and presence of bile salts, which acts as an effective emulsifying agent for lipid., , 30, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , On the entry of acidic chyme from the stomach into intestine, the intestinal cells (Brunner’s gland), secret Cholecystokinin (CCK) and Secretin., Cholecystokinin causes contraction of gall bladder and discharge the bile into duodenum as well, as induce secretion of pancreatic juice from pancreas; whereas, Secretin increases the secretion of, electrolytes and fluid components of pancreatic juice., , Contraction of, Gall bladder, , Stimulate the, Pancrease, , Induced by CCK, , Induced by Secretin, , Bile juice secretion, into Duodenum, , Electrolytes + Pancreatic juice secretion, , Bile salts help in emulsification of fat. Emulsification is a process of breaking up of large lipid, molecules into much smaller droplets by the activity of bile salts., The bile salts coated mixture of Triacylglyceride, Cholesterol ester, Phospholipids and fat soluble, Vitamins A, D, E and K called “micelles”., Pancreatic juice contains number of lipolytic enzymes like- Pancreatic lipase, Cholesterol, esterase, Phospholipase, etc., Pancreatic lipases act on Triacylglycerides and form fatty acids and Glycerol., , Triacylglyceride, (TAG), , Pancratic Lipase, , Fatty acids + Glycerol, , pH 7.8, , Cholesterol esterase acts on Cholesterol ester and form Cholesterol and fatty acids., , Cholesterol, esters, , 31, , Cholesterol Esterase, , Fatty acids + Cholesterol, , pH 7.8, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Phospholipases acts on phospholipids and produce Lysophospholipid and fatty acids., , Phospholipids, , Phospholipase, , Fatty acids + Lysophospholipid, , pH 7.8, , Now the emulsion of droplet contains mixtures of Diglycerides, monoglycerides, fatty acids,, cholesterol, Lysophospholipids and Fat soluble vitamins called “mixed micelles”., Absorption of lipids:, Diglycerides, , (DG),, , monoglycerides, , (MG),, , fatty, , acids, , (FA),, , Phospholipids, , (PL),, , Lysophospholipids (LPL), Fat soluble vitamins are directly pass across the membrane by simple, diffusion but the cholesterol (CHL) is absorbed by active transport with the utilization of ATP., All the absorbed constituents of lipid move to liver, arteries, adipocytes and stored., , ********, , 32, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 05, , RESPIRATION, , Respiration is a physiological process in which the intake of oxygen (O) and output of Carbon dioxide, (CO2). The oxygen is used in the oxidation of digested food in the cell to liberate energy. CO 2 is, produced as a result of the oxidation of food materials. Carbon dioxide produced in the oxidation of, food is harmful therefore it has to be removed from the body during respiration., Respiration is an essential physiological activity of all living organisms by which they obtain energy, for carrying out all other metabolic activities of the body., PHYSIOLOGY OF RESPIRATION:, EXCHANGE OF GASES OR TRANSPORT OF GASES:, Atmospheric air enters the lungs by inspiration from the lungs oxygen diffuses into the blood., The blood carries the oxygen to the cells. The cells take up oxygen for oxidation. Oxidation releases, carbon dioxide. The carbon dioxide is carried to the lungs for removal., “The transport of Oxygen from the lungs to the cells and the transport of carbon dioxide from, the cells to the lungs”, is known as transport of gases., TRANSPORT OF OXYGEN:, 1. The transport of oxygen from the lungs to the cells is called oxygen transport., 2. The lungs contain atmospheric air, from the lungs oxygen diffuses into the blood., 3. The blood transports oxygen from the lungs to the cells., 4. The oxygen is transported by Haemoglobin (Hb) present in the RBC of blood., , 33, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 5. The arterial blood contains 20ml of oxygen per 100ml of blood. The venous blood contains, 15ml of oxygen per 100ml of blood., 6. The Oxygen carrying capacity of blood will be higher when the blood contains more, Haemoglobin., 7. When the oxygen pressure in the blood is high. Haemoglobin is loosely attaches with oxygen, to form oxyhaemoglobin (HbO2). Similarly, it dissociates (separates) readily with oxygen,, when the oxygen pressure is lesser in the blood., , Haemoglobin + Oxygen, , In lungs, , Oxyhaemoglobin, , In tissues, , Haemoglobin + Oxygen, , 8. In alveolar capillaries of lungs, the oxygen pressure is higher; hence here Hb combines with, oxygen to form oxyhaemoglobin (HbO2). Each Hb molecule combines with 4 molecules, oxygen., 9. The blood leaving the lungs has 99% of its Hb is fully loaded with oxygen when the blood, is fully loaded with oxygen it carries 20ml of oxygen per 100ml of blood., 10. From the lungs the oxygen rich blood enters the heart and is then pumped to the various, organs. The cells present in the tissue of various organs consume oxygen continuously. Hence, the oxygen presence in the tissues and organs will be lesser., 11. When the oxygen rich blood passes through the tissues. Hb dissociates from oxygen., 12. The oxygen diffuses out from the blood through capillary wall & enters the tissues., 13. The Hb returns to the lungs and again transports new oxygen molecules., 14. The venous blood contains 15ml of O2 /100ml of blood., , 34, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , OXYGEN DISSOCIATION CURVE:, Oxygen dissociation curve is a graph showing the proportion of oxyhaemoglobin and oxygen, pressure., 1. Hb can combine with oxygen to form oxyhaemoglobin., Hb  O2  HbO2, , 2. When the oxygen partial pressure is low, the percentage of HbO2 formed will also be, lesser that is at low partial pressure of oxygen the affinity of Hb for oxygen will be lesser., , 10 20 30 40 50 60 70 80 100, , % of haemoglobin with Oxygen, , When the oxygen pressure is high the percentage of HbO2 formed will be higher., , 0, , 20, , 40, , 60, , 80, , 100 120 140 160, , Partial pressure of O2 (mmHg), , 3. It is ‘S’ or sigmoid shaped curve. The dissociation curve for human blood and pure, Haemoglobin are given in the figure., 4. The curve for blood clearly shows that at zero mmHg of Oxygen pressure the percentage, of HbO2 formed is also zero., 5. At 30mm Hg of oxygen pressure the percentage of HbO2 formed is about 55 and at 70mm, Hg of O2 percentage HbO2 90., 6. At 90mm Hg, the percentage of HbO2 formed is 98%., 7. This curve clearly shows that when the oxygen pressure increases the percentage of HbO2, formed is also increased. However, above 100mm Hg there is only of slight increase in the, percentage of the oxyhaemoglobin., 35, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , BOHR EFFECT:, “High concentration of carbon dioxide in the tissues helps to unload oxygen from, oxyhaemoglobin (HbO2)”, is called Bohr Effect., 1. Carbon dioxide concentration is higher in the tissues. When blood containing HbO2 passes, through the tissues, the affinity of Hb for oxygen is reduced because of higher concentration, of carbon dioxide in the tissue. Hence Hb separates from oxygen and oxygen is released for, the utilization of tissues., 2. Thus, increasing concentration of carbon dioxide helps to unload oxygen from HbO2., 3. As a result of Bohr Effect the dissociation curves move to the right. The dissociation curves, , 8, 20, 40, , mmHg pCO2, , 3, , 10 20 30 40 50 60 70 80 100, , % of haemoglobin with Oxygen, , for different concentration of carbon dioxide are given in figure., , 90, , 0, , 20, , 40, , 60, , 80, , 100 120 140 160, , Partial pressure of O2 (mmHg), , 4. At high carbon dioxide pressures the oxygen pressure at which haemoglobin becomes, saturated with oxygen is higher than it is at low carbon dioxide pressures. In the tissues,, addition of carbon dioxide is given out from the blood, uptake of oxygen is facilitated., 5. The direct effect of CO2 on the oxyhaemoglobin dissociation arises from its combination with, the amino terminal of the haemoglobin sub units to from carbamino haemoglobin, which, has decreased affinity for oxygen. Thus, its formation shifts the curve to right., , 36, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , TRANSPORT OF CARBON DIOXIDE:, “The transport of carbon dioxide from the tissues to the lungs through the blood”, is called, carbon dioxide transport., Carbon dioxide is carried in blood in 3 ways;, 1. As Carbonic acid:, About 5% of carbon dioxide dissolves in plasma to form carbonic acid (H2CO3) and it is, carried to the lungs. In the lungs the reaction is reversed to release carbon dioxide., , CO2 + H2O, , In tissues, , H2CO3, , In lungs, , CO2 + H2O, , 2. As carbamino complex:, About 10% of carbon dioxide is carried as carbamino compound. Carbon dioxide combines, with the amino group of plasma protein to form carbamino complex. These compounds are, carried to the lungs where the reaction reversible., , R-NH2 + CO2, , In tissues, , R-NH-COOH, , In lungs, , R-NH2 + CO2, , 3. As bicarbonates:, About 85% of Carbon dioxide is transported as bicarbonates in RBC as well as in plasma., Most of the carbon dioxide entering the blood from the tissues diffuses into the RBC. In the, RBC, carbon dioxide combines with water to form carbonic acid (H2CO3). In the RBC this, reaction accelerated by an enzyme called carbonic anhydrase. The carbonic acid is unstable, & immediately it dissociates into hydrogen ions & bicarbonates (HCO3–)., , CO2 + H2O, , 37, , In tissues, , H2CO3, , In lungs, , H+ + HCO-3, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , The hydrogen (H+) ions released from the carbonic acid cannot be retained as such in the, RBC. It readily combines with HbO2., HbO2 + H+, , In tissues, , HHb, , In lungs, , Hb + H+, , O2, , The blood leaving the tissues contains large quantities of HCO3& reduced haemoglobin, (HHb) & small amount of carbonic acid No further changes lungs place until the blood reaches, the capillaries, , CHLORIDE SHIFT OR HAMBURGER’S PHENOMENON:, The excess HCO3 leaves the red cells in exchange for Cl–, this exchange is called the chloride shift., , [OR], “The movement of chloride ions from the plasma into RBC as a result of transfer of carbon, dioxide from tissues to the plasma”., 1. From the tissue cells, carbon dioxide diffuses into RBC through plasma., 2. In RBC, CO2 combines with H2O to form H2CO3., 3. The H2CO3 immediately ionizes into H+&HCO3-., 4. Bicarbonates ions  HCO3  are negatively charged and they diffuse into the plasma from RBC,, thus RBC becomes positively charged., 5. In order to maintain neutrality, negatively charged chloride ions (Cl–) diffuses into the RBC, from plasma. This phenomenon is called chloride shift., 6. Chloride shift provides advantage in transportation of carbon dioxide by forming more, bicarbonates and carbon dioxide carrying capacity of RBC is increased by chloride shift., 7. Chloride shift is extremely rapid, occurring within one second., , 38, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 8. The chloride shifts results in the chloride content of venous blood being greater than that, of arterial blood., 9. Carbonic anhydrase enzyme in RBC catalysis the conversion of carbon dioxide to carbonic, acid which is not highly expressed in interstitial fluid & plasma., 10. Chloride shift also regulate the affinity of haemoglobin for oxygen through chloride ion acting, as an allosteric effector., , CO2, pCO2 = 45 mmHg, , Tissue/Cell, , pCO2 = 40 mmHg, , CO2, , CO2 + H2O, , Carbonic, anhydrase, , HCO3-, , H2CO 3, , H+ + HCO -3, , Plasma of the Blood, , ClCl-, , HbO2 + H+, , HHb + O 2, , RBC, , RESPIRATORY QUOTIENT (RQ):, Respiratory quotient (RQ) is, “the ratio of volume of carbon dioxide released from the lungs over, the volume of oxygen absorbed from the lungs in one minute”., , RQ , , CO2 e liminated, O2 consumed, , From this ratio considerable information can be gathered about the nutrients being metabolized. If, pure food stuffs are burnt, their RQ can be measured directly with pure carbohydrate it is 1., , 39, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , C6H12O6  6O2  6CO2  6H2O  Energy  Heat,  Glu cos e , , Rq , , 6CO2 6,   1.0, 6CO2 6, , CELLULAR RESPIRATION:, The oxygen liberated from the dissociation of oxyhaemoglobin in the tissue-cells is utilized in the, oxidation of food molecules to liberate energy along with CO2 and H2O, So all the reactions taking place in the cell (mitochondria) to liberate energy is called cellular, respiration or Tissue respiration. Free energy is the energy available to do work. Main energy rich, compounds are ATP, ADP, and NADH2 etc., Biological oxidation takes place by removal of electrons & union between Hydrogen and oxygen, atoms. Biological Oxidation occurs in following steps., 1. Glycolysis, 2. Oxidative decarboxylation, 3. Krebs cycle, 4. Electron Transport System, 5. Oxidative phosphorylation, GLYCOLYSIS:, Glycolysis occurs in Cytoplasm., Glycolysis is known as EMP pathway after the names of German Scientists Embden, Meyerhof and, Paranas, who discovered Glycolysis., , 40, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Glycolysis is the first step of cellular respiration that brings about partial oxidative breakdown of, Hexose sugar (glucose) into two molecules of Pyruvic acid. Through enzyme mediated reactions., Steps of Glycolysis:, 1. During Glycolysis, glucose in the cell is phosphorylated by ATP in the presence of, glycohexokinase to form glucose-6-phosphatewith the utilization of one ATP. (**Glycogen, can also be converted in glucose-6-phosphate by Glycogenolysis. **), 2. Glucose-6- phosphate is then converted into fructose-6-phosphate by the enzyme, phosphate isomerase., 3. Fructose-6-phosphate is phosphorylated by ATP in the presence of phosphofructokinase to, formfructose-1,6-bisphophatewith the utilization of one ATP., 4. Thenfructose-1,6-bisphophate is split by enzyme fructo aldolase into two substrates namely, glyceraldehydes-3-phosphate&dihydroxyacetone phosphate. There two substrates are, inter-convertible in the presence of triose isomerase., 5. The two molecules of glyceraldehydes-3-phosphosphate are phosphorylated & oxidized, into 1, 3-diphosphoglyceric acid by phosphoglyceric dehydrogenase; with the reduction of, NAD+ to NADH2., 6. 1,3-diphosphoglyceric acids is converted into 3-phosphoglyceric acid by means of 3phosphoglycerate kinase with the synthesis of one ATP., 7. 3-phosphoglyceric acid is converted into 2-phosphoglyceric acid by the enzyme, phosphoglyceromutase., 8. 2-Phosphoglyceric acid is converted into phosphor-enol-pyruvic acid by dehydration in the, presence of enolase., 9. The phospho-enol-pyruvic acid now forms pyruvic acid by pyruvic kinase with the synthesis, of one ATP., , 41, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , OXIDATIVE DECARBOXYLATION:, It is a process of oxidation where–pyruvic acid is converted into Acetyl Co-enzyme A., The pyruvic acid produced in the particles located on the outer membrane of the mitochondria., This complex particle called pyruvic acid dehydrogenase with the help of this enzyme pyruvic acid, undergoes decarboxylation & oxidation., During decarboxylation carbon dioxide is removed from pyruvic acid as a result pyruvic acid, converted into Acetyl CoA., Pyruvic acid + CoA  Acetyl CoA + CO2 +H2, The release of H+ atoms are accepted by NAD & reduced to NADH2., NAD+ + H2 NADH2, KREB’S CYCLE:, This cycle described by Krebs in 1936.The oxidation of pyruvic acid into carbon dioxide and water, is called Krebs cycle. Here in the beginning formation of citric acid take place hence called ‘citric, acid cycle’& citric acid contains 3 COOH groups hence called Tricarboxylic acid cycle. This cycle, occurs only in the presence of Oxygen. So it is aerobic process. It occurs mainly in the mitochondria., Steps involved in TCA cycle:, 1. Acetyl CoA combines with Oxaloacetic acid (OAA) to form citric acid. It is catalyzed by, citric acid synthetase., 2. Citric acid undergoes dehydration& forms isocitrate, with the help of isomerase enzyme., 3. Isocitrate undergoes decarboxylation in the presence of citric acid dehydrogenase to formketoglutarate with the liberation of CO2. Here 2 hydrogens are released they are accepted by, NAD+ to form NADH2., , 43, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , OXIDATIVE PHOSPHORYLATION:, 1. It is the synthesis of energy rich, ATP from ADP and inorganic, phosphate (Pi)., 2. It, , takes, , mitochondria;, , place, , in, , the, , between, , the, , mitochondrial space and matrix, of the mitochondria., 3. Proton gradient Driven ATP Synthesis: Proton gradient (or) Proton motive force tends to, push the protons from outer mitochondrial chamber towards the mitochondrial matrix through, the inner membrane., 4. Inner membrane is permeable to protons only in the region of F0 or bases of elementary, particles (F0–F1). They function as proton tunnels (or) channels., 5. Stalk region of elementary particles has coupling factors while F1 head piece has enzyme, ATPase that catalysis ATP synthesis., 6. 2 Protons are required for synthesis of 1 molecule of ATP, 7. They knockout one oxygen of inorganic phosphate and convert the latter into active phosphate, (Energy rich phosphate); the latter immediately combines with ADP to form ATP or ADP +, Pi., 8. Since NADH (H+) drives out 3 pairs of protons to outer chamber, its oxidation is linked to, synthesis of 3 ATP molecules., 9. Similarly, oxidation of FADH2 that causes pumping of two pairs of protons forms 2 ATP, molecules., 10. ATP molecular synthesized inside mitochondria come out of the latter through facilitated, diffusion across inner membrane & diffusion across outer membrane., , 45, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , ENERGY BUDGET: (Energetic of Glucose metabolism or Respiratory Balance Sheet), It is possible to make calculation of net gain of ATP molecules for every glucose molecule oxidized., This calculation is theoretical & based on certain assumptions., a) Respiratory pathway is going on sequentially & orderly- Glycolysis Krebs cycle and Electron, Transport System., b) NADH produced in glycolysis is transferred to mitochondria for oxidative phosphorylation., c) None of the intermediates is used in any other metabolic activity., d) Only hexose sugar Glucose is being used as substrate., e) Enzymes control the reactions., , ENERGY BUDGET, Metabolic Pathway, , Glycolysis, , Oxidative Decarboxylation, , Kreb's Cycle, , Reaction, , Formation, , Total ATP, , Glucose to Glucose-6-Phospate, , (-) 1 ATP, , Fructose-6-Phosphate to Fructose-1,6-Phosphate, , (-) 1 ATP, , Glyceraldehyde-3-Phosphate, , 2 x NADH2, , (+) 6 ATP, , 1,3-Diphosphoglyceric acid to 3-Phosphoglyceric acid, , 2 x ATP, , (+) 2 ATP, , Phospho-enol Pyruvic acid to Pyruvic acid, , 2 x ATP, , (+) 2 ATP, , Pyruvic acid to Acetyl CoA, , 2 x NADH2, , (+) 6 ATP, , Iso-citrate to Keto-Glycerate, , 2 x NADH2, , (+) 6 ATP, , Keto-Glycerate to Succinyl CoA, , 2 x NADH2, , (+) 6 ATP, , Succinyl CoA to Succinic acid, , 2 x ATP, , (+) 2 ATP, , Succinic acid to Fumerate, , 2 x FADH2, , (+) 4 ATP, , Malate to Oxalo Acetic Acid, , 2 x NADH2, , (+) 6 ATP, Grand Total, , 8 ATP, , 6 ATP, , 24 ATP, , 38 ATP, , *******, , 46, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 06, , CIRCULATION, , STRUCTURE AND FUNCTION OF HUMAN HEART:, , 1. It is hallow- fibro-muscular, conical organ, lies in the thoracic cavity in between the lungs., 2. It is reddish-brown in colour., 3. Adult heart is equal to the size of the clinched fist. It about 12 cm in length, 8-9 cm in breadth, and thickness is about 6 cm., 4. Heart is primarily made up of cardiac muscle called myocardium., 5. Heart is enclosed in pericardium; the pericardial cavity is filled with pericardial fluid which, protects the heart from any kind of external jerk or shock., 6. Human heart is four chambered; having two auricles and two ventricles., 47, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 7. The right and left auricles are separated by a fibrous partition called interatrial septum., Similarly, the right and left ventricles are separated by a fibrous partition called, interventricular septum., 8. The auricles are separated from ventricles by auriculo-ventricular septum., 9. The right auricle opens into right ventricle by a right auriculo-ventricular aperture and it, is guarded by tricuspid valve., 10. The left auricle opens into left ventricle by a left auriculo-ventricular aperture and it is, guarded by bicuspid valve., 11. The bicuspid and tricuspid valves prevent the back flow of blood from ventricles into the, auricles., 12. The systemic aorta and the pulmonary aorta are guarded by semilunar valves. Each of the, semilunar valves is made up of three, half-moon-shaped cusps. These valves prevent the, back flow of blood from the aorta into the respective ventricles., 13. Right auricle receives deoxygenated blood from the body parts through the superior and, inferior vena-cava., 14. Right ventricle pumps the deoxygenated blood to the lungs through the pulmonary aorta,, for purification (oxygenation)., 15. Left auricle receives oxygenated blood from the lungs through the pulmonary veins., 16. Left ventricle pumps the oxygenated blood to all the body parts through the systemic aorta., 17. The myocardium has variable levels of thickness within the heart., a. Chambers of the heart with a thicker myocardium are able to pump blood with, more pressure and force compared to chambers of the heart with a thinner, myocardium., b. The myocardium is thinnest within the atria, as these chambers primarily fill, through passive blood flow., c. The right ventricle myocardium is thicker than the atrial myocardium, as this, muscle must pump all blood returning to the heart into the lungs for oxygenation., 48, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , d. The myocardium is thickest in the left ventricle, as this chamber must create, substantial pressure to pump blood into the aorta and throughout systemic, circulation., 18. There are three types of blood vessels; arteries, veins and capillaries., a. Arteries are the thick walled vessels; they carry blood away from the heart to the body, parts and lungs., b. Veins are the blood vessels; which carry blood towards the heart from the body parts and, the lungs., c. Capillaries are the branches of the blood vessels and they are the connective link, between the arteries and the veins., , REGULATION OF HEART BEAT:, , 49, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 1. The contraction of the heart called systole and the relaxation of the heart is called diastole., The systole and the diastole together constitute heartbeat., 2. The sequence of one systole is followed by one diastole is termed as cardiac cycle., 3. In each heartbeat, each ventricle pumps out about 70 ml blood. This volume is called stroke, volume., 4. The heart beats about 72 times per minute; is called heart rate or pulse rate., 5. The sinu-auricluar node (SA Node) has a rich supply of capillary blood, also known as Pace, maker. The heart beat is initiated by this special tissue. Hence the pace maker is sometime, referred as ‘Heart of Heart’., 6. The impulse arising from the SA Node is picked up by Auriculo-ventricular node (AV, node)., 7. From the SA node the impulse is carried by Bundle of His and Purkinje fibers, to the various, regions of the ventricle., 8. A cardiac cycle has three phases;, a. Phase I: simultaneous contraction of both of the auricles pump the blood from the, auricles into the ventricles (ventricles are in relaxing state)., b. Phase II: phase I is followed by simultaneous contraction of both ventricles, thus force, the blood into the aorta, (now the auricles are in relaxing state)., c. Phase III: both the auricle and the ventricles are in relaxed state called general pause*., 9. The three phases of one Cardiac cycle takes 0.8 seconds; in which both the auricle and, ventricle remain the condition of diastole (relaxed) i.e., the heart take rest for 0.4 seconds., This stage is called general pause., , 50, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , BLOOD PRESSURE (BP):, “The lateral pressure that the blood exerts against the walls”, called blood pressure., 1. The pressure existing in the arteries, called arterial pressure., 2. The blood pressure is high during systole and is called systolic blood pressure., 3. The blood pressure is low during diastole and is called diastolic blood pressure., 4. The blood pressure is –, *high in the aorta situated near the heart,, **the pressure becomes low in the capillaries and, ***becomes minimum in the veins., 5. The normal blood pressure ranges between 120/80 mmHg (read as 120 over 80 mmHg)., (i.e., the diastolic blood pressure is 80 mmHg and the systolic blood pressure is 120 mmHg)., 6. High blood pressure (Hypertension): hypertension is a state where the blood pressure rises, and sustained at high level., e.g., a BP of 170/150 mmHg for 70-yearold person will be considered as hypertension., 7. Low blood pressure (Hypotension): hypotension is the condition of decrease in blood, pressure below the normal., e.g., a BP of 100/50 mmHg for a person will be considered as hypotension., 8. Sphygmomanometer is the instrument used to measure blood pressure., , MECHANISM OF BLOOD CLOTTING:, 1. According to Best and Taylor, four substances are necessary for blood clotting. They, are prothrombin, calcium, Thromboplastin, and fibrinogen., 2. Prothrombin is produced by the liver and is also present in small quantities in, the plasma of blood. Vitamin-K helps in the synthesis of prothrombin in the liver., 51, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 3. Calcium ions are present in the plasma as inorganic constituents., 4. Fibrinogen is a soluble protein found dissolved in the plasma., 5. When an injury is formed, thromboplastin is liberated from the injured tissue., 6. The released thromboplastin acts on prothrombin in presence of calcium ions and converts, it into active thrombin., 7. The thrombin in its turn acts upon fibrinogen, converting it into fibrin., 8. The blood cells are entangled within fibrin thread to form a clot., 9. The blood within the blood vessels never clots., 10. If clotting occurs in the blood vessels it is called thrombosis and the clot is known as a, thrombus., 11. However, the blood clotting in blood vessels is prevented by antithrombin that is heparin., Heparin is also produced from the liver and present in the blood., , Liver, , Prothrombin, , Injured Muscle Cells, , Thromboplastin, , Calcium ions, , Thrombin, , Fibrinogen, (Soluble), , Fibrin, (Insoluble), , Blood Clot, , “True EDUCATION reflects in the BEHAVIOUR and NATURE of People”., Subhajit Sarkar, 52, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 07, , NITROGEN EXCRETION, , Excretion is the elimination of metabolic waste products and excess metabolites from the body of an, organism in order to maintain homeostasis., TYPES OF NITROGEN EXCRETION:, Nitrogen as such will not be present in the body; it will combine with some other chemical substances., On the basis of types of nitrogenous waste excretion, the animals are classified into the following, types;, AMMONOTELISM:, Most of the aquatic animals excrete nitrogenous waste in the form of ammonia and ammonia ions;, the process is called ammonotelism and the animals are called ammonotelic animals., Ammonia is highly toxic and water soluble. It requires a lot of water for elimination as ammonia, cannot be concentrated due to its toxicity,, e.g., protozoans, earthworm, octopus, fishes, tadpoles of amphibia, etc., UREOTELISM:, Most of the terrestrial animals excrete nitrogenous waste in the form of urea; the process is called, ureotelism and the animals are called ureotelic animals., Urea is less toxic than ammonia and water soluble but can be concentrated to some extent., e.g., human, camel, shark, kangaroo rat, etc., , 53, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , URICOTELISM:, Some of the animals excrete nitrogenous waste in the form of uric acid; the process is called, uricotelism and the animals are called uricotelic animals., Uric acid is less toxic and less soluble in water., e.g., insects, lizards, snakes and birds, GAUNOTELISM:, In few animals excrete nitrogenous waste in the form of guanine, the process is called guanotelism, and the animals are called guanotelic animals., e.g., scorpions and spiders, ORNITHINE CYCLE:, , 54, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 1. Urea is a nitrogenous compound formed by the combination of two molecules of ammonia, and one molecules of carbon dioxide, with the elimination of water., CO2  2NH2 ,  C  O  H 2O, , 2. Ammonia combines with CO2, form carbonyl phosphate in the presence of carbamyl, phosphatesynthetase. This is energy expenditure step (two ATPs are utilized)., 3. The carbamoyl group is then transferred to ornithine in the presence of trans-carbamoylase, to form citrulline., 4. Citrulline couples with aspartic acid and form argino-succinic acid with the utilization of, ATP., 5. Argino-succinic acid then splits into arginine and fumeric acid., 6. Arginine yields urea and ornithine in the presence of arginase. The urea is eliminated as a, nitrogenous waste, while ornithine once again combines with NH3 and CO2 and repeats the, cycle., 7. The fumeric acid formed during this cycle is converted into malic acid and then to, Oxaloacetic acid., , NITROGEN EXCRETION IN RELATION TO WATER ECONOMY:, 1. The elimination of nitrogen is a process technically known as excretion. Excretion is a, necessary consequence of protein breakdown., 2. In the body, the amino group is quickly oxidized to form ammonia (or, at high body pH the, ammonium ion). Ammonia is highly toxic and highly soluble in water., 3. If the organism has a sufficient source of water, ammonia can simply have excreted in the, water. This is the course taken by many (if not most) aquatic organisms, particularly those in, freshwater. In any event, ammonia must be dealt with quickly because of its toxicity., 55, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 4. Ammonia will diffuse passively out of respiratory structures such as gills. It takes a lot of, water to dissolve and flush ammonia, however, and each ammonia molecule carries only, one nitrogen., 5. Organisms with less fresh water available, such as some marine organisms and all terrestrial, organisms, are not as likely to waste water excreting nitrogen one atom at a time. They, will often invest some energy to convert the ammonia into urea, which is less toxic, has two, nitrogen atoms, and therefore takes less water to excrete., 6. Because Urea is less toxic, it can be allowed to accumulate in the blood to some extent, and, many organisms have specialized organs to remove urea and other wastes from the blood and, excrete them. Urea is commonly used as an excretory product in vertebrates, and is rarely, used in invertebrates., 7. Some organisms, such as sharks and snails, allow urea to accumulate in their blood to help, with overall osmotic balance. Sharks, for instance, use urea in the blood to make them, hyperosmotic in relation to seawater, thus they tend to gain water from the ocean and do not, have to worry about dehydration., 8. Some organisms go to greater lengths still to deal with nitrogen. Where water is at a real, premium, even the low toxicity and reduced water loss possible with urea excretion is not, enough. Uric acid is even less toxic than urea, and it precipitates from solution, allowing, the 4 nitrogen atoms per uric acid molecule to be excreted with just enough water so that the, crystals don't scratch on the way out., 9. It has evolved in two groups with major water loss problems - terrestrial invertebrates and, egg-laying vertebrates (obviously an embryo can't just step out for a drink, and whatever it, excretes is going to be very close by until hatching). Figure 1 shows the three common, nitrogenous wastes., 10. Common nitrogenous wastes of animals. Note that for each molecule excreted, ammonia will, carry off 1 atom of N, urea 2, and uric acid 4. Ammonia is the most soluble, followed by urea, and uric acid; the latter actually precipitates out of solution., 56, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , PHYSIOLOGY OF URINE FORMATION IN MAN:, There are three important physiological processes; glomerular filtration, selective reabsorption, and tubular secretion., 1. Glomerular filtration:, This is the initial process in urine formation and it involves the transfer of water and, dissolved substances from the blood into the lumen of the Bowman’s capsule., The fluid in the capsule which is obtained by this process is termed as glomerular filtrate., Glomerular filtrate contains essential material like water, glucose, amino acids, mineral, salts, urea, uric acid, etc. except plasma proteins, lipids and cellular elements of blood., The glomerular filtrate with these materials called primary urine., This filtration is possible because of high blood pressure in the glomerulus called, filtration pressure., 2. Selective reabsorption:, Reabsorption takes place in the uriniferous tubules. It involves the transfer of water and, many dissolved essential substances from the glomerular filtrate into the blood., Reabsorption is selective process, in which, substances like glucose, sodium, calcium along, with water get reabsorbed., Nearly 125 ml of primary urine along with the essential materials get reabsorbed and only, about 1 ml of filtrate flows into distal convoluted tubule (DCT)., Reabsorption takes place by both active and passive transports; water is reabsorbed by, osmosis, while glucose and amino acids are reabsorbed by the active transport., Henle’s loop plays an important role in the reabsorption. As the fluid flows along the, ascending limb NaCl is actively removed and deposited in the descending limb., It plays a key role in homeostasis by the reflection of water, glucose, fats in the blood, , 57, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 3. Tubular secretion:, It takes place in the distal convoluted tubule., As the concentrated filtrate flows through the DCT, the cells of the tubule excrete certain, additional waste material like creatine, sulphates of various salts, ammonia, hydrogenions, and other unwanted substances into the filtrate from the blood stream. This process is called, augmentation., , ******, , 58, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 08, , NEUROPHYSIOLOGY, , STRUCTURE OF MULTIPOLAR NEURON:, 1. A neuron is a structural and functional, unit of the neural tissue and hence the, neural system., 2. Certain neurons have flask-shaped cyton, and are called Purkinje cells, which occur, in the cerebellum of the brain., 3. A neuron consists of main cell body and, cytoplasmic processes arising from it., 4. Cell body (= Cyton or Soma):, a. It varies in size and form. It may be up, to 13.5 µm in diameter and may be, irregular, spherical, oval, rounded,, star-shaped or pyramidal., b. Like a typical cell it consists of cytoplasm, nucleus and cell membrane., c. It has abundant cytoplasm, called neuroplasm and a relatively large spherical central, nucleus with a distinct nucleolus. The cytoplasm has mitochondria, Golgi apparatus,, rough endoplasmic reticulum, ribosomes, lysosomes, fat globules, pigment granules,, neurofibrils, neurotubules and Nissl’s granules., d. The Nissl’s granules (also called Nissl’s bodies) are irregular masses of rough, endoplasmic reticulum with numerous attached and free ribosomes and polysomes. The, Nissl’s granules probably synthesize proteins for the cell., 59, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 5. Neurites:, a. The processes of neurons are called neurites., b. These are of two types: dendrites or dendrons and an axon or axis cylinder or neuraxon., i., , Dendrites (Dendrons): these are usually shorter, tapering and much branched, processes. They may be one to several., , ii., , Axon: axon is a single, usually very long process of uniform thickness. The part, of cyton from where the axon arises is called axon hillock. Most sensitive part of, neuron is axon hillock., The cell membrane of the axon is called axolemma and its cytoplasm is known as, axoplasm. The axon ends in a group of branches, called axon terminals or, telodendria., There are two types of axon namely myelinated and non-myelinated. In, myelinated nerve fibres Schwann cells form myelin sheath around the axon. The, gaps between two adjacent myelin sheaths are called nodes of Ranvier., Myelinated nerve fibres are found in cranial and spinal nerves. In nonmyelinated nerve fibres Schwann cells do not form myelin sheath and are without, nodes of Ranvier. They are commonly found in autonomous and somatic neural, systems., , TYPES OF NEURONS AND NEURO-SYNAPSES:, Neurons may be classified according to the number of their processes into unipolar, bipolar,, pseudopolar and multipolar., , 1. Unipolar Neuron:, Unipolar neurons have only one structure that extends away from the soma. These neurons, are not found in vertebrates, but are found in insects where they stimulate muscles or, glands., 60, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 2. Bipolar Neuron:, A bipolar neuron has one axon and one dendrite extending from the soma. An example of a, bipolar neuron is a retinal bipolar cell, which receives signals from photoreceptor cells, that are sensitive to light and transmits these signals to ganglion cells that carry the signal, to the brain., 3. Pseudounipolar Neuron:, Pseudounipolar cells share characteristics with both unipolar and bipolar cells. A, pseudounipolar cell has a single structure that extends from the soma (like a unipolar cell),, which later branches into two distinct structures (like a bipolar cell). Most sensory, neurons are pseudounipolar and have an axon that branches into two extensions: one, connected to dendrites that receives sensory information and another that transmits this, information to the spinal cord., 4. Multipolar Neuron:, Multipolar neurons are the most common type of neuron. Each multipolar neuron contains, one axon and multiple dendrites. Multipolar neurons can be found in the central nervous, system (brain and spinal cord). The Purkinje cell, a multipolar neuron in the cerebellum, has, many branching dendrites, but only one axon., , 61, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , TYPES OF NEURO-SYNAPSES:, The physiological junction between the axonic ends of one neuron with the dendrites of the other, neuron is called synapse., There are four different types of synapses occur;, a. Axo–dendrite synapse:, This type of synapse occurs between the axon of one neuron, and dendrites of another neuron., b. Axo-axon synapse:, This type occurs a junction between the axons of two neurons., c. Axo- somatic synapse:, This type of synapse occurs between the axon of one neuron, and some (cell body) of another, neuron., d. Dendro-dendrite synapses:, This type of synapse occurs between the dendrite of one neuron, and dendrites of other, neurons., , 62, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , MEMBRANE POTENTIALS (RESTING AND ACTION):, 1. The nerve cells remain bathed in the extracellular fluid (ECF) or interstitial fluid containing a, large amount of sodium chloride and bicarbonates., 2. However, the intracellular fluid (cytoplasm of the neurons) contains a large amount of, potassium and magnesium phosphates in addition to complex proteins and other organic, molecules., 3. Most of the solutes in extracellular fluid and the cytoplasm of the neuron are electrically charged, particles or ions (positively charged cations or negatively charged anions)., , 4. Polarisation (= Resting Potential). In a resting nerve fibre (a nerve fibre that is not conducting, an impulse), the axoplasm (neuroplasm of axon) inside the axon contains high, concentration of K+ and negatively charged proteins and low concentration of Na+., 5. In contrast, the fluid outside axon contains a low concentration of K+ and a high, concentration of Na+ and thus form a concentration gradient. These ionic gradients across, the resting membrane are maintained by the active transport of ions by the sodium-potassium, pump which transports 3 Na+ outwards and 2 K+ inwards (into the cell)., , 6., , As a result, the outer surface of the axonal membrane possesses a positive charge while, its inner surface becomes negatively charged, and, therefore, is polarised. The electrical, potential difference across the resting plasma membrane is called as the resting potential., The state of the resting membrane is called polarised state., , 7. Thus to maintain resting potential sodium-potassium pump operates. In Na+ — K+ pump of, active transport there is efflux of Na+ and influx of K+. It means Na+ is out and K+ is in., , 63, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , AXON MEMBRANE SHOWING RESTING POTENTIAL, , 8. Depolarization: When a stimulus of adequate strength (threshold stimulus) is applied at a, site (Fig. 21.20, e.g., point A) on the polarized membrane, the membrane at the site A, becomes freely permeable to Na+. This leads to a rapid influx of Na+ followed by the, reversal of the polarity at that site, i.e., the outer surface of the membrane becomes, negatively charged and the inner side becomes positively charged., 9. The polarity of the membrane at the site A is thus reversed and hence de-polarised. The, electrical potential difference across the plasma membrane at the site A is called the action, potential, which is in fact termed as a nerve impulse. At sites immediately ahead, the axon, (e.g., site B) membrane has a positive charge on the outer surface and a negative charge on its, inner surface., 10. As a result, a current flow on the inner surface from site A to site B. On the outer surface, current flows from site В to site A to complete the circuit of current flow., 11. Hence, the polarity at the site is reversed and an action potential is generated at site B. Thus,, the impulse (action potential) generated at site A arrives at site B. The sequence is repeated, along the length of the axon and consequently the impulse is conducted., 12. The rise in the stimulus-induced permeability to Na+ is extremely short lived. It is quickly, followed by a rise in permeability to K+. Within a fraction of a second, K+ diffuse outside the, 64, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , membrane and restores the resting potential of the membrane at the site of excitation which is, called repolarization and the fibre becomes once more responsive to further stimulation., , DIAGRAMMATIC REPRESENTATION OF IMPULSE CODUCTION THROUGH AN AXON AT POINT ‘A’ AND ‘B’, , AXONIC AND SYNAPTIC TRANSMISSION OF NERVE IMPULSES:, i., , When an impulse arrives at a presynaptic knob, calcium ions from the synaptic cleft enter, the cytoplasm of the presynaptic knob., , ii., , The calcium ions cause the movement of the synaptic vesicles to the surface of the knob., The synaptic vesicles are fused with the presynaptic membrane and get ruptured, (exocytosis) to discharge their neurotransmitter into the synaptic cleft., , iii., , The synaptic vesicles then return to the cytoplasm of the synaptic knob where they are refilled, with neurotransmitter., , 65, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , TRANSMISSION OF NERVE IMPULSE AT A CHEMICAL SYNAPSE, , iv., , The neurotransmitter of the synaptic cleft binds with protein receptor molecules on the, postsynaptic membrane. This binding action changes the membrane potential of the, postsynaptic membrane, opening channels in the membrane and allowing sodium ions to, enter the cell. This causes the depolarization and generation of action potential in the postsynaptic membrane. Thus the impulse is transferred to the next neuron., , v., , Having produced a change in the permeability of the postsynaptic membrane the, neurotransmitter is immediately lost from the synaptic cleft. In the case of cholinergic, synapses, acetylcholine (AChE) is hydrolysed by an enzyme acetyl cholinesterase (AChE), which is present in high concentration at the synapse., , vi., , The products of the hydrolysis are acetic acid and choline which are reabsorbed into the, synaptic knob where they are resynthesized into acetylcholine, using energy from ATP., , ******, , 66, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , CHAPTER – 09, , MUSCLE PHYSIOLOGY, , TYPES OF MUSCLES:, There are three principal types of muscles have been observed so far in the animals, which differ in, the animals, which differ in structure (histologically), in location (anatomically) in function, (physiologically) and their manner of innovation (Neurologically). They are as follows;, , Types of muscles, , Morphological types, , Striated Non-striated/Smooth, , Functional types, , Cardiac, , Voluntary, , Involuntary, , PRINCIPAL TYPES OF MUSCLES:, 1. Striated / Skeletal muscles:, a. They are multinucleated., b. Longitudinal and cross striations of alternating light and, dark bands are clearly seen. Hence the name striated, muscles., c. These muscles found in all higher animals and are found, attached to the skeleton of the body and are involved in, skeletal movements. Therefore, they are also referred as, skeletal muscle., d. These muscles are also called as voluntary muscles because their contractile activities, are under the control of central nervous system., e.g., muscles in limbs, tongue, pharynx and beginning of oesophagus., 67, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , 2., , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Non-striated / Smooth muscles:, a. Smooth muscles are fusiform or spindle shaped, with large amount of sarcoplasm., b. The nucleus is oval or round shaped and lies in, the central wide part of the cell., c. The cells are about 15 to 500 lm in length., d. The sarcolemma is thin & less prominent in, smooth muscle fibrils., e. The myofibrils do not show transverse dark and, light striation (bands). Hence smooth muscles are, also called as non-striated muscles., f. They are involuntary muscles. That is, they are not under the control of CNS., g. Smooth muscle occurs in the walls of stomach, intestine, Trachea, Urinary bladder, gall, bladder, ducts of most glands, uterus, vagina, spleen, blood, lymph vessels etc., e.g., posterior part of oesophagus, stomach, intestine, lungs, urinary bladder, blood, vessels, iris of eye and dermis of skin., , 3. Cardiac muscles:, a. These are unique characteristic of heart wall., b. Cardiac muscle cells are uninucleated with, centrally placed nucleus., c. They are cylindrical & branched., d. They are intermediate in condition, i.e. the fibres, resemble both smooth striations with less,, prominent striations., e. Sarcolemma is absent or very thin and indistinct., , 68, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , f. Cardiac muscles cells are much shorter than the skeletal muscles, measuring about 100m, in length., g. The muscle cells are thin branches to form a chain of muscle cells. This joining is, accomplished by means of intercellular junction called intercalated disc., h. This intercalated disc serves as relay striations for the transfer of impulse from one cell to, another., i. Cardiac muscles are capable of strong & rhythmic contraction & do not suffer from, fatigue., j. They are involuntary muscles., e.g., wall of the heart, pulmonary veins and superior vena cava (where these veins enter, the heart), , MUSCLE PROTEINS:, Muscle proteins are contractile proteins and regulating proteins. These proteins constitute about 80%, of the dry weight of muscle. The muscle proteins actin and myosin associated with the contractile, mechanism comprising about 60% of this and remaining 2/5 of muscle protein is shared equally by, protein enzymes and by stroma proteins., , Contractile Proteins:, Myosin:, a. Myosin has a characteristically shaped, molecule like a golf club bat with a, short compact head and a long shaft., b. The length of myosin molecule is, 1500A., , 69, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , c. When myosin molecule is treated with the Proteolytic enzyme trypsin, it separates into two, components, the light meromyosin (LMM) and heavy meromyosin (HMM)., d. The LMM forms the major portion of the tail region. The HMM contributes to the head, (40A in diameter) and neck part of the molecule. The head region is of special functional, significance., e. Schematic diagram of myosin molecule with globular head and long thin tail., f. Light and heavy meromyosin is differentiated on the basis of trypsin digestion which breaks, the myosin molecule into these two parts., g. It carries ATPase enzyme to perform binding activity., Actin:, a. It is a water soluble globular protein and being structurally attached to the Z-line., b. It has a molecular weight of 70,000., c. The actin filaments resemble two strings of beads twisted into a double helix., d. Each head is a molecule of G-actin (Globular-actin) being 55A in diameter., e. Actin protein shows high affinity for calcium ions., f. In the presence of salts & ATP the G-actin molecules polymerise to form F-actin (fibrous –, actin) in the form of long double helix (or) two stranded rope., g. The F-actin double helix has a pitch of about 710A. So that the two strands cross-over each, other once every 355A, , 70, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Regulatory Proteins:, The Troponin and Tropomyosin can regulate the muscle contraction so it is termed as regulatory, proteins., Troponin:, a. Troponin is a globular protein consisting of three sub-units, the calcium binding unit, (Troponin A or C), the inhibitory unit& the tropomyosin –binding unit., b. The three sub units are bound non-covalently to each other the calcium binding unit can, complex with two calcium ions., c. The inhibitory unit saves as regulatory function by binding action F so as to inhibit the, interaction of the actin with myosin., d. The third sub unit of troponin the tropomyosin binding subunit links the troponin, molecule to the F-actin –tropomyosin complex by interacting with tropomyosin., e. Hence, troponin requires two specific sites for its binding with the thin filaments one in the, actin strand and the other in the tropomyosin strand., f. Just as one molecule of tropomyosin spans seven G-actin monomers, one troponin, molecules is attached to every seventh G-actin in the actin, the troponin complex are spaced, out along the action filament at intervals of about 400A., Tropomyosin:, a. This protein constitutes about 3 to 8% of the total protein contents of the muscle filament., b. It has a molecular weight of order of 70,000., c. It is about 400Along and has 20A diameter., d. The amino acid composition reveals the absence of proline and Tryptophan., e. It lacks ATPase activity., f. There are two known forms of tropomyosin - Tropomyosin A and Tropomyosin B., , 71, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , g. Tropomyosin A which is also known as paramyosin can be salted out in dilute ammonium, sulphate solution, while tropomyosin B is water soluble., h. When tropomyosin is mixed with actomyosin it can inhibit calcium activated ATPase., i. It does not inhibit the Mg activated ATPase., , STRUCTURE OF STRIATE/SKELETAL MUSCLE:, , ANATOMICAL ORGANISATION OF SKELETAL MUSCLE FROM GROSS TO MOLECULARLEVEL, (DIAGRAMMATIC REPRESENTATION), , BASIC UNITS OF MUSCLE CELL ORGANIZATION:, 1. Sarcolemma: plasmalemma of muscle cells. External to this cell membrane is a well-developed, , basement membrane., 2. Sarcoplasm - cytoplasm of muscle cells excluding the myofibrils., 3. Sarcoplasmic reticulum - smooth endoplasmic reticulum of muscle cells., 4. Epimysium - thick layer of collagenous connective tissue that separates large bundles of muscle., , 72, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 5. perimysium - collagenous connective tissue that separates smaller bundles of muscle cells called, , fascicles., 6. fascicle - bundle of muscle cells bounded by perimysium., 7. endomysium - thinner layer of connective tissue that separates individual muscle cells., , SKELETAL MUSCLE:, , 1. Connective, , tissue, , in, , the, , form, , of epimysium,, , perimysium, and endomysium surrounds the components of striated muscle as, described above., 2. Skeletal muscle is generally connected to bone via a piece of connective tissue, called a tendon., 3. As mentioned above, individual muscle cells are syncytial (That is to say, each, striated muscle cell contains multiple nuclei (multinucleate)., 4. Each individual muscle cell is called a muscle fiber. Within the sarcoplasm of these, cells are myofibrils composed of repeating sarcomere units. These sarcomeres are, the actual contractile apparatus., 5. The myofibrils are linear arrays of structures known as sarcomeres that are arranged, in an end to end repeating pattern. The sarcomeres contain filaments of actin and, myosin that interact to cause contraction of the muscle cells. See below for sarcomere, structure., , THE BASIC SARCOMERE UNIT OF STRIATED MUSCLE:, , The basic unit of striated muscle, the sarcomere is diagrammed (in Page No. 74). It is, composed of thin actin and thick myosin filaments (as well as a number of other molecules), arranged in an interdigitated linear array., , These molecules form the sarcomere unit, that consists of-, , 73, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , 1. A-band (Anisotropic band) - area containing overlapping actin and myosin filaments, accept in H-band region., 2. H-band - area of myosin filaments where there is no overlap of actin filaments., 3. I-band (Isotropic band) - thin actin filaments + Z-line., 4. Z-line - where actin filaments of adjacent sarcomeres are anchored., 5. M-line - formed by connections between the central portions of adjacent myosin, filaments., , 74, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , MECHANISM OF CONTRACTION OF SKELETAL MUSCLE:, 1., , When the nerve impulse from brain and spinal cord are carried along motor neuron to, muscle fibre Ca++ ions are released in the terminal axon., , 2., , Increases calcium ion concentration stimulates the release of neurotransmitter, (Acetylcholine) in the synaptic cleft., , 3., , The neurotransmitter binds to the receptor on the sarcolemma and depolarization and, generate action potential across muscle fibre for muscle contraction., , 4., , The action potential propagates over entire muscle fibre and move to the adjacent fibres, along transverse tubules., , 5., , The action potential in transverse tubules causes the release of calcium ion from, sarcoplasmic reticulum, which stimulate for muscle contraction., , 6., , The sequences of muscle contraction explained by sliding filament model are as follows:, , SLIDING FILAMENT THEORY:, H.E. Huxley and A. F. Huxley independently proposed the sliding filament theory of muscle, contraction during the year 1954., This theory revolves round the fact that the shortening of sarcomere which results in the, contraction of a muscle fibre relaxes. The overlap between actin and myosin filament is decreased, or reduced., According to this theory, the sliding of the actin filament between the myosin filaments occurs as, a result of attachment, and detachment of the cross bridges present on the myosin filaments with, the actin filaments., , 75, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Steps of muscle contraction:, I. Blocking of myosin head:, i., , Actin and myosin overlaps each other forming cross bridge., , ii., , The cross bridge is active only when myosin head attached like hook to the, actin filament., , iii., , When muscle is at rest, the overlapping of actin filament to the myosin head, is blocked by tropomyosin. The actin myofilament is in OFF position., , II. Release of calcium ion:, i. Nerve impulse causing depolarization and action potential in the, sarcolemma trigger the release of calcium ions., ii. The calcium ion then binds with the troponin complex on the actin, myofilament causing displacement of tropomyosin from its blocking site., iii. As soon as the actin binding site is exposed, myosin makes cross bridge, with actin. The actin myofilament is in ON position., III., , Cross bridge formation:, i. The cross bridge between actin and myosin acts as an enzyme (Myosin, ATPase), which hydrolyses ATP stored in myosin head into ADP and, inorganic phosphate and release energy., ii. This released energy is used for movement of myosin head toward actin, filament., iii. The myosin head tilts and pull actin filament along so that myosin and actin, filament slide each other., iv. The opposite end of actin myofilament within a sarcomere move toward each, other, resulting in muscle contraction., v. After sliding the cross bridge detached and the actin and myosin filament come, back to original position., , 76, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , 77, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , NEURO-MUSCULAR JUNCTION:, Neuromuscular junction (NMJ) is the junction between a motor neuron and a muscle fiber, through, which action potential from the neuron is transmitted to the muscle fiber., The structure of neuromuscular junction can be broadly divided into three parts: Presynaptic,, Synaptic cleft and Postsynaptic portions., Presynaptic Portion:, i., , Motor neurons that have their cell bodies in the anterior horn of spinal cord or brainstem, innervate the skeletal muscle. Motor neuron axons are myelinated and are the largest diameter, axons in the body., , ii., , As the motor neuron axon approaches the skeletal muscle fiber it loses its myelin sheath and, divides into number of fine branches (terminal axons) which end in small swellings (knobs), called terminal buttons, at the centre of muscle fiber in the groove (synaptic trough) but, outside the muscle fiber membrane., , iii., , Each muscle fiber is supplied by one motor neuron terminal. The motor neuron plus the, muscle fiber it innervates is called as motor unit., , iv., , Terminal buttons (synaptic knobs) contains plenty of mitochondria and neurotransmitter, vesicles. The acetylcholine (ACh) is synthesized in mitochondria and stored in vesicles., , v., , The vesicles are clustered around a specific point called active zone, where voltage-gated, Ca++ channels are present and mediate ACh release., , 78, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22

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ZOOLOGY – DSC 1 C, , III SEMESTER / PART-I / ANIMAL PHYSIOLOGY, , Synaptic Cleft:, i., , This is gap between the terminal button and muscle fiber (50-100 nm wide)., , ii., , The basement membrane of muscle fiber in the cleft contains the enzyme acetyl, cholinesterase, which hydrolyzes ACh into acetate and choline., , Postsynaptic Portion (End Plate Membrane):, i., , The muscle fiber plasma membrane that lies directly under terminal axon portion is known as, the end plate membrane (motor end plate)., , ii., , The endplate membrane is thrown into several folds called junctional folds, which contains, nicotinic type of ACh receptors at their crests., , NEURO-MUSCULAR JUNCTION, ******, 79, , LEO ANTHONY, T. / BGS FIRST GRADE COLLEGE, MYSURU-23 / 2021-22