Veterinary Physiology Notes PDF - Mansoura University

Mansoura University Faculty of Veterinary Medicine Physiology Department Notes in Veterinary Physiology Second year – First term By Dr. Nabil Abu-Heakal Dr. Faheim El-Baha...

Mansoura University Faculty of Veterinary Medicine Physiology Department Notes in Veterinary Physiology Second year – First term By Dr. Nabil Abu-Heakal Dr. Faheim El-Bahay Emeritus professor of Physiology professor of Physiology Dr. Youssef El- Seady Professor and head of Physiology Department 1 DIGESTION Introduction The digestive system includes the digestive tract and its associated glands "salivary, pancreas, liver" the tract is extends from the oral opening to the rectal opening, it consists of the mouth, pharynx esophagus, stomach, small intestine and large intestine, it essential for the ingestion and digestion of food (conversion of food into soluble and diffusible substance) through several mechanism: a) Mechanical, as mastication, deglutition "swallowing", regurgitation, rumination, vomiting, gastric, intestinal movement and finally defecation. b) Enzymatic or chemical as salivary, gastric, pancreatic and intestinal enzymes present in secretion of the associated glands. c) Microbiological: through the action of microflora and protozoa present in the ruminant animals. Neurohormonal control of gastrointestinal tract. The autonomic innervation of the mammalian gastrointestinal tract is either parasympathetic or sympathetic. The parasympathetic provide innervation via the vagus nerve to the esophagus, stomach, small intestine and proximal part of large intestine. The sacral segment of the spinal cord provides parasympathetic innervation to the distal portion of the colon, the rectum and the internal anal sphincter. The postganglionic nerve fibers release acetylcholine which is generally considered to be stimulatory to motor (muscular) and secretory activity. But the sympathetic innervation produce inhibition of motility and secretion. Hormonal control of gastrointestinal motility and secretion this includes large number of hormones as gastric, secretin, cholecystokinin - pancreozymin (CCK-PZ), glucagon, enterogastrone, enterocrinin and villikinin. The capacity and length of this tract varies greatly in different animals. In carnivores, it is short and relatively simple whereas in herbivores it is much larger and more complicated. In some herbivores e.g. horse and rabbit, the stomach is relatively simple, but the intestines are very much larger and of greater capacity. 2 The following table show the capacity of the different parts of the digestive tract in gallons. Animal Stomach Small Large Total intestine intestinal capacity Cow 43 gallons 15 80 183 Horse 4 12 30 46 Sheep 5 2 1 8 Pig 2 2 3 7 Functions of GI tract To assist in the acquisition of nutrients. To prepare nutrients for digestion. To digest the nutrients. To felicitate absorption of products of digestion. Absorption of water. As excretory organs to help in elimination of waste products. As an endocrine gland to influence digestion and other metabolic functions. Motility of the GI tract. Mechanical digestion Ingestion or prehension It means the seizing and conveying of food into the mouth. The animal obtain its food by use of a prehensile fore limb (primate, raccoon), snout (elephant) Tongue (cow, ox) or lips (Horse, sheep) highly developed prehensile organs allow a more careful selection of food. The dental arrangement also can be related to diet, and varies from that if the relatively toothless edentates to the presence of large incisors, canines, and molars in carnivores and even more highly specialized molars of herbivores. The sheep has a clefted upper lip, but in goat the upper lip is not clefted. Drinking Is the process by which the fluid is carried to the mouth. In carnivores animals "Dog - cat" the free end of the tongue is like a ladle structure. In other domestic animals this process is made by suction. Through the aid of the tongue "produce negative pressure, while the lips are closed all round except for a small opening under the water. Sucking Is process by which the milk in the teat is forced into the mouth of the suckling animal by creating pressure gradient in the mouth by their tong. 3 The gastrointestinal hormones Gastrointestinal hormones are polypeptides secreted from certain cells of G.I.T mucosa called APUD cells "Amine precursor uptake and decarboxylation:. They are gastric family as gastrin, cholecystokinin and secretin family as secretin, gastric inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), enteroglucagon. Other peptides secreted from G.I.T. and also from brain, includes substance P, neurotensin, bombesin, enkephalin, somatostatin. The most important hormones are shown in the following table. Gastrointestinal hormones Hormone Tissue of Target Action Stimulus origin tissue to secretion 1- Gastrin gastric secretory productio 1- St. of mucosa & cells and n and vagus n. duodenum smooth m. secretion 2. of of HCl. peptides stomach stimulates & proteins gastric in motility stomach. 2- duodenum pancreas, st. food & Secretin mucosa & muscles pancreatic strong upper part of juice acid in of stomach "H2O + standard. jeyunum bicarbonat and small e, inhibit intestine gastric motility. 3- small gallbladde - presence Cholecyst intesitne r- contractio of fatty okinin (upper pancreas n of acids & pancreozy part) gallbladde amino min r acids in (CCk-PZ) - st. the pancreatic 4  juice (rich duodenum in. enzymes) 4- Gastric small gastric inhibit monosacc inhibitory intesitne mucosa gastric harides peptide (upper and secretion and fats in (GIP) part) gastric and duodenum muscles motility stimulates Brunner's glands, stimulate insulin secretion 5- duodenum it is found increase fats in Vasoactiv in GIT & blood duodenum e brain flow, intestinal tissues inhibit peptide gastric (VIP) secretion "HCl" stimulate pancreatic secretion "H2O & bicarbonat e, st. insulin secretion" 6- duodenum jejunum, inhibit carbohydr Enteroglu pancreas motility ate in cogen and duodenum secretion 7- duodenum stomach inhibit fat, and Enterogest both hypertonic erone "all gastric soln. in peptide secretion duodenum inhibit & motility 5  gastric activities" 8- mucosa of inhibit acid in Somatosta GIT. secretion gastric tin hypothala of gastrin, lumen. mus, D- secretin, cells of VTP GIP. pancreas inhibit gastric motility & secretion inhibit pancreatic secretion, gallbladde r contractio n 9- Histamine: - Is present in a high concentration in gastric mucosa. - It stimulates gastric acid secretion "HCl" through it action on H2 receptors in oxyntic cells. - It increase motility & produce vasodilation of GIT. - It action is blocked by some drugs as cimetidine which used in treatment of peptic ulcer. 10- Prostaglandins - It present in gastric mucosa. - Inhibit gastric secretion. - Increase the intestinal motility and secretion. - Produce V.D. of bl. vessels of GIT. Salivary Secretion Saliva is the secretion of major salivary glands, 3 pairs, as parotides, submaxillary and sublingual and also minor salivary gland as buccal, labial and polatine glands. The parotid gland in domestic animal is serous, so secrete watery secretion contain protein but no mucin they secrete enzymes, however in some animals the secretion is devoid of enzymes. But submaxillary and sublingual 6 glands secrete mucous & serous secretion "mixed" the buccal, palatine secrete mucous. The parotid glands secrete continuously, but the flow of saliva varies during the day it increase during feeding and rumination, in cattle parotid gland can secrete 30-50 ml/min during feeding and reduced to 2 ml/min during rest. A- Composition of saliva 1. The amount of saliva secreted per day is about 1.5 litres in human, 42 litres in horse and 100 litres in cow, sheep 8-13 litre. This increase in rumination. 2. The pH of saliva is about 7 in human, 7.5 in horse and 8.6 in ox, cow. 3. It is hypoosmotic relative to plasma, it contain about 99.5% water and 0.5% solids.. Solids includes: a) inorganic substance as bicarbonates, sodium, potassium, chloride, calcium, magnesium, acid phosphate and alkaline phosphate. b) organic substance as digestive enzymes and mucin and non protein nitrogen substance as urea, uric acid. Enzymes of saliva are: - Amylase "ptyallin" is secreted in saliva of man and all animals except (ox - sheep, most birds) but few species of bird e.g. poultry has serous gland and secrete amylase in saliva, but little digestion occur in the mouth. - Other enzymes of saliva; includes: Maltase, lysozsome, catalase, urease enzymes. B- Functions of saliva 1. Saliva moistens the food so facilitates mastication and formation of food bolus to help deglutition also mucin lubricates the swallowing passage and help deglutition. 2. The salivary amylase enzyme "ptyaline" in man and some animals act on cooked starch in the mouth and in the stomach for 15-30 min. amylase Cooked starch → Erthyrodextrin + Maltose Na,Cl Achordextrin + Maltose 2 Maltose 7 3. The lysozyme enzyme has an antiseptic action. 4. Stimulate the taste buds by dissolving the solid food as sugar. 5. It dilutes irritants substance, coals the hot food. 6. It regulate water balance in the body during dehydration through thirst sensation, which is lead to drinking of fluids. 7. The alkaline pH of saliva regulate the rumen pH through neutralization of the excessive acidity produced by fatty acids in rumen. 8. In panting animals as dog it regulate heat by evaporation of saliva during panting. 9. Saliva moistens the buccal mucosa and help speech in human. 10. It washes away the food particles in the mouth so prevent the growth of microorganisms. 11. It excrete some organic substance as urea and some inorganic substance as mercury, lead, iodine and fluoride. 12. Saliva also contain glucagon, somatostatin and some growth factors "its role is unknown in saliva". C- The nerve supply to salivary glands The salivary glands are supplied by both sympathetic and parasympathetic nerves. 1. Sympathetic nerves: Origin from lateral horn cells of the upper 2 thoracic segments of spinal cord and the preganglionic relay in superior cervical ganglia, the postganglionic arise from this ganglia and supply the gland. 2. Effect of sympathetic stimulation: produce little volume, viscous saliva, rich in mucin & enzymes and contraction of myoepithial cells around the salivary acini ", receptors". 2- Parasympathetic nerves The submaxillary & sublingual salivary gland supplied by (chorda tympani) a branch of 7th cranial n. "facial n." origin dorsal nucleus of facial nerve in pons preganglionic n fibre relay in submaxillary & sublingual ganglion, the postganglionic arise from this ganglion to supply the glands. The parotid gland is supplied by a branch of glossopharyngeal n. "9th cranial n." origin from inferior salivary nucleus in M.O. and relay in otic 8 ganglion from which the postganglionic cholinergic fibres arise and supply the glands. Effect of parasympathetic stimulation Produce secretion of large volume "watery" rich in electrolytes, and vasodilation of blood vessels. Fig. :Parasympathetic and sympathetic supply to salivary gland. D- Control of salivary secretion "Regulation" The secretion of saliva is under nervous control through three phases: 1. Cephalic phase i.e. (nervous): this occurs before the food enters the buccal cavity "conditioned reflex". 2. Buccal phase: this occurs when the food enters the buccal cavity "unconditioned reflex" 3. Gastrointestinal phase: This occurs after the food has been swallowed "unconditioned reflex". Conditioned reflex Unconditioned reflex 1. Responsible for 1. Responsible for cephalic phase of salivary Buccal and secretion "Pavlov's gastrointestinal phases of experiment". salivary secretion. 9 2. It is accquired 2. It inherent reflex reflex need intact cerebral "in born" not require cortex and require training or intact cerebral training. cortex. 3. It stimulated by 3. It stimulated by seeing or smelling food, presence of food inside hearing the sounds of food the buccal cavity preparation or thinking incontact with buccal "receptors: visual, mucosa "receptors; taste olfactory and hearing receptors". receptors" 4. Afferent of reflex is 4. Afferent is carried carried to the cerebral via 7th, 9th cranial nerves cortex via visual, to brain stem (directly) to olfactory and auditory stimulate salivary nuclei. nerves. Cerebral cortex centres stimulate salivary nuclei in brain stem. 5. Efferent by 7. Efferent by parasympathetic and parasympathetic and sympathetic n.f.s. to sympathetic n.f.s. to salivary gland stimulate salivary glands. stimulate secretion. secretion. Pavlov's experiment "Conditioned reflex" This experiment is applied on dog with artificial fistula in the parotid duct to collect the saliva. If a dog is allowed to see light, just before feeding and repeated this process several times. Then the light alone without the food can stimulate salivary secretion. This explain that, the light has become an index for food and has been associated into the cerebral cortex with feeding "conditioned stimulus". 10 Fig. : Sham feeding Deglutition or swallowing It is process through which the food pass from the buccal cavity to the stomach. It divided into 3 phases 1. Buccal phase "voluntary". 2. Pharyngeal phase "involuntary". 3. Esophageal phase "involuntary". 1- Buccal phase It is voluntary, it starts after mastication of the food and formation of bolus. The tongue is elevated by contraction of mylohyoid lingual muscles, so the bolus is rolled backward and forced into the pharynx "so the food pass from buccal cavity to the pharynx. 2- Pharyngeal phase It is involuntary phase, it occurs as a results stimulation of pharynx and epiglottis which send afferent impulse to swallowing centres "deglutition centres" in Medulla oblongata from this centre efferent impulse via 5th, 7th, 9th, 10th and 12th crainal nerves produce the following: a) Elevation of the soft palate which prevent food reflux into the nasal cavity. b) Elevation of the larynx against the epiglottis to prevent the food to enter into trachea. c) Deglutition centre send impulse to inhibit respiratory centres during deglutition "Apnoea". d) Rapid peristaltic movement pass from pharynx to the esophagus, the bolus pass into the esophagus. 11 3. Esophageal phase It is involuntary phase, in which peristaltic movements occurs in the esophagus wall to propel the bolus to the stomach. through the relaxated cardia. In animals having an extensive area of esophageal smooth muscle cranial to cardia "Acetylcholine cause caudal esophageal sphincter relaxation which is blocked by atropine. But Epinerphrine produce caudal esophageal contraction. But sheep, ox the striated muscle is predominantly in esophagus so Atropine not affect movements but blocked by d-tubocurarine "neuromuscular blocker". N.B.: Esophagus in sheep, ox and dog has circular and longitudinal striated muscle. But in horse, pig and man the caudal part esophagus and lower third has smooth muscle fibres. Movements of the esophagus 1- Primary peristalsis It occurs during swallowing process, it a continuation of the peristalic movement which begin in the pharynx. 2- Secondary peristalsis It follows the primary peristalsis, to remove any food that remain in the esophagus. They are not preceded by a swallow, it originate in the esophagus as results of distension of esophageal wall by food remnants. 3- Antiperistalsis It occurs in the opposite direction of peristaltic movement in ruminant animals during rumination and eructation. Eructation: Means expell of gases via esophagus by contraction of dorsal ruminal sac, and abdominal muscle. Also relaxation of pharyngeo - esophageal sphincter. 12 Rumination It is process occurs in ruminant animals. At which ruminal content are aspired into the esophagus by pressure gradient without changes in the intraabdominal pressure. Esophageal groove It is a groove extends from the cardia of the stomach of suckling in young ruminants to the abomasum so it is reflexly closed during suckling lead to conduct the swallowed milk directly into the abomasum it is receptors is present in mucous membrane of the lips checks, pharynx and esophagus which stimulate vagus nerve to initiate this reflex and close the esophageal groove. Factors affecting closure of esophageal groove 1. When the calf drank milk, stimulate closure of the groove. 2. The closure of the groove did not occur if milk was given through a tube introduced into cervical esophagus via nasal canal. 3. Local anaesthetization of buccal and pharyngeal mucosa by cocaine, inhibit closure of the groove. 4. Large doses of atropine inhibit the closure of groove. 5. Sodium bicarbonate cause closure of the esophageal groove. Digestion in Simple Stomach Animals Digestion, gastric, pancreatic, bile and intestinal secretion of simple stomach animal as dog, horse and also in man also in abomasum, it is the only part of the ruminant stomach that secrete digestive juices, also pancreatic, bile, intestinal digestive of ruminant animal will discuss in this chapter. 1- Gastric secretion The mucosa of the glandular stomach divided into three regions called cardiac, fundic and pyloric. A) The fundic gland of the stomach "present in fundus" and consists of a) The mucous neck cells: that secrete mucin. b) The chief cells "peptic cells" or zymogen cells: that secrete gastric enzymes as pepsinogen (pepsin), gastric lipase, rennin enzyme "young suckling animals". 13 c) The parietal cells "oxyntic cells": that secrete gastric HCl and intrinsic factor, essential for vit. B12 absorption in the ileum. It also contain carbonic anhydrase enzyme. d) Argentaffin cells: secrete serotonin "5-hydroxytryptamine (5-HT). B) The pyloric gland: In dog it represent 1/2 of stomach in horse 1/3 of stomach and in ruminant 1/3 abomasum. It secrete mucin and Gastrin hormone. Composition of the gastric juice The volume of gastric secretion in human is about 2-3 litre/day and pH is 1-3.5 in adult but 5-6 in infant. Gastric juice is composed of: A) Water 99% B) Solids 1%. The solids are consists of inorganic substance as gastric HCl and organic one as (enzyme pepsin, rennin, gastric lipase, gelatinase lysozyme), Mucin, intrinsic factor. Functions of gastric juice I. Function of gastric enzymes A- Pepsinogen: 1. Pepsin is secreted in inactive form called pepsinogen from peptic cells. 2. It is activated by: Pepsinogen ⎯gastric ⎯⎯⎯ HCl → Pesin (inactive) (active) pep sin Pepsinogen → pepsin autoactivation 3. Pepsin is an active proteolytic enzyme in a highly acidic media of stomach (pH 1-3.5), it has little activity at pH above 5 then become inactive. 4. Pepsin is an endopeptidase, act on protein molecules to produce proteoses, peptones and polypeptides. 5. Secretion of pepsin is stimulated by gastrin, acetylcholine, & histamine. 14 B- Rennin enzyme 1. In some young mammals, including bovine calves and may be infants, the stomach secrete rennin. 2. It an endopeptidase, act on milk to produce milk clots. rennin Ca ++ caseinogen → soluble casein ⎯ ⎯ ⎯→ insoluble calcium pH 6 caseinate "milk clot" 3. The curdled milk "clot" is then digested by proteolytic enzymes, including rennin, pepsin, N.B. Rennin is differ from Renin enzyme secreted from JGA of kidney. Milk clot in human infant is produced by pepsin and HCl. C- Gastric lipase 1. It is of little quantitative importance, it act on butter fat. 2. It has no lipolytic activity on the other fats. D- Gelatinase enzyme Act to liquiefy some of the proteoglycans in meats. II. Functions of mucous secretion in the stomach 1. The mucous cell of pyloric region secrete mucous "viscid" that coats the gastric mucosa with mucous gel layer (1 mm thick). 2. It protect the stomach wall as well as lubricate the food. 3. It form a gastric barrier that prevents digestion of the gastric wall and also reduces the absorption of most substances by gastric mucosa. III. Function of gastric hydrochloric acid "HCl" HCl is secreted by oxyntic (parietal) cells. 1. It activates pepsinogen into pepsin. 2. It provide the acidic pH (1-3.5) which is essential for activity of pepsin during protein digestion. 3. It act on bacteria. 4. It help absorption of iron "ferric ⎯HCl ⎯ ⎯→ ferrous, it also help absorption of calcium. 15 5. It also produce milk curdle, together with pepsin. 6. It regulate the rate of gastric emptying, presence of acid chyme in duodenum delays the gastric emptying. 7. It indirectly stimulate bile flow and pancreatic secretion "through stimulation of CCK and Secretin hormones. Mechanism of HCl formation by paretal cells As shown in the following figure. 1. The intracellular water of parietal cell is dissociates into (H+ and OH-) ions. The H+ions are then secreted into the lumens of the glands by an active transport process in exchange with k. By the activity of H+ - K+ ATPase enzyme. 2. The CO2 produce from metabolic reaction react with water in presence of carbonic anhydrase to form H2CO3 which is dissociated into H+ and HCO3- where the H+ ion react with OH- ions to form H2O but the HCO3- pass to the blood in exchange with Cl- ions. 3. Cl- ions are actively transported to the gastric lumens where they combine with H+ ions to form HCl, by aid of HCO3- ATPase enzyme. 4. The H2O is passively pass into the lumen. 5. The bicarbonate pass to blood combine with Na+ to form NaHCO3 which results in temporal alkalosis "post-prandial alkaline tide". 16 Fig. : HCl formation Control of HCl secretion A) Stimulation of HCl secretion is by secretagogues as: 1- Acetylcholine 2- gastrin, 3- histamine. Histamine act on H2 receptors of histamine to stimulate secretion of HCl. These receptors are blocked by certain drugs e.g. cimetidine which used in treatment of peptic ulcer and hyperchlorhydria "excessive HCl secretion". B) Inhibition of HCl secretion: 1- secretin hormone, 2- CCK, 3- VIP (vasoactive intestinal peptide". C) The relation between HCl and gastrin hormone There is a negative feed back mechanism between the HCl secretion and rate of gastrin hormone, firstly gastrin hormone stimulate HCl secretion but if HCl increase it inhibit the secretion of gastrin (Autoregulatory mechanism of 17 HCl secretion), this is very important to protects gastric mucosa from the harmful effects of excessive HCl secretion Fig. pepsin activation in the stomach Regulation of gastric secretion The gastric secretion is regulated by both nervous and hormonal mechanisms. This divided into 3 phases, the cephalic, the gastric and the intestinal phase. 1- The cephalic phase: This phase is mediated by the brain, the secretion occurs in response to the sight, smell, and or taste of food. This phase is consists of conditioned and unconditioned reflexes". 18  Conditioned reflex Unconditioned reflex 1- Secretion - Before the food - When the food occur enter the mouth present in the mouth before reach the stomach. 2- Receptor - Visual, - Taste buds, auditory and receptor of general olfactory sensation. receptors. 3- Afferent - Optic, - Chorda tympani, auditory, olfactory glosso pharyngeal. nerves 4- Center - Cerebral - M.O. vagus cortex to vagus nucleus. nucleus 5- Efferent - Vagus nerve - Vagus nerve to to stomach stomach. 6- Effect - Stimulate - Stimulate gastric gastric secretion secretion 2- Gastric phase: "hormonal" 1. Once the food enters the stomach, it stimulate the gastrin secretion, which in turn causes secretion of gastric juice. 2. Also local axon reflex in the stomach stimulate gastrin hormone secretion. 3. Vagovagal reflexes that pass all the way to the brain stem and back to the stomach both reflexes cause release of acetylcholine which stimulate oxyntic cells. 4. Also gastrin is stimulated as results of pyloric distension and chemically by polypeptides. N.B. The gastrin release from G cells of pyloric mucosa into the blood and circulate to reach gastric glands in the fundus and body of the stomach to stimulate gastric secretion. 19 3- Intestinal phase 1. The presence of food in the duodenum can stimulate stomach to produce small amount of gastric juice this due to small amount of gastrin are also released by the duodenal mucosa in response to distension or chemical stimuli "meat extract, polypeptides". 2. But the presence of fat, excess acid, hypertonic solution in duodenum inhibits gastric secretion and motility due to GIP "enterogastrone H.". Gastric Motility Gastric motility or mevements of stomach. A- Movements of empty stomach 1- Tonus rhythm a- There are regular weak contraction of about. 2-4/minute. They pass from the body of stomach to pylorus. b- They depend on local nerve plexus. 2- Hunger contractions a- These are strong gastric contractions, that occurs during fasting. b- When the stomach is emptied, mild peristalic contraction begin, then gradually increased about 60 minutes, these contraction called hunger contraction "mild painful" and are associated with sensation of hunger. This sensation is not caused by the hunger contraction. Mechanism of hunger a- In the hypothalamus there is appestate centre or (satiety centre and feeding centre). b- When blood glucose level is increased. The satiety centre is stimulated, which in turn inhibits the feeding centre. So there is no desire to eat "not hungry". c- But in fasting, the hypoglycaemia "decrease blood glucose level" the effect of satiety centre on feeding centre is released. So the feeding centre is activated and cause the sensation of hunger, at the same time it stimulate vagus nucleus in M.O. → vagus → stimulate gastric contraction "Hunger contractions. N.B.: Vagotomy will abolish the hunger contractions but not the hunger sensation. 20 B- Movement of filled stomach 1- Receptive relaxation: When food enters the stomach, gastric muscles is relaxed which is initiated by the movement of the pharynx and esophagus through vagovagal inhibitory reflex, when the stomach is distened by food entrance lead to further relaxation. 2- Peristaltic movements a- They occur when the stomach, become distented with food. They consists of waves of contractions preceeded by waves of relaxation in the stomach wall. b- They move from fundus to pylorus but it marked increased in pylorus, it spontaneously starts in the mid point of greater curvature of stomach. c- It increased by vagus and gastrin but decreased by sympathetic stimulation and secretin hormone. d- It is very important for mix food with gastric juice, digestion of food particles. e- Evacution of liquified gastric content into the duodenum. 3- Antiperistaltic movemnts. a- They occur in opposite to peristaltic contraction or from pylorus to fundus. b- They return the solid and semisolid particles of food from pylorus to fundus. Factors affecting emptying of stomach 1- Nervous factors a- Vagal stimulation: help emptying of stomach "motor to gastric wall and inhibitory to pyloric sphincter". b- Sympathetic stimulation: delay emptying of stomach "inhibit gastric motility and motor to pyloric sphincter". 2- Chemical factors a- Cholinergic drugs, coffee, NaHCO3 increase gastric motility. b- Adrenergic drugs, atopine, bacterial toxin decrease gastric motility. 21 3- Distension of stomach, slight distension stimulate gastric motility but sever distension inhibit it. 4- Intestinal content a- Presence of HCl, protein, hypertonic solution in the duodenum and duodenal distension lead to reflex inhibition of gastric motility "Enterogastric reflex" which is important to gives enough time for protein digestion in the stomach and for HCl to neutralize by pancreatic juice. b- Fat stimulate enterogastrone hormone so inhibit gastric motility. Vomiting It is the evacuation of gastric contents through the esophagus, pharynx and mouth. It is often starts with salivation, sensation of nausea. Mechanism of vomiting 1. A strong contraction appears at incisura separating the body from the pylorus. 2. The body of the stomach and the cardia are completely relaxed "passive". 3. A strong contraction of the diaphragm, abdominal muscles, plevic muscles, so marked increase in intraabdominal pressure that squeezing of relaxed stomach and expulsion of its contents into the mouth. 4. During vomiting, the posterior nasal opening is closed by elevation of soft palete, the respiratory passage is closed by elevation of larynx to be covered by epiglottis and inhibition of respiration. 22 Causes of vomiting A) Reflex vomiting: as result of stimulation of vomiting centre in medulla by afferent impulse from different parts of the body. a) Conditioned reflex "emotional cause". b) Mechanical stimulation of root of the tongue, soft palate or pharynx. c) Chemical irritant in contact with gastric mucosa "toxic substance". d) Intestinal, renal, biliary colic. e) Sea sickness "stimulation of labyrinth. Fig. Vomiting reflex B- Central vomiting The vomiting centre is stimulated via chemoreceptor trigger zone due to: a) Drugs as apomorphine., b) Meningitis., c) Hypoxia as in high altitude., d) Morning sickness in pregnant woman due to acidosis. 23 Vomiting in animals 1. In horse. The stomach are located centrally in the abdominal cavity so it is far away from the effect of contraction of the abdominal muscles. So vomiting in horse is give a bad indication about stomach it indicate perferation of stomach. 2. In rat the cardia of the stomach can not be fully open and initiation of vomiting leads to perforation of the stomach and leads to pertionitis and death. 3. In ruminant animals the vomiting centre is abscent. 4. In dog and cat, vomiting is very essential process because the mother can feed its newly born through feeding and digest the food then vomit it. Peptic ulcer It is an excoriated area of the mucosa caused by digestive action of gastric juice, it may be gastric or duodenal ulcer. Basic cause of peptic ulceration Imbalance between the rate of gastric juice secretion and the degree of protection of the gastro duodenual barrier and neutralization of gastric acid by duodenal juices. Therefore: 1. Excess secretion of acid and pepsin by gastric mucosa. 2. Diminished capability of the gastroduodenal mucosal barrier to protect against the digestive properties of the acid-pepsin complex. About 85% of patients with duodenal ulcer are caused by excessive secretion of acid and pepsin by gastric mucosa, while 15% patient is due to decrease mucous secretion, less than normal protective value and failure of normal duodenal gastric feedback mechanisms to limit the rate of gastric emptying into duodenum or failure of pancreatic and bile secretion to neutralized gastric juice that enter duodenum. 3. The development of duodenal peptic ulcer is strongly hereditary. 4. Other factors: Psychogenic factors, also ingestion of aspirin or alcohol, reflux of duodenal content into the stomach leads to gastric ulceration due to bile acids "detergent effect" so reduce mucosal resistance. 24 * Experimental peptic ulcer in dog and other animals Peptic ulcer is created in dogs by the following: 1. Feeding ground glass which causes excoriation of pyloric wall, and allow the peptic juice to digest the deep layer of mucosa. 2. Repeated injection of histamine causes excessive secretion of gastric juice. 3. Obstruction of gastric & duodenal blood flow. 4. Continual infusion of HCl through stomach tube. 5. Transplantation if the pancreatic duct to the ileum. Treatment of peptic ulcer 1- Medical treatment a) Removal of stressful that lead to excessive acid secretion. b) Antacid drugs. c) Administration of the drug that block (H2 receptors) of histamine e.g. cimetidine "drug". d) Removal of such ulcer causing factors as aspirin alcohol. 2- Surgical treatment 1. Removal of pyloric antrum "to remove the effect of gastrin". 2. Highly selective vagotomy "section of vagal fibre that supply fundus & body of the stomach. Achylia gastrica Complete atrophy of gastric mucosa, characterized by absence of HCl, lack of intrinsic factor lead to pernicious anaemia, and weak bone development. Achlorhydria, means stomach fails to secrete HCl. 25 Pancreatic juice The pancrease is considered as an endocrine gland secrete insulin hormone from beta cells, glucagon from alpha cells and somatostatin from data cells of islets of Langerhans and exocrine gland, secrete pancreatic juice into pancreatic duct "digestive functions" the pancreatic duct units with the common bile duct to form a common duct that open in the duodenum through the sphincter of Oddi. Characteristics of pancreatic juice 1. Pancreatic juice contains enzymes for digesting all three major types of food (proteins, carbohydrates and fats). 2. It also contains large quantities of bicarbonate ions which play an important role in neutralization of acid chyme emptied by the stomach into the duodenum. 3. pH alkaline 7.8-8.4, volume about 1-2 litre/day. Functions of pancreatic juice I. The proteolytic enzymes They are trypsin, chymotrypsin, carboxypolypeptidase, ribonuclease and deoxyribonuclease. a- Trypsin and Chymotrypsin 1. Act on protein and digest it into peptides of various size but do not cause release of individual amino acid. 2. They secreted in the inactive forms from pancreatic cells "trypsinogen and chymotrypsinogen and activated in the intestinal tract as following: 26  Enterokinase a- Trypsinogen → trypsin enzyme tryp sin b- Trypsinogen → trypsin autoactivation c- Chymotrypsinogen ⎯trypsin ⎯⎯→ chymotrypsin d- Autoactivation "chymotrypsinogen → chymotrypsin N.B.- Enterokinase enzyme is secreted from intestinal mucosa, when acid chyme comes in contact with intestinal mucosa. It activate trypsinogen. b- Carboxypolypeptidase 1. It is secreted in the intactive form procarboypolypeptidase by trypsin enzyme and by autoactivation. 2. It is splits individual aminoacids from the carboxyl ends of the peptides "exopeptidase", thus completing the digestion of protein into amino acids. c- The nucleases enzymes (ribonuclease, deoxyribonuclease) act on nucleic acids "ribonucleic & deoxyribonucleic acids. II. The digestive enzyme for carbohydrates Pancreatic amylase Which hydrolyzes starches, glycogen and most of carbohydrates except cellulose to form disaccharides and a few trisaccharides. III. The main enzymes for fat digestion 1- Pancreatic lipase Which is capable of hydrolyzing neural fat into fatty acids and monoglycerides. 2- Cholesterol esterase Which cause hydrolysis of cholesterol esters. 3- Phospholipase Which splits fatty acids from phospholipids. N.B.: Trypsin inhibitor 1. It is important that the proteolytic enzymes of the pancreatic juice not became activated until they have been secreted into the intestine. 27 2. Trypsin inhibitor prevent the activity of trypsin and prevent the digestion of pancreas by its digestive enzymes. 3. If pancreatic ducts are block the amount of enzymes increased and damaged the pancreas "acute pancreatitis". IV. Secretion of bicarbonate ions 1. Bicarbonate ions and water are secreted from the ductules of the pancreatic glands, it is very important to neutralyze the acidity of the gastric juice in the duodenum. 2. It provides the optimal pH for action of pancreatic enzymes. The cellular mechanism for secreting sodium bicarbonate (NaHCO3) solution into pancreatic ductules is illustrated in the following figure. Regulation of pancreatic secretion It regulated by both nervous and hormonal mechanisms but the hormonal is the more important: I. Nervous regulation When the cephalic "conditioned & unconditioned relfexes" and gastric phases of the stomach secretion occurs the parasympathetic impulses are transmitted via vagus to the pancreas results in secretion of pancreatic juice "small volume of H2O and bicarbonate, but rich in enzymes". But sympathetic "decrease pancreatic secretion specially. Bicarbonate due to stimulation of  adrenergic receptors. II. Hormonal regulation After acid chyme enters the small intestine, pancreatic secretion become Copious "increase volume" due to stimulation of Secretin hormone also cholecystokinin cause secretion of enzymes. Secretin hormone Cholecystokinin pancreozymin CCk-PZ Nature - a polypeptide "27 - a amino acids polypeptide "33 amino aicds" 28 Secretion - Secreted - from upper from S cells in part of small mucosa of intestine duodenum and "duodenum, upper jejunum jejunum" Stimulated - presence of - presence of by acid chyme in the proteases and duodenum peptones and long chain fatty acid in the duodenum. Effects 1- St. pancreatic 1- St. pancratic secretion large secretion large volume "rich in volume "rich in bicarbonate upto digestive enzymes. 195 mEq./Litre and water" little enzymes. 2- it neutralize the 2- it has acid chyme by enterogastorne like NaHCO3 effect, decrease gastric motility and HCl+NaHCO secretion 3→NaCl+H2CO3 N.B.:: (Nicotine) inhibit release of secretin hormone, so reduce NaHCO3 secretion. high incidence of duodenal ulcer in cigarette smokers. 3- secretin inhibit gastric motility and secretion 29  4- stimulate intestinal motility and secretion Bile Secretion All the hepatic cells secrete bile into minute bile canaliculi, then into terminal bile ducts to hepatic duct and common bile duct from which the bile either empties directly into the duodenum or into cystic duct into gallbladder. The gall bladder bile The bile secreted continually from liver cells is normally stored in the gall bladder until needed in the duodenum, the total secretion of bile 1-2 litre/day it is concentrated in gallbladder to "100 ml" and pH become acidic 6 due to reabsorption of NaHCO3.but the liver bile is alkaline pH 7.8. Gall bladder are abscent in the following animal horse, donkey, camel, deer, rat and pigeon. But present in cattle, sheep, dog, cat, mouse, fish, and birds. The concentration of bile in gall bladder is occur (5-10 times) in man and following animals dog-cat. rabbit, mouse, chicken but not by cow, sheep, goat and pig. Evacuation of gall bladder bile 30  The basic conditions necessary for evacuation "emptying" of gall bladder are: 1. The sphincter of Oddi: must relax to allow the bile to flow from the common bile duct to the duodenum. 2. The gallbladder wall must contract to provide the force required to move the bile into the common duct. Factors control the evacuation 1- Hormonal factor "Cholecystokinin" It secreted in responses to presence of fat in small intestine, into blood and passing to gallbladder causes specific contraction of the gall bladder muscle. 2- Parasympathetic effect Vagal stimulation associated with cephalic phase of gastric secretion leads to weak contraction of the gall bladder. 3- Neurogenic or myogenic reflex from gall bladder to sphincter of Oddi "relaxation of sphincter, when the gall bladder contracts". Functions of the gall bladder 1. Storage if bile : between meals the bile flows to cystic duct to be stored in the gallbladder. 2. Concentration of liver bile: as result of active reabsorption of Na+ ions and passive reabsorption of Cl- & HCO3, and H2O. 3. Acidification of bile: the liver bile pH is 7.8-8.6 it become acidic pH 6-7, so prevents Ca++ ion precipitation, help in prevent gallstones. 4. Secretion of mucous "white biles" from mucous glands of the gallbladder mucosa, this mucous protect the mucosa and act as a lubricant in the intestine. 5. Evacuation of bile. Choleretics They are substance that increase bile secretion by liver e.g. 1. Bile salts, secretin, and gastrin hormones. 2. Choleretic drugs as acetylcholine which induce vasodilation, so increase hepatic blood flow. 31  The bile salts is the most potent choleretics, it act through (enteroheptic circulation): about 94% of bile salts are reabsorbed by active process through the intestinal mucosa of ileum, then enter the portal circulation to the liver then resecrete into the bile. Cholagogues They are substances that cause contraction of the gallbladder, and increase the bile flow into the duodenum e.g. a) Cholecystokinin hormone. b) Cholinergic drugs "but weak effect" e.g. "Acetylcholine". c) Magnesium sulphate. Composition of bile The following table gives the composition of bile "liver bile and gallbladder bile". The bile consists of secretory product "bile salts" and excretory product "bile pigments". Composition Liver bile Gallbladder bile Water 97.5 gm% 92 gm% Bile salts 1.1 gm% 6 gm% bile pigments 0.04 gm% 0.3 gm% cholesterol 0.1 gm% 0.3-0.9 gm% fatty acids 0.12 gm% 0.3-1.2 gm% lecilthin 0.04 gm% 0.3 gm% sodium 145 mEq/L 130 mEq/L potassium 5 mEq/L 12 mEq/L bicarbonate 28 mEq/L 10 mEq/L calcium 5 Eq./L 23 mEq/L chloride 100 mEq/L 25 mEq/L The bile salts and their functions The bile salts secreted by liver cells per day is about 0.5 gm. Its precursor is cholesterol, then converted into cholic acid or chenodeoxycholic acid, which are combined with glycine or taurine to form (glycocholic & taurocholic acids) and form Na and K salts of these acids to secrete in the bile. The bile salts has an important functions in fat digestion. 32 Functions of bile salts 1. They have a detergent action on the fat particles in the food, decreases the surface tension of the particles and allows breakdown of fat particles into minute size. "Emulsifying or detergent action". 2. Bile salts help in the absorption of fatty acids, monoglycerides, cholesterol and other lipids from the intestinal tract, through forming minute complexes with these lipids "micelles" which are highly soluble. 3. Help in absorption of fat soluble vitamines vitamins A,D,E and K. Deficiency of vit. K is due to cease bile secretion, which result in deficient of blood coagulation factors "prothrombin or II, and factors VII, IX and X. 4. Choleretic action of bile salts, it stimulate liver cells to secrete bile. 6. Solvent action: when the bile become concentrated in the gallbladder the bile salts and lecithin become concentrated along with the cholesterol, which keeps the cholesterol in solution, so prevent precipitation of cholesterol which may results in formation of gallstones. N.B. causes of gallstones a- Too much absorption of H2O from bile. b- Too much absorption of bile acids from bile. c- Too much cholesterol in bile. d- Inflammation of the gallbladder epithelium. N.B. the normal ratio between choelsterol and bile salts in bile is about 1:26. If this ratio decrease to 1:13 the choelsterol will precipitate and form gallstones. 6. Bile salts stimualte intestinal movements, so they used as laxatives due to stimulation of peristaltic movement. Bile pigments They are the end products of haemoglobin metabolism originated from destruction of old erythrocytes as discuss in blood. They are biliverdin, "green pigments" and bilirubin yellow pigment". In the blood it is called haemobilirubin or protein bound bilirubin "unconjugated" and then conjugated with glucuronic acid to form cholebilirubin "conjugated bilirubin "soluble" secreted from liver. Bile pigments excreted in urine as urobilinogen and in feces as sterobilinogen. 33 Jaundice "Iectrus" It is the yellow colouration of skin and mucous membrane and sclera due to increase bilirubin in blood. The total bilirubin "conjugated and unconjugated" concentration in the serum is normally 0.2-0.8 mg%, Jaundice occurs when the level rises above 2 mg%. 34 The following table illustrate the cause and types of Jaundice. Haemolytic Obstructive Hepato Jaundice or choelstatic cellular Jaundice 1- Cause haemolytic extra hepatic damaged of anaemia obstruction liver cells eryth- of bile ducts "virus roblastosis "gallstone" hepatitis, fetalis intrahepatic toxic drugs. bacterial "virus toxin, some hepatitis". drugs 2- Blood increase increase increase both haemo- chole- haemobilirub bilirubin bilirubin in & cholebilirubi n 3- Urine no bilirubin dark in darker in colour colour 4- Stool darker than very pale paler than normal normal 5- Liver normal impaired depressed function 6- Digestion normal marked digestive digestion digestive disturbance disturbance 7- Van Den is indirect is direct is biphasic Bergh purple colour purple colour direct & reaction appear after appear after indirect light adding adding purple (Serum + Erlich's Erlich's colour Erlich's reagent then reagent only become reagent). alcohol darker by adding alcohol 35 The Small Intestine Functions of Small Intestine I. Digestion (Intestinal secretion) Volume 1-1.5 litre/day. Three kinds of secretion are formed by intestinal mucosa. I. An alkaline fluid secreted from the crypts of Lieberkuhn "intestinal juice or succus entericus, pH 7.5-8.3. It is isotonic fluid contain, NaHCO3, NaCl and two enzymes, Enterokinase , and traces of amylase 2. Mucous secretion from goblet cells which Lubricates epith. surface and protect mucosa from chemical damage by the acid chyme. 3. Sloughed mucosa: "desquamated mucosal cells" which contain many digestive enzymes. The intestinal enzymes 1-peptidases a- Aminopeptidase : act on polypeptides at the free amine end polypeptides ----------→ peptides & free a.a. b. Dipeptidase act on dipeptides → 2 amino acid Digestion of carbohydrate 36 2- Disaccharidases: group of enzyme act on disaccharides → convented into mono saccharides They includes a) Maltase act on Maltose → 2 glucose b) Lactase lactose → glucose + galactose c) Sucrase or invertase act on Sucrose → glucose & fructose 3. Intestinal amylase : complete action of salivary & pancreatic.amylase on carbohydrate digestion 4. Intestinal lipase neutral fat → fatty acid glycerols 5. Intestinal nucleases a) Poly nucleotidase Nucleic acid → nucleotides b) Nucleosidases Purine or pyrimidine nucleosides → purine & pyrimidine bases & pentose phosphate 6. Phosphatase : remove phosphate from certain organic phosphates Regulation "control of intestinal secretion" 1 Local axon reflexes Presence of food in the intestine result in distension of the intestine → local stimulation through local axon reflex produce intestinal secretion. 2. Nervous regulation - Vagus stimulation induce increases secretion - Sympathetic st. decrease intestinal secretion of Brunners glands 3. Hormonal regulation Secretin, CCk, and Enterocrnin they stimulate intestinal secretion, Catecholamines inhibit intestinal secretion 37  Prostaglandins, VIP secreted intestinal mucosa stimualte intestinal secretion II. The absorption It is the passage of digested food from the small intestine lumen through the mucosal cells into the blood stream. Routes of absorption Absorption occurs through the villi which contain blood capillaries and central lacteals. 1- Blood capillaries Receive water, minerals, vitamins, monosaccharides 30% of fat to portal vein to liver then general circulation. 2- Central lacteals Receive about 70% of fat to thoracic duct, to venous blood to the general circulation. Absorption occurs by different mechanisms depending on the nature of the absorbed substance. a- (diffusion, faciliated diffusion, active transport and endocytosis). All parts of the gastrointestinal tract are capable of absorption "water, glucose, alcohol, but the small intestine is the main site of absorption because of its length and presence of villi and microvilli and rich blood and lymph supply. Factors affecting absorption 1. Physico-chemical factors: a- The concentration gradient: Absorption of some substance by passive diffusion is increased when its concentration inside the intestinal lumen exceeds more than its level or concentration in the blood. b- Osmotic pressure: The presence of hypertonic solution in the intestinal lumen decreases the rate of absorption. c- The intraintestinal pressure The absorption increases with the increase in the intraintestinal pressure. 38 d- The solubility of the substance The high soluble substance is the more absorbed - HCl, increase the calcium solubility, so help in calcium absorption. - Bile salts help the absorption of fatty acids. 2. Intestinal movements Segmentation, and peristaltic movements and movements of villi promote the absorption through increasing intraintestinal pressure & blood and lymph flow. 3. Blood and lymph flow Lymph flow is necessary for fat absorption 4. Vitality of the intestinal mucosa, it depends on blood supply, oxygen supply and also vit B compelx. 5. Hormones a- Thyroid hormones secreted from thyroid gland, glucocorticoids from adrenal cortex, helps absorption in general. b- Parathyroid hormone secreted from parathyroid gland help absorption of calcium and phosphorus. 6. Duration of contact of food with the intestinal mucosa. In diarrhea the duration is decrease so the absorption rate is reduced. Digestion and absorption in GIT Absorption of carbohydrate Monosaccharides "glucose, galatose, fructose, mannose, xylose, arabinose are end products of carbohydrate digestion. Mechanism of glucose & galactose absorption The glucose absorption is an active transport, that depends on, sodium ions in intestinal lumen. Sodium Co transport or secondary active transport of glucose 1. There are carrier protein for transport of glucose and galatose present in the brush border of the epithelial cells. 2. This carrier protein has receptor sites for both glucose and sodium ions. So the carrier will not transport glucose in the absence of sodium. 39 3. The energy to cause movement of carrier from the exterior of the membrane to the interior is derived from the difference in sodium concentration between the outside and inside, so that when sodium diffuses to inside the cells it drags the glucose along with it. 4. However, this increases the intracellular glucose concentration to a higher than normal level, then glucose diffuses by "facilitated diffusion" through basolateral membrane of the epithelial cells into the extracellular fluid then to capillaries. 5. The sodium is pumped outside the cells by Na-K ATPase. N.B. If sodium absorption is inhibited, the glucose absorption is decrease. N.B. Fractose is absorbed by passive facilitated diffusion process. Digestion of protein in GIT pepsin → proteases, peptones, polypeptides Pr oteins A ( stomach pH 2 - 3) Trypsin (pancrease)→ Chymotrypsin carboxypolypeptidase peptidase → Polypeptides + aminoacid Aminoacids A (int estine ) (aminopeptidase dipeptidase) Absorption of protein The amino acid absorption has 4 different carrier systems transport a- neutral amino acids carrier, b- basic amino acids carrier, c- acidic amino acids carrier, d- two amino acid proline and hydroxyproline carrier. It is like absorption of glucose i.e. sodium cotransport mechanisms "depends on sodium transport". L-aminoacids absorption i.e. an active transport, but D-amino acids are absorbed by passive diffusion. 40 Digestion of fat in GIT bile salts Fat → Emulsified fat (int estine ) neutral fat Bpancreatic lipase triglycerides fatty acids and 2 - monoglycerides small amount short chain triglycerides "butter fat" is digested in stomach by gastric lipase Absorption of fats 1. Hydrolysis of triglyceride results in formation of 2 monoglycerides and fatty acids with a little glycerol. These products are not water soluble but in the presence of bile salts they are solubolized by the formation of "micelles" "5 nm in diameter". 2. They diffuse between the villi and simply diffuse to the interior of the cells. 3. The fat fragments "fatty acids, monoglycerides" are taken by the smooth endoplasmic reticulum to form triglycerides, and converted to B- lipoprotein in the Golgi apparatus and release as chylomicrons and very low density lipoprotein (VLDL) into the spaces between cells to the lymph in the central lacteal of the villi to reach the blood via the thoracic duct. 4. Short, medium chain fatty acids diffuse directly into the portal blood across the epithelial cells of villi because of it more water soluble. Absorption of vitamins Fat soluble vitamins (A,D,E,K) are absorbed with fat, but water soluble vitamins are: a) Simple diffusion e.g. vit. C, biotin and , niacin. b) Facilitated diffusion e.g. vit. B2. c) Active transport e.g.. vit. B12 & folic acid 41 Large intestine Functions of large intestine I. Water and electrolytes absorption 1. Water passes freely in both directions across the epithelial cells of both small and large intestine but more water absorption occur in large intestine. 2. Sodium is absorbed by an active transport process. 3. In distal part of small intestine and mucusa of large intestine actively secretes bicarbonate ions while it simultaneously actively absorbs an equal amount of chloride ions in an exchange transport process. 4. The absorption of sodium & chloride ions creates an osmotic gradient across the large intestine mucosa which in turn causes absorption of water. II. Secretion Large intestine secrete mucin which bind the fecal particles and lubricate the passage of feces. III. Digestion: only in herbivores where cellulose digestion is carried out by intestinal microflora Bacterial action in the colon. Numerous bacteria e.g. colon bacilli" are capable to synthesis vitamins in the colon as vit. K, Vit. B. complex and some gases as CO2, hydrogen, and methane. N.B. Cellulose is not digested in human Movements of intestine "intestinal motility" Movements of small intestine The movements of small intestine are essential for mixing the digestive enzymes with ingesta, and help absorption and movements of food inside the intestine and expel the residue to the large intestine. Types of movements 1- Peristaltic movements: a propulsive movements" It is a wave of contraction preceded by a wave of relaxation it occurs by a local axon reflex through local Aurbach's plexus, so it is neurogenic in nature, so they still occur after cutting of extrinsic nerves of the intestine. It stimulated 42 by distension of intestinal wall results in stimulation of mechano receptors, the impulse pass to local plexus. "Myenteric reflex". which produce deep contraction of the circular muscle behind the point of stimulation "cholinergic fibres " and relaxation in front of it "purinergic fibres" - Significance of peristaltic movements a) It propagates intestinal content towards the colon. b) It help digestion, through mixing the food with digestive enzymes. c) It help absorption through increase blood, lymph flow, and intraintestinal, pressure. 2- Antiperistalsis It is a peristalsis in the opposite direction it occurs normal at duodenum to help mixing of the acid chyme with the alkaline duodenal content or at lower end of ileum, to prevent rapid evacuation of intestinal content. 3- Segmentation movements "Mixing contractions" a) They are myogenic in nature not depends on auerbach's plexus. b) They consists of several constrictions appear at the same time and divide the intestine into equal segments, after sometime each segment is constricted in the middle while the previous constriction disappears. Significance 1. They help digestion through mixing the food with the digestive enzymes "so it called " mixing contraction". 2. They help absorption, through help blood and lymph supply and increases intraintestinal pressure and time of contact of food with mucosa.. 4- Movements of villi: It is stimulated by "villi kinin". a) Pumping movements "lengthening and shortening" when the villi elongates it absorbs the intestinal content, but when they shorten, it pumps its content into the blood. b) Side to side movements this help digestion by mixing the food with the digestive enzymes and also absorption 43 Movements of the large intestine I. Motility of the colon 1. Rhythmic segmentation contractions They are myogenic in nature, it help absorption of water & electrolytes. 2. Peristalsis movements. a- It is a weak peristaltic movements, which propel the colonic contents toward the rectum, also it allow the colon to store its contents for long time, and help absorption of water & electrolytes. 3. Antiperistalsis movements weak antiperistaltic movements occur in the colon, to regurge its contents. 4. Mass peristaltic movements This occurs only in colon and consists of simultaneous contraction of its smooth muscle over large area, results in movement of content from one portion of the colon to another. II. Movement in the caecum The movements of the caecum are peristaltic & antiperistaltic "weak movements". The caecum in non ruminant animal as horse, rabbit is large size act as site for cellulose digestion 44 Defecation Defecation is a reflex act in which the feces are discharged from the terminal colon and rectum "it is spinal reflex". It is subject to voluntary inhibition in trained animals and human. The efferent pathways of the defecation reflex are cholinergic, "Thus the parasympathomimetic drugs make the reflex more vigorous. The distension of the terminal colon and rectum stimulate the mechanoreceptor in its wall, which discharge impulse via pelvic nerve to defecation centre, results in, strong peristaltic movement of the colon , contraction of the longitudinal muscle of the rectum and relaxation of the internal and external anal sphincters. The defection centre present in secral region. This reflex is involuntary "autonomic reflex in infant" but in adult, it is voluntary reflex "in human". It also by facilitation of the reflex by centres in the brain. In humans, spinal damaged above the lumbosacral regioin results in transient incontinence. The reflex soon returns and autonomic evacuation follows mass movement in the proximal colon. 45  Ruminant Digestion The principal feature of the ruminant digestive system is that fermentative digestion due to bacteria and protozoa occurs in the stomach "the rumen and the reticulum" but the hydrolytic digestion due to digestive juice of the abomasum and intestine. The suborder Ruminantia does not includes all animals that ruminate, it includes cattle Buffalo, ox sheep, goat, deer, girafte, gazelle etc. The suborder Tylopoda, includes, Camel, dromedary Ilama. The camel can ruminante. The stomach of Tylopoela is similar to that of ruminant except the omasum is abscent "vestigial" and the areas of cardiac glands open into the ventral sacculated surfaces of the rumen and reticulum that form the so called (water cells). The fermentation is also occurs in large intestine "caecum of the horse. The Rumen & reticulum The contents of the rumen and reticulum in fully feed adult cattle is about 30-60 kg, but in sheep is about 4-6 kg. 1. The fermentation process occurs in rumen & reticulum after the food enters for about 8 hours/day. 2. The bacteria and protozoa of the rumen live on the food and cause extensive chemical changes, the soluble products of fermentation are largely absorbed, and the mateiral leaving the rumen represents "mixture of food residues, bacteria, protozoa and some soluble fermentation products. Fig. Cattle stomach 46 Honeycomb” interior lining of the reticulum Interior lining of the rumen, revealing papillae Functions of rumen & reticulum I. Fermentation of carbohydrates a) The soluble sugars are rapidly fermented and the starch are less rapidly fermented, but cellulose and hemicellulose are slowly fermented. b) The results of the carbohydrate fermentation are simple mixtures of volatile fatty acid (VFA) and CO2, VFA are acetate, propionate and butyrate in the following percent respectively, 60-70%, 15-20%, and 10-15%. c) Also lactic acid is found in the rumen when the animals are fed on root crops containing large quantity of soluble sugar or in high starch diets. The lactate may be fermented to acetic and proponic acids, so it is an intermediate product. II. Gas production a) The gas mixture in the rumen are carbon dioxide and methane and some nitrogen and traces oxygen. b) The methane is formed by the reduction of CO2 by methanogenic bacteria. c) The feeding is followed by an increase of gas evolution. III. Protein digestion a) The digestion of protien in rumen, start with hydrolysis. b) The nitrogen containing compounds are fermented by bacteria in the rumen and reticulum results in production of ammonia, carbon dioxide. c) The ammonia is used by the bacteira for formation of amino acids and microbial proteins. 47  The excess ammonia is absorbed from the rumen to reach the liver for urea formation. d) The microbial protein is used by the animal either by autolysis or by digestion in the abomasum. Protein digestion in the ruminant 48  Fig.. Nitrogenous cycle in Rumen. IV. Lipid hydrolysis a) The triglycerides undergo hydrolysis in the rumen to glycerol and fatty acids, it occurs by rumen microorgnaism. b) The glycerol is fermented into propionic acids & succinic and lactic acids. c) Phospholipids are similarly hydrolyzed. V. Synthesis of vitamins a) Synthesis of vitamins B complex. It is impossible to produce in adult ruminants the characteirstic signs of deficiencies of any the members of vit. B complex. but it may occurs in young ruminants before the bacteiral flora of the rumen have developed. The only established vit. B deficiency of adult 49 ruminants is due to cobalt defieicney in diet, which is essential for synthesis of vit. B12 in rumen by ruminal bacteria. b) Vit. K also is synthesized in rumen. VI. Cellulose digestion 1. The cellulose is the main constituents of crude fibres of plants. The cellulose is digested by microbial enzyme "cellulose" producing (VFA) volatile fatty acid: and CO2 methane and ammonia. 2. The fatty acids are absorped from the ruminal wall to the blood to the liver. acetic acid is oxidized to give energy used in metabolism. The propionic acid is converted to glucose and stored as glycogen, butyric acid and acetic acids are most important sources of milk fat in lactating animals. 3. Gases are expelled by eructation, but little amounts of gases are reabsorbed from the ruminal wall to the blood. Factors affecting cellulose digestion 1. Types of animal, cellulose is digested in rumen of ruminants animals and large intestine of horse. 2. The presence of microorganism. 3. Types of ration "sugars and starchs affect" decrease the cellulose digestion because the microorganism perfer sugars than starch and starch than cellulose. 4. Time of exposure of cellulose in the rumen to digest by microorganism long time stay is Rumination After food enters the rumen, it is thoroughly mixed, macerated and fermented. At intervals portion of the food are regurgitated, remasticated, reinsalivation and then reswallowed. These forms the rumination cycle. It starts after 30 minutes from feeding. The phases of rumination: 1- Regurgitation The food is returned to the mouth comes from the rumen and reticulum, the enterance of ingesta into the esophagus is accompanied by: a) Inspiratory effort with a closed glottis, results in drop in intrapulmonary, intrathoracic, and intra esophageal pressures. The pressure in the rumen being high, due to contraction of abdominal muscles. 50 b) The presence of ingestia in the cardia is aspirated through the dilated end of the esophagus which in turn stimulate the vagus nerve "antiperistaltic wave in the esophagus", so the ingesta pass to the mouth. 2- Remastication The normal mastication rate is about 94/min. in normal remastication is 55/min. 3- Reinsalivation The salivary secretion is increased but the submaxillary gland is inactive. The bolus grows in size and after reach certain size, it reswallowed or redeglutition. 4- Redeglutition "reswallowed" The ruminated bolus is reswallowed and returns to the rumen, and enter the reticulum by its high specific gravity, then rumination cycle is repeated the rumination process occupies about 7-10 hours/day according to the ration feed. but decrease to 2.5 hours in feeding concentrated ration. Factors control rumination 1. Rumination centre in the medulla oblongata (M.O). 2. Vagus nerve, section of vagus, leads to loss of rumen movemnts. 3. Ration must contain sufficient amount of roughage. 4. The animal must be calm and rested and in healthy conditions. So the rumination is stopped in the following conditions. a) Presence of sharp edge of teeth. b) Fever, impactation, tympany, "pathological factors". c) Also in female during estrus phase of estrous cycle "physiological factor". 51  Behavioral physiology Introduction Behavior is a function of entire nervous system not of any particular portion, moreover, spinal cord reflexes are an elements of behavior and the wakefulness and sleep cycle are most important of animal and human behavioral patterns. However, in this chapter reviews the physiological bases e.g. emotion , sexual behavior ,fear, rage , motivation , drive and stress , also the relation of major neurotransmitter system in the brain to these processes. These functions of the nervous system are performed mainly by sub cortical structures located in the basal regions of the brain. e.g. limbic system. The hypothalamus and its related structure also control many internal conditions of the body as well as aspects of behavior such condition as body temperature ,osmolality of body fluids that drive to eat and drink. The nervous system and the endocrine system are cooperate with each other through the processes of neural secretion and through the priming effects of hormones on the brain. The animal behavior produce in response to main factors :- a) Environmental b) Internal state of the animals. Behavior is one set of activities by which animals maintain activities themselves e.g. finding food, avoids danger, urge to mate and perhaps rearing offspring. However, behavior is a mixture of inherited reflexes components which can mix and give results. Behavior requires a) Sense organs (receptor ) which collect information about changes in the internal an external environment through their stimulation. b) Inform the nervous system through nerve impulse c) Stimulation of the effecter organs such as gland and muscles Role of nervous system Information about internal and external environment concerning an animals passes to the CNS through stimulation of sensory receptors which stimulated chemically, thermally and mechanically. The sense organ stimulated by adequate level produce excitation which transmitted as nerve impulse in the form of electrically active waves on the nerve fibers. We have two main types of receptors which provide information a) Interoceptors b) Exteroceptors Interoceptors :- this one located within muscle ,joints ,tendons and internal organs. The principle sense organs determing animal behavior include the organ of sight ,smell and hearing. Exteroceptors :- these are originated outside of the animals. They include receptors found in the skin as well as the organ of vision , hearing and smell. The receptor of eye ,ear and nose are sometime refereed to as teloceptors which can dial with stimuli originated at distance from the animals. 52 -LIMBIC SYSTEM The limbic lobe or limbic system consists of a rim of cortical tissue around the hills of the cerebral hemisphere and a group of associated deep structures like amygdala, the hyppocampus, and the septal nuclei. This part of the brain is responsible for smell, it is made up of primitive type of cortical tissue (allocortex). The remaining non-limbic portions of the hemisphere are called the neocortex, which reach its greatest development in humans. The functions of the limbic lobe can be summarized as follows: One- Smell sensation. Two- Feeding behavior. Three- Sexual behavior Four- Emotion of rage and fear. Five- Motivation. One- Feeding behavior: The limbic lobe and the hypothalamus both are integrated in the regulation of the feeding behavior in animals, stimulation of the amygdaloid nuclei causes movements such as chewing, licking and other activities related to feeding. While lesion in the amygdala cause moderate hyperphagia, with indiscriminate ingestion of all kinds of food even if it is not suitable for the animal. Two- Sexual behavior: Copulation is made up of a series of reflexes integrated in the spinal cord, but the behavioral components that accompany it, like the urge to copulate, and the coordinated sequence of events in the male and female that lead to pregnancy are regarded to a large degree in the limbic system and hypothalamus. In male, bilateral limbic lesions in the pirform cortex (overlying the amygdala) produce intensely sexual activity and males of one mammalian species have been found to copulate with females of other species and even attempt to copulate with inanimate objects. The complete absence of testosterone causes the behavior to cease. In the female, the limbic system does not seem to play an important part in sexual behavior but selective ablation of anterior hypothalamic areas destroys behavioral heat. 53 Figure 23. Comparison between the size of the limbic lobe in animals and humans. Three- Emotion of rage and fear Fear and rage are closely related emotions. The external manifestations of the fear, fleeing, or avoidance reaction in animals are autonomic responses such as sweating and papillary dilatation, cowering, and turning the head from side to side to seek escape. The fear reaction can be evoked by stimulation of the hypothalamus and the amygdaloid nuclei. Conversely, the fear reaction and its autonomic and endocrine manifestation disappears when the amygdala is destroyed as in cases of monkeys who are terrified by snakes, after bilateral lobotomy, monkeys approach snakes without fear pick them up, and even eat them. The rage, fighting, or attack reaction is associated in the cat with hissing, spitting, growling, piloerection, and papillary dilatation. Most animals maintain a balance between rage and its opposite, the placidity. Major irritations make the animal loose his temper. But minor stimuli are ignored. Bilateral destruction of the amygdaloid nuclei causes in monkeys a state of abnormal placidity. Also similar responses are seen in cats and dogs. While the stimulation of some parts of the amygdala in cats produces rage. In these emotional responses the hypothalamus is also involved as the placidity produced by amygdaloid lesions in animals is converted into rage by subsequent destruction of the ventromedial nucleus of the hypothalamus. Gonadal hormones appear to affect aggressive behavior. In animals, aggression is decreased by castration and increased by androgens. It also conditioned by social factors; it is more prominent in males that live with females and increases when a stranger is introduced into an animal’s territory. Four- Autonomic effect: Limbic system produce-autonomic effect specially changes in blood pressure and respiration these effects are part of emotional response. Five- Motivation, (Pleasure): When certain parts of the human brain are electrically stimulated, a sensation of pleasure or relaxation is felt. This is termed motivation in lower animals because it is unknown if they sense pleasure as humans know it. Experiments in animals were performed in which the animal was allowed to electroshock certain parts of the brain at will. When the stimulating electrodes are placed in certain areas including the amygdala, tegmentum metal nuclei and midbrain, laboratory rats who area able to evoke the electroshock stimulus by pressing a movable bar inside the cage press that bar from 5,000 to 12,000 times per hour, and monkeys press that bar up to 17,000 times per hour. Some animals go without food and water to press the bar for brain stimulation, and some will continue until they fall over exhausted. 54  Thalamus The thalamus is ovoid body that lies against and forms the lateral wall of the 3rd ventricle. It is a collection of neurons in the white matter. Function of the thalamus: One- It is one of the main sensory systems. It forms with the sensory cortex one unit for receiving sensation. All pathways conveying conscious sensation coming from the opposite half of the body synapse in the thalamus with the exception of the olfactory system so thalamus in this way considered as a relay of sensation or pathways only. Two- It is concerned with the crude form of sensation of pain, temperature and touch e.g. the thalamus informs us if the body is hot or cold but cannot differentiate more accurately between finer difference of temperature, also the thalamus can manifest crude pain, but it cannot denote its origin exactly. So the thalamus in this case can be consider as a center. Three- Relay station for the opposite cerebellum in their way to cerebral cortex. Four- Relay nuclei in which afferent pathways from the spinal cord relay on their way to the cerebral cortex. Five- Relay station in the inhibitory closed circuit between basal ganglion and cortical motor area. Six- The medial and lateral geniculate nuclei constitute the meta-thalamus and are major relay stations for the auditory and visual pathway respectively. Seven- Relay station for autonomic and emotional reaction due to its connections with the hypothalamus and limbic lobe. Hypothalamus Is a very complex region of the brain is involved with numerous integrative response of the animal. It is the principal area of control of homeostatic responses of the organism. The hypothalamus is divided into many nuclei like; preoptic nuclei, supraoptic nuclei, paraventricular nuclei, arcuate nucleus, median eminence and mammillary body. Also the hypothalamus has a neural connections with the posterior pituitary gland and a vascular connections with the anterior pituitary. 55 Figure 25.The different nuclei in the hypothalamus The hypothalamus performs the following functions: 1- Body temperature regulation: The hypothalamus keeps the body temperature constant through two centers: One) Heatloss center: found in the anterior hypohalamus, in hot atmospheric temperature there is vasodilatation of cutaneous blood vessels, sweating or panting in dogs and cats. This occurs through stimulation of cutaneous thermoreceptors. Two) Heat production center: found in the posterior hypothalamus, stimulated by cold weather resulting in vasoconstriction of skin blood vessels, shivering and increase muscle tone and increase secretion of thyroid and adrenal glands. 2- Regulation of water balance Lateral hypothalamus has osmoreceptors and volume receptors. Hypertonicity of the blood or decrease in the blood volume stimulates these receptors which enhance the secretion of antiduiretic hormone (ADH) from the posterior pituitary. This hormone increases water reabsorption from the renal tubules. Also it was found that lesions of some areas of the hypothalamus diminish or abolish fluid intake, so the sensation of thirst is controlled by the hypothalamus as injection of hypertonic saline into the anterior hypothalamus causes drinking in conscious animal. Autonomic control One) Stimulation of the anterior hypothalamus produce para- sympathetic effect e.g. bradycardia and pupillary constriction. 56 Two) Stimulation of posterior hypothalamus produce sympathetic effect e.g. secretion of adrenaline and nor adrenaline, vasodilatation of skeletal muscle, pupillary dilatation and rise of blood pressure. 1- Regulation of food intake: The hypothalamus contains feeding and satiety centers, stimulation of satiety center inhibit the feeding center and through this reversal inhibition the food intake is regulated. There are many theories that interact for regulation of food intake that includes: One. The glucostatic theory: The satiety center is sensitive to glucose utilization, and it depends on insulin for burning of glucose despite the other parts of the brain. If glucose level is low the satiety center is inactive and the feeding center is freed from the inhibitory effect of satiety center and the animal seeks for food. After eating the glucose level rise and this leads subsequently to rise in the blood level of insulin that increase the glucose utilization in the satiety center and the satiety center becomes active. The activity of the satiety center leads to inhibition of the feeding center and the animal stop eating. Two. The gut peptides theory: after eating many gastrointestinal hormones are liberated specially CCK-PZ which induce stimulation of the satiety center and inhibit food intake. Three. A lipostatic theory arises recently to regulate food intake. Through this theory a hormone polypeptide in nature recently isolated from blood called leptin. This hormone is secreted from the fat cells in the body when engorged with fat and leads to stimulation of the satiety center and inhibition of the feeding center. During under nutrition the fat cells contain less fat and leptin secretion is minimal and animal appetite is great. After feeding the fat cells becomes full of fat and leptin secretion is high and satiety center is stimulated and the animal appetite is depressed. These factors altogether are responsible for regulation of amount of food the animal consumes. 5- Relation to cyclic phenomena: Lesions of the suprachiasmatic nuclei disrupt the circadian rhythm in the secretion of ACTH and melatonin. In addition, these lesions interrupt estrus cycles in laboratory animals, as this nucleus receive an important inputs from the eyes via the retinohypothalamic fibers, and it appears that they normally function to entrain various body rhythms to the 24 hours light-dark cycle. In diurnal animals (that become active during the daytime) the ACTH is secreted early in the morning and melatonin in the night. While the reverse is correct for nocturnal animals (animals that become active during dark) like the cat and rats, the ACTH controlling the cyclic phenomenon is adapted to be released at the begging of the night and melatonin in the early morning. ACTH is the hormone secreted from the anterior pituitary gland and stimulates the adrenal cortex to secrete glucocorticoids (cortisol) from the adrenal cortex and is responsible for elevating basal metabolic rate and increases the activity of the body. While melatonin is responsible for initiation sleep and secreted form the pineal gland. 6- Control of reaction to emotions: The hypothalamus is a center for integration of complex autonomic and somatic reactions to emotions, while the cerebral cortex is needed for feeling emotions. The sense organs and neocortex stimulate the limbic system and hypothalamus. Normally the cerebral cortex inhibits the hypothalamus rage center and the temperament of the animal depends on a balance between inhibition of cerebral cortex and the normal 57 excitatory effect of rage center. Release of the hypothalamus from the inhibitory effect of cerebral cortex by decortication in animal and application of a mild stimulus will result in an exaggerated violent reaction in the form of generalized sympathetic over activity together with somatic reactions. 7- Metabolic regulation Decrease in blood glucose level leads to stimulation of glucose receptors found in the hypothalamus, which subsequently stimulate: 1- The adrenal medulla to secrete adrenaline which triggers glycolysis. 2- Stimulate ACTH secretion to stimulate glucocorticoids secretion. 3- Stimulate hunger pains by stimulating vagus nerve and so eating is required. 8- Role in sleep The hypothalamus plays a role in sleep plus many other parts including the reticular activating system (RSA), and cerebral cortex. 9- Relation to the pituitary gland One) anterior pituitary: The hypothalamus regulates the secretion of the adenohypophysis through the release of the releasing hormones like, CRH, TSH-RH, GH-RH, Gn-RH. In addition to prolactin inhibiting hormone. Two) Posterior pituitary: The hypothalamus secretes ADH in response to changes in the blood osmolality. Also a reflex initiated from touch receptors located in the udder, uterus and genitalia enhances the secretion of oxytocin from the hypothalamus. 11- Regulation of sexual function: Hypothalamus secretes gonadotropins releasing hormones, which stimulate the secretion of pituitary gonadotropins to regulate function of gonads. Metabolism of the CNS The central nervous system depends to a great extent on glucose as the primary source of energy. Glucose transport to the nervous tissue is through facilitated diffusion across the cell membrane of the nerve cells. The brain tissues (except some areas in the hypothalamus) do not depend on insulin to facilitate glucose influx to the cells. This is great advantage to the diabetic patients, which lack insulin, because it enables normal CNS functions to continue when other systems fail due to lack of insulin. Although the brain in human constitutes only 2% of the body weight it receives about 13% of the total cardiac output and consumes about 20% of the total oxygen supplied to the body. And this reflects the higher rate of metabolism of that vital organ. The metabolic rate of the gray matter is four times that of the white matter. Orgenization of behavior Part of frontal lobe anterior to the premater area and extended to the orbital surface (prefrontal cortex )is though to be the site of integration of the information about the external words sent to the cortex along the visual, auditory and somato-sensory pathway with the information from the hypothalamus and limbic system. Behavior in turn is thought to reflect the integration of the information. Relation between hormones and behavior Hormonal state can affect both the form and intensity of behavioral responses. Hormones can affect behavior through many mediating mechanisms include hormonal effects on sensory receptors areas , on the general metabolic state and so on 58 the brain. Changes in the brain functioning induce effects on the endocrine function of having certain experiences. Although hormones can effect behavior through multiple mediating mechanisms, behavioral activity depends on the neuronal activity, although non-neural action must be integrated by the brain before behavior will be affected. Neuropeptide are chemical messengers which act on nervous system. The nervous system and the endocrine system clearly adapted for different roles , but contact between them is essential in their full function since they are independent. The two system cooperate each other through the neural secretion and through the priming effects of hormones on the brain. Hormones secreted are influenced by three types of stimulation :- a) Interaction between the animals own activities ( behavior) b) Environment ( external behavior ) c) Internal physiological state (internal state ) Any of these three factors can alter so as to cause a change in other Effects of general hormones on behavior Some of these hormones are :- 1) Thyroid hormones increased metabolism and activity of nervous system and reproduction. Thyroxin is essential for regulation and length of estrous cycle. 2) Both testosterone in the male and estrogen in female increase libido. Also injection of estrogen in the anterior hypothalamus of some lower animals cause estrous behavior ( heat). Threshold level of female sex hormone affect the animal behavior response (signs of estrous typical). Testosterone is responsible for typical male behavior ( sex drive libido ) 3) ACTH when injected into the brain of an animals cause intense fear. Sometime circadian of cortisol output in farm animals can be di-arranged as a result irregularities in ACTH output resulting from major husbandry disturbance. 4) Injection of nor-epinephrine or excess secretion of nor-epinephrine or epinephrine by adrenal medulla increase the brain activities. 5) Hypothalamus control rhythmic phenomena and sexual behavior e.g. gonadotrophin releasing hormone act on the anterior pituitary cause it to produce and release LH and FSH which operate cyclic ovarian activity and related behavior. The output of GN-rH is fundamentals importance in reproductive behavior. 6) Prolactin is concerned with the reproductive function and evoke maternal drive also promote grooming behavior. 7) Oxytocin is known as milk letdown hormone, play essential part in labour. Secreted due to stimulation of cervix and mammary region of nursing female. 8) Vasopressin associated with ACTH participation in stress response. It is a neuropeptide act as neurotransmitter aid memory, improve attention , performance and learning. 9) Melatonin output is influenced by photoperiod and is basic to the numerous cycle, seasonal phenomena and reproductive activity. 10) Placenta in addition to steroid hormone secretion, it secrete B-endorphins which induce opioid state to block pain of parturition. 11) Cortisol reduce the stressful effect. This hormone increase blood glucose levels for the need of sudden energy demands. 59  12) Adrenaline prepare the animals for gross physical activity in emergency situation ,increase in blood pressure in response to stressful stimulation and in agonistic events in general and specific form e.g. fighting and maternal protection. Adrenaline produces a basis for alarm response. Chemical transmitter system for behavior control Several species collection of neurons in the brain each release a specific chemical transmitter substance, three of them have particular attention as behavior modifiers , these are : a) Nor-epinephrine system. b) Serotonin system. c) Dopamine system. It notice that decrease formation of either nor-epinephrine or serotonin or both appear symptoms of grief , unhappiness, despair and misery , in addition loss their appetite and sex drive and also have insomnia. The principle reasons is that drugs block the secretion of nor-epinephrine and serotonin e.g. reserpine and lithium compounds. It was found that nor-epinephrine and serotonin normally function to provide motor drive to the limbic system to increase a presence sense of well being, to create happiness ,good appetite ,contentment , sex drive , psychomotor balance ,schizophrenia might be caused by excessive secretion of dopamine in the brain. When parkinsonism disease patient are treated with L-dopa which release dopamine in the brain. The Parkinson's patient sometime develops schizophrenic symptoms , indicating that excess dopamine can cause dissociation of a persons drives and thought patterns. Pheromones and behavior Pheromones are chemical compound produced by an sex and detected by the other sex and increase their sexual desire of the animals and affect the behavior of the animals. During estrus, the decomposition of sloughed keratinizing epithelium lining the vagina of female by vaginal bacteria give volatile fatty acid specific for species. Boar and bull seek out the estrus female from large herd by olfaction , male dog are attracted from great distance by estrus female. These pheromones are of many kinds :- 1) The volatile fatty acid produced in the vagina of the female attract the male. 2) The tarsal gland on the inside of the hind legs transmit odors to identify the foreign individual in the herd. 3) Rabbits have scent glands on their chest and around anus. 4) Cats have special gland on their forehead. 5) Some herbivores have scent gland in their foot pads. In nasal septum lies a specialized organ called vomeronasal organ that responsible for perception of pheromones that affect sexual activity of the animals. Pheromones are considered a chemical language among animals for certain purposes such as marking boundaries of territories , recognizing individual from some herd and nest ,emitting alarm and making the location of food , serve to synchronize the reproductive activities of both sexes , attraction ,repulsion and parturition care stimulation. 60  Pheromones induce rapid alteration in behavior and endocrine pattern of the animals as elevate levels of epinephrine ,dopamine and LH while it decline prolactin and stimulatory effect of the hypothalamo- pituitary –gonadal axis , maternal behavior during lactation as well as social interaction are under control of pheromones. Environmental factors (photoperiod, temperature ,nutrition ,season of year ,circadian rhythm and hormonal pattern of the body regulate release of pheromones ) Homeostasis and behavior The term homeostasis is the process that maintain the stability of internal environment while performing all its function which may be influenced by external factors or independent of external condition. A homeostatic mechanism is a regulating mechanism stimulated by alteration in some physiological property or quantity which acts to produce a compensating changes in the opposite direction. The stimuli elicited from the external environment as solar radiation ,humidity , air movements , rain fall, day length, or posture requires :- 1) Detector (receptors ) often specialized to respond to particular variables. 2) Conduction of impulses through afferent nerve to the hypothalamus and CNS. 3) Coordinating and integrating mechanism (nervous and hormonal). 4) At the hypothalamus and CNS there are two types of receptors :- a) Fast receptors b) Slow receptors a) The fast receptors which give the animal response as behavioral reactions, stimulation of cardiovascular and respiratory system. b) Slow receptors which stimulate the endocrine system , metabolic process and enzymatic mechanism. All of the above factors coordinates in order to adjust and readjust the internal environment of the animals (homeostasis mechanism and resulting in energy ,chemical and circulatory balances). Stress It is non specific response of the animal body to an environmental effects which exhaust control system and reduce its fitness ( increase mortality and failure to grow or to reproduce ). Types of stressors 1) Animal transportation by train ,plain or truck. 2) Contamination of water and feed with fungi and release of aflatoxins 3) Thermal stress which is the major factors. 4) Management stress e.g. lake of sanitation , poor ventilation and careless handling. 5) Deprivation of water ,food , unbalanced