VPHY 3100: Week of 11/16/15
VPHY 3100: Week of 11/16/15 VPHY 3100
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This 10 page Class Notes was uploaded by Lorin Crear on Friday November 20, 2015. The Class Notes belongs to VPHY 3100 at University of Georgia taught by Dr. Li, Dr. Wells, Dr. Brown in Summer 2015. Since its upload, it has received 62 views. For similar materials see Elements of Physiology in Animal Science and Zoology at University of Georgia.
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Date Created: 11/20/15
Chapter 18 The Digestive System 0 Stomach o Gastric glands I Secrete gastric juice I Goblet cells 0 Secrete mucus I Chief cells 0 Secrete pepsinogen I Parietal cells 0 Secrete HCl and intrinsic factor IF 0 HCl Kills bacteria Denatures ingested proteins Necessary for conversion of pepsinogen to active pepsin enzyme Production 0 At apical membrane closest to lumen proton pump moves H out of cell into lumen and Cl is secreted into lumen by facilitated diffusion 0 Cl is cotransported against its membrane With HCO3 at basolateral membrane closest to interstitial uid Stimulation of production 0 Endocrine o Gastrin from G cells carried via blood to parietal and ECL cells 0 Neural o Acetylcholine from parasympathetic ANS stimulates parietal amp ECL cells 0 Paracrine o Histamine binds to H2 receptor 0 Antihistamines inhibit receptor and HCl production Polypeptide that promotes absorption of Vitamin B 12 in ileum of small intestine Vitamin B 12 important for production of RBCs Production of IF only essential function performed by stomach I Enterochromaffinlike cells ECL 0 Secrete histamine and serotonin I G cells 0 Secrete gastrin as hormone I D cells 0 Secrete somatostatin 0 Protection Digestion and Absorption I Protection of Stomach o Barriers to pepsin and acid 0 Physical amp Chemical 0 Mucus coat contains HCO339 0 Structural amp Cellular 0 Tight junctions between adjacent epithelial cells I Prevent seepage out of stomach o Entire epithelium replaced every 3 days 0 Prostaglandins I Decrease gastric acid I Increase mucus secretion I NSAIDs antiin ammatories reduce activity of prostaglandins I Digestion 0 Proteins partially digested by pepsin 0 Salivary amylase that digests carbohydrates inactivated by acid I Absorption 0 Only alcohol and aspirin absorbed in stomach 0 Regulation of Gastric Activities I Local regulation 0 Intrinsic nervous system 0 increases secretion of pepsinogen and HCl 0 Hormones gastrin somatostatin histamine 0 Increase secretion of pepsinogen and HCl When amino acids present I Extrinsic Neural Regulation 0 Divided into three phases 0 Cephalic phase 0 Begins With thought of food 0 Continues until first 30 min of meal 0 Secretion of gastrin and histamine o Secretion of pepsinogen and HCl 0 Gastric phase 0 When food is present in stomach o Gastric secretions increased by physical distension and presence of amino acids 0 Positive feedback loop 0 Intestinal phase 0 When food enters small intestine o Gastric activities inhibited by stretch of intestinal wall I Prevents overloading of intestine o Fats in duodenum decrease gastric activities I Increase secretion of enterogastrones CCK and GIP o Stomach Disorders Peptic ulcers 0 Erosion of mucus membrane of stomach or duodenum o Perforation hole forms through all four layers of tract 0 Treatment by proton pump inhibitors 0 decrease acidity in stomach 0 Helicobacter pylori o Bacteria residing in GI tract that may cause ulcer 0 Treatment by antibiotics Acute gastritis 0 Histamine released due to tissue damage and in ammation stimulates further acid secretion 0 Treatment by histamine receptor H2 R blockers Small Intestine 0 Structure Folding 0 Villi and microvilli 0 brush border enzymes on surface of microvilli 0 Increased surface area for absorption 0 Each villus contains capillaries and central lacteal 0 Function Complete digestion of carbohydrates proteins lipids 0 Requires pancreatic enzymes and brushborder enzymes 0 Absorption Duodenum and jejunum 0 Carbohydrates amino acids lipids iron and calcium Ileum o Bile salts vitamin B12 electrolytes water 0 Slow waves Large intestine Depolarizations Paced by interstitial cells of Caj al Slow wave opens voltagegated Ca2 channels 9 triggers action potential 9 contraction of smooth muscle Motility 0 Peristalsis 0 Movement of chyme through intestine 0 Small and weak movement 0 Segmentation 0 Major contractile activity of intestine 0 Strong contraction to mix chyme 0 Anatomy I Cecum 9 ascending colon 9 transverse colon 9 descending colon 9 sigmoid colon 9 rectum 9 anal canal 9 anus o Motility I Outer surface bulges to form haustra baglike structure 0 Function I Absorption of water and electrolytes 0 90 absorbed by small intestine 0 90 of remaining 10 absorbed by large intestine I Production of vitamin B complexes vitamin K and folic acid 0 Made by microbes 0 Also make fatty acids from cellulose I Storage of feces o Defecation i Distension of rectum by fecal matter 0 Sharp angle in rectum prevents fecal matter from constantly being pushed from sigmoid colon into rectum ii Signal sent to sacral region of spinal cord iii Internal anal sphincter involuntary and external anal sphincter voluntary relax iv Contraction of abdominal and pelvic muscles push feces from rectum 0 Regulation of Digestive Activities 0 Neural I Neurotransmission o Innervation of myenteric and submucosal plexi 0 Acetylcholine and substance P stimulate muscle contraction behind bolus 0 Nitric oxide VIP and ATP stimulate muscle relaxation in front of bolus I Intestinal re exes 0 Gastroileal re ex 0 Increased gastric activity increased motility of ileum increased movement of chyme from ileum to cecum 0 Ileogastric re ex 0 Increased distension of ileum decreased gastric motility 0 Intestinointestinal re ex 0 Increased distension of one GI segment relaxation throughout rest of intestine o Humoral I Endocrine regulation 0 Secretin o Secreted by small intestine to raise pH 0 Stimulates HCO339 secretion 0 Helps neutralize acidic chyme 0 Cholecystokinin CCK o Secreted by small intestine in response to presence of proteins and fats o Stimulates contraction of gallbladder and secretion of bile o Stimulates enzymatic secretion in pancreatic juice 0 Gastric Inhibitory Peptide GIP o Inhibits gastric motility I Paracrine regulation 0 Presence of food increased intestinal pressure increased muscle contractions Liver o Largest internal organ 0 Lobes 9 lobules 9 hepatic plates 9 hepatocytes 9 liver I Plates separated by sinusoids and bile canaliculi I Sixsided lobules have central vein in middle 0 Liver cells essentially bathed in blood from portal vein from small intestine and hepatic artery I Both empty into central vein 0 Function I Production of bile acid and bile salts o Bile bile acid bile salts electrolytes cholesterol HCO339 water 0 Cholesterol precursor 0 Aids digestion of fats o Yellowish pigment due to bilirubin o J aundice condition resulting from problem eliminating bile gives sclera of eye a yellowish appearance 0 Secreted into bile canaliculi 9 drained by bile ducts 9 stored in gallbladder I Conversion of old hemoglobin to bilirubin which is then added to bile I Metabolism of protein into urea and uric acid I Synthesis of plasma proteins and clotting factors I Glycogenesis and glycogenolysis I Metabolism of lipids I Production of ketone bodies I Drug metabolism I Hepatic portal system 0 Digested food is absorbed and delivered to capillaries in villi From there drains into hepatic portal vein and is transported to liver I Enterohepatic circulation 0 Reabsorption of 95 of bile Pancreas o Islets of langherans I Whitish dots I Secrete insulin and glucagon 0 Rest produces pancreatic juice I water HCO339 and digestive enzymes I Most digestive enzymes produced as inactive precursors called zymogens o Trypsinogen o Travels through pancreatic duct and converted to active trypsin in small intestine o Trypsin inhibitors prevent conversion of trypsinogen in pancreas o Digestion and Absorption o Carbohydrates I Digestion 0 Salivary amylase o Pancreatic enzymes 0 Digest starch to oligosaccharides 0 Brush border enzymes 0 Hydrolyze oligosaccharides to monosaccharides I Absorption 0 Only monosaccharides can be absorbed o For high luminal glucose concentration facilitated diffusion o For low luminal glucose concentration cotransport With sodium 0 Proteins I Digestion o Begins in stomach o Pepsin digests proteins to polypeptides 0 In duodenum and jejunum o Endopeptidases I Cleave peptide bonds in interior of polypeptide I Trypsin I Chymotrypsin o Exopeptidases I Cleave peptide bonds from ends of polypeptide I Carboxypeptidase I Aminopeptidase I Absorption 0 Free amino acids cotransported With sodium 0 Di and tripeptides transported via secondary active transport using proton gradient 0 Hydrolyzed into amino acids in cytoplasm and then secreted into blood 0 Lipids I Digestion o Bile secreted When lipids present in duodenum o Emulsifies lipids forms smaller fat molecules 0 Micelles formation transports digested fat in bubbles called micelles and move to brush border for absorption o Pancreatic lipase o Hydrolyzes triglycerides to form fatty acids and monoglycerides I Absorption o Transported via portal veins to liver 0 95 absorbed by liver before going to systemic circulation 0 Once absorbed by brush border triglycerides and phospholipids are resynthesized 0 Combine With lipoprotein to form chylomicrons o Chylomicrons secreted into central lacteals and travels to thoracic duct Where it mixes With blood at vena cava 0 Most of it stored in adipose tissue 0 Remainder metabolized by liver Chapter 19 Regulation of Metabolism 0 Metabolism 0 Sum of all chemical equations in body I Anabolism synthesis catabolism hydrolysis 0 Metabolic rate I Amount of oxygen consumed by body per minute 0 Basal metabolic rate BMR I Awake relaxed 1214 hours after eating at comfortable temperature I Depends on age sex body surface area thyroid hormones 0 Hyperthyroidism high BMR o Hypothyroidism low BMR 0 Energy 0 Living tissue maintained by expenditure of ATP I ATP generated by glycolysis and oxidative phosphorylation Kreb s cycle 0 Measurement I Calorie heat required to heat 1 mL of water 1 C 0 Special tissue needs I Neurons prefer glucose I RBCs can only use glucose I Resting skeletal muscles prefer fatty acids 0 During exercise use glucose 0 Nutrients 0 Essential nutrients cannot be produced by body I 8 essential amino acids I Fatty acids 0 Linoleic acid N6 or 06 o Linolenic acid N3 or 03 I Vitamins 0 Water soluble B amp C 0 Cannot be stored in body 0 Coenzymes 0 Vitamin C antioxidant 0 Fat soluble 0 Vitamin A vision development 0 Vitamin D calcium metabolism 0 Vitamin E antioxidant 0 Vitamin K production of clotting factors I Minerals 0 Free Radicals o Molecules containing an unpaired electron in outer orbital 0 Highly reactive 0 Production I In mitochondria during oxidative phosphorylation 0 Functions I Immune 0 Assist in destruction bacteria 0 Proliferation of lymphocytes I Wound healing 0 Proliferation of fibroblasts I Vasodilation o By NO39 0 Oxidative stress I Accumulation of too many free radicals I Begin to alter structure of proteins nucleic acids lipids I Promotes cell damage 9 cell death or mutation I Can cause apoptosis aging in ammatory disease degenerative disease malignant growth e g cancer I Protection against oxidative stress 0 Endogenous enzymes 0 Neutralize free radicals o Superoxide dismutase SOD 0 Vitamins o C E and Bcarotene o Adipose Tissue o Differentiation of Adipose Tissue I Adipose tissue aka fat cellsadipocytes I PPARY peroxisome proliferator activated receptor subtype v 0 Functions as transcription factor 0 Activates genes for differentiation and metabolism 0 Circulating fatty acids or prostaglandin binds to PPARY 9 increase in mitosis and differentiation of preadipocytes 9 increased number of adipocytes 0 Number of adipocytes stable by adulthood o Adipostat I Theory that negative feedback loops defend maintenance of a certain amount of adipose tissue making it difficult to lose weight 0 Energy Metabolism I Energy stored as triglycerides in adipose cells 0 Storage and release is hormonally controlled I Adipose tissue is hormonal 0 Secretes adipokines When PPARY activated 0 Regulate hunger metabolism and insulin sensitivity 0 Include adiponectin leptin TNFd resistin and retinol binding protein 4 retinol BP4 0 Leptin 0 Increased fat tissue increased leptin secretion decreased appetite o Starvation decreased fat tissue decreased leptin levels diminished immune activity 0 Certain amount necessary for fertility o Adiponectin o Insulinsensitizing antidiabetic effect 0 Decreased in obesity and type II diabetes 0 Obesity I Increased secretion of leptin TNFd resistin and retinal BP4 decreased sensitivity of muscle to insulin insulin resistance blood glucose is not absorbed type II diabetes I Childhood obesity involves adipocyte size and number I Adult obesity involves mainly adipocyte size I BMI body mass index 0 Weight lltgheight2 m2 0 healthy BMI 1925 0 obesity BMI gt30 0 Regulation of Eating Behavior I Central 0 Hunger center in hypothalamus o Secretion of neuropeptide Y NPY and agoutirelated protein AgRP increased hunger o Secretion of melanocyte stimulating hormone MSH decreased hunger 0 Increased circulating energy substrates increased MSH and decreased NPY and AgRP decreased appetite 0 Neurotransmitters 0 Promote overeating endorphins NE 0 Suppresses overeating serotonin I Peripheral 0 Stomach and small intestine o Shortterm regulation 0 Gherlin from stomach stimulates hunger o CCK from small intestine promotes satiety 0 Leptin o Satiety factor o Secretion increases as stored fat increases 0 Insulin 0 Plays role in satiety o Insulin decreased NPY decreased hunger I Hormonal o Absorptive state 0 Within 4 hour period after eating 0 Abundant energy 0 Increased insulin 0 Postabsorptive state 0 At least 4 hours after eating 0 Increased glucagon 0 Regulate balance between anabolism and catabolism