BIOL 2510 notes week of 2.22.16
BIOL 2510 notes week of 2.22.16 BIOL 2510 - 012
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This 7 page Class Notes was uploaded by Laura Nall on Thursday February 25, 2016. The Class Notes belongs to BIOL 2510 - 012 at Auburn University taught by Jeffrey Goessling in Winter 2016. Since its upload, it has received 208 views. For similar materials see Human Anatomy and Physiology II in Biology at Auburn University.
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Date Created: 02/25/16
o Regulation of gastric secretion Three sites of stimuli. Inhibit or enhance secretion Cephalic phase: before food enters stomach o Smell, taste, site, thought of food o Vagus nerve stimulates stomach Gastric phase: 34 hours, food in stomach o Stimulation Stretch receptors Chemical changes cause G cells to release gastrin Partially digested proteins, caffeine, increased pH o Inhibition Low pH inhibits gastrin secretion Empty stomach, stress adrenal responses Intestinal phase: food entering duodenum o Stimulation (brief!) Influx of chyme triggers intestinal gastrin release o Inhibition Distension, acidic, fatty, or hypertonic conditions Liver o Largest gland in body o Filtration system for digestive system o Functions Produces bile for fat digestion Bile salts – emulsify fats Lecithin – phospholipids that also emulsify fats Filters blood Hepatic artery and hepatic portal vein sinusoids hepatic vein inferior vena cava right atrium Gallbladder o Functions: stores and concentrates bile o Empties from: Gallbladder cystic duct common bile duct duodenum Pancreas o Function: produces digestive enzymes for fats, carbs, and proteins o Pancreatic juice empties into duodenum via main pancreatic duct o 2 cell types 1. Islets of Langerhans – endocrine cells, produce and releases hormone a cells (alpha cells) – glucagon (breakdown glycogen to make glucose) o increases plasma glucose levels B cells (beta cells) – insulin (signals glucose uptake by cells) o Decreases plasma glucose levels 2. Acinar cells – exocrine cells, produce enzymes and produce/store inactive enzymes (zymogens) Inactive enzymes: o Trypsinogen o Chymotrypsinogen o Procarboxypeptidase Other enzymes: o Pancreatic amylase – carbohydrate; starch, oligosaccharides to disaccharides o Pancreatic lipase – lipid; triglycerides to monoglycerides and fatty acids o Regulation of bile and pancreatic secretion – by secretin and CCK Secreten Secreted when chyme enters duodenum Stimulates o Secretion of bile from liver cells o Secretion of pancreatic juice from pancreatic acinar cells Cholecystokinin (CCK) Secreted when chyme enters duodenum Stimulates o Contraction of gall bladder – secretes bile into bile duct o Secretion of pancreatic juice from pancreatic acinar cells o Relaxation of hepatopancreatic sphincter so pancreatic juice and bile can enter duodenum Small intestines – gross anatomy o Major functions: complete digestion and absorption of nutrients o ~20 t long with 3 divisions: Duodenum – receives chyme from stomach, pancreatic juice, and bile ~10 inches Most absorption Jejunum – middle portion ~8 feet long Ileum – last region of small intestine, joins large intestine at ileocecal valve (sphincter) ~12 feet long Small intestines – micro anatomy o Adaptations to increase surface area for nutrient absorption Circular folds – deep folds of the mucosa and submucosa that slow movement of chyme Villi – fingerlike projections of mucosa, its epithelial cells are absorptive cells Crypts of lieberkuhn (aka intestinal crypts) o Tubular glands between villi o Epithelial cells are secretory cells – secrete intestinal juice (water, mucus, rush border enzymes) o Enteroendocrine cells secrete CCK and secretin Microvilli – tiny bristlelike projections of absorptive cells “brush border” Small intestines – absorption o Carbohydrate absorption Apical side – cotransport with Na+ Basolateral side – facilitated diffusion Fat emulsification and absorption 1. Bile salts and lecithin in duodenum break up (emulsify) fat globules into small droplets 2. Lipase breaks fats into monoglycerides and fatty acids 3. Bile salts and lecithin surround monoglycerides and fatty acids creating micelles 4. At apical surface of epithelial cells, lipid substances move into cells by diffusion 5. In epithelial cells converted back into fat (triglycerides) and combined with cholesterol, phospholipids creating chylomicrons 6. Chylomicrons transported to lymphatic capillaries via exocytosis Large intestines o From ileocecal valve to anus o Major functions: Water absorption by osmosis Feces production o Subdivisions Cecum – saclike first portion below ileocecal valve Appendix – mass of lymphoid tissue that extends from cecum Colon – 4 regions o Ascending – up right side o Transverse – across abdomen o Descending – down left side o Sigmoid – sshaped where enters pelvic and joins rectum Rectum Anal canal – 2 sphincters with skeletal and smooth muscle o Gut microbiome – commensal bacteria in large intestines Functions: Synthesize B & K vitamins Ferment undigested carbohydrates (yields gas) Keeps pathogenic microbes in check Interacts with immune system Affected by diet Prebiotics – food for good bacteria Probiotics – the good bacteria Question: Which structure of the small intestines are tiny projections that give the mucosal surface a “silky” feeling? Microvilli The absorption of carbohydrates and amino acids utilizes a _________ cotransport system. Sodium (Na) Chylomicrons are directly absorbed into blood (T/F). False they are absorbed into lacteles Amino acids are directly absorbed into blood (T/F). True Conditions and diseases of the digestive tract Hepatitis – inflammation of liver o Types AF 40% of cases in U.S. are Hepatitis B (exchanged through needles) 32% cases are Hepatitis A Type C is the most common o Causes Mostly viruses Toxins (alcohol and medications) o Fibrosis (scarring) o Cirrhosis – chronic inflammation Gastric ulcers o Erosion of stomach wall o Cause: Helicobacter pylori o Treatment: antibiotics Heartburn o Gastroesophageal reflux disease (heartburn) Causes: acidic gastric juice to go up esophagus due to Excessive eating, drinking Pregnancy Hiatal hernia – part of stomach bulges through the hiatus above diaphragm Why doesn’t acidic juice affect stomach lining? Gastric mucosal surface Gallbladder conditions o Gallstones Low bile results in cholesterol crystallizing in gallbladder Crystals can block cystic duct o Jaundice Accumulation of yellow bile pigments in blood Can be due to bile duct blockage o Diarrhea Too fast digestion Too much water o Constipation Too slow digestion Not enough water Chapter 24 – Digestive system part II Nutrition and metabolism 1. Nutrients – substances in foods the body needs for growth, maintenance, repair 2. Energy of food measured in kilocalories (kcal) – amount of heat energy needed to raise the temperature of 1 kg of water 1 degree C 3. Metabolism – chemical reactions occurring in the cells a. Anabolism – reactions whereby smaller molecules assembled into larger molecules or structures b. Catabolism – processes that break down complex structures into simpler ones Nutrients 3 macro: o Carbohydrate o Lipid o Protein 2 micro: o Vitamins – organic molecules Function as coenzymes Most dietary D made in skin B and K synth by intestinal bacteria A converted from betacarotine o Minerals – structure (e.g. bone) and ion balance (e.g. action potentials) Ca, P, K, Su, Na, Cl, Mg Carbohydrate metabolism Digestion: poly, oligo, disaccharides monosaccharides (all converted to glucose in liver) Glucose enters cells by facilitated diffusion Fate in fed state: o ATP production (cellular respiration) o Glycogenesis – glucose combined to form glycogen Most glycogen produced and stored ni liver and skeletal muscle o Lipogenesis – formation of triglycerides Glucose used to form triglycerides and stored in adipose tissue ATP synthesis Aerobic pathway – net product is 32 ATP o Steps: Step 1: glycolysis Step 2: Krebs cycle Step 3: oxidative phosphorylation o Pros: Yields lots ATP for each glucose Provides energy for hours of activity! o Cons: Slow process Needs oxygen o C6H12O6 + 6O2 6CO2 + 6H2O gives off 32 ATP Step 1: Glycolysis Occurs in cytosol Is an anaerobic process Steps: o Glucose phosphorylated to glucose6phosphate then converted to fructose1,6 biphosphate (ATP requiring processes) o Fructose1,6biphosphate cleaved into two 3carbon fragments o 3carbon fragments oxidized (give up H+) o NAD+ is reduced (picks up the H+) forming NADH NAD+ (nicotinamide adenine dinucleotide) is a coenzyme – activate enzymes and serve as hydrogen (or electron) acceptors o ATP formed by substratelevel phosphorylation – P from 3carbon fragments added to ADP END PRODUCTS: 4 ATP (NET = 2), 2 NADH, 2 Pyruvic acid Step 2: Krebs cycle Occurs in mitochondria st Pyruvic acid 1 converted into acetyl coenzyme A (acetyl CoA) Acetyl CoA enters Krebs cycle Krebs cycle: o Carbons removed from acetyl CoA (& subsequent substrates) o Acetyl CoA (& subsequent substrates) oxidized o NAD+ & FAD (Flavin adenine dinucleotide; another coenzyme) reduced forming NADH & FADH2 o 1 molecule of ATP formed by substrate level phosphorylation for each “turn” of cycle END PRODUCTS (per ONE pyruvic acid molecule): 3CO2, 1 FADH2, 4 NADH, 1 ATP How many ATP produced for each glucose molecule? 2 ATP Step 3: oxidative phosphorylation Via electron transport chain at the inner mitochondrial membrane FADH2 and NADH give up H atoms to enzyme complexes within membrane H atoms split into proton and electron o Electrons get passed down successive complexes, combine with O to form H2O o Protons pumped into intermembrane space H+ travel through ATP synthase providing energy for P to be attached to ADP END PRODUCTS: 28 ATP and H2O
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