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UA ECOL 437 - Vertebrate Physiology

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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Lecture 24, 25 Nov 2003Chapter 15, Feeding and DigestionChapter 16, Energy Expenditure?Vertebrate PhysiologyECOL 437University of ArizonaFall 2003instr: Kevin Boninet.a.: Bret Pasch1Vertebrate Physiology 4371. Feeding and Digestion (CH15)2. ~Energy Expenditure (CH16)?3. Announcements… - Exams returned Wed. - Term paper 04 Dec. - Seminar write-up 09 Dec. - Powerpoint practice (file to us on 09 Dec.) - Oral Presentations 10 Dec. - Wed assignment~ 4 short questions on website Wed. midday (-25%? and extra question if absent)2(15-36)Generalized Digestive System(15-13)123412 (incl. stomach)34Salivary glands (mucin) to lubricateTongue for chemoreception3REVIEWForegut-Conducting, Storage, Digestion-Esophagus and StomachCrop in some for storage/regurgitationStomach- begins digestion (e.g., pepsin)- food storage- mechanical mixing (muscular walls)- Monogastric (1 chamber, carnivores and omnivores)- Digastric (> 1 chamber)e.g., Some birds use to grind with pebbles and sand4REVIEWForegutMonogastric Stomach- strong muscular sac/tube- sphincters at both ends- mucus from goblet cells of gastric pit- HCl from parietal cells of gastric gland- pepsinogen from chief cells of gastric gland(15-17)5REVIEW112233ForegutDigastric Stomach- herbivores- anaerobic fermentation by symbiotic bacteria and protozoans(15-18)- regurgitation1234- digestive enzymes( Carbohydrates -> sugars and gases ) sugars, amino acids, short FAs into bloodDomestic cattle, 1L/min gas! (methane and CO2)6REVIEWMidgut-Chemical digestion and Absorption (~ small intestine)-from stomach through pyloric sphincter into duodenum-alkaline 1-Duodenum (mucus + secretions from liver, pancreas) Bile duct from liver-Bile breaks up fats and neutralizes acids Pancreatic Juice-proteases, lipases, carbohydrases, antacid2-Jejunum (digestion and absorption)3-Ileum (mostly absorption)-Internal symbionts help digest, provide nutrition, vitamins-Gas exchange in some air-breathing fishes7(15-31)MidgutAnatomy:-longitudinal smooth muscle-circular smooth muscle-epithelium -submucosa (connective tissue) -mucosa (mucous membrane)(15-19)Epithelial cells sloughed rapidly(2x1010 cells/day),lining replaced every few days8Midgut-Intestinal Epithelium, SURFACE AREA-aids absorption of digested nutrients-epithelium arrangement: -circular folds -villi with blood vessels -central lacteal (lymph system)-microvilli (2x105 per mm2)(15-19)(15-20)9Midgut-Intestinal Epithelium, SURFACE AREA-intestinal chyme-surface of microvilli: -covered with glycocalyx -mucus and water mixed in -absorption through epithelial cells-microvilli with actin, interacts with myosin for movement(15-20)10(15-20)Villi with microvilli(brush border)11Hindgut-Water and Ion absorption; Defecation-reabsorb water and ions at end of small intestine (ilieum) and from large intestine/colon-feces into cloaca/rectum for excretion-cloaca can also be site of urine modification (e.g., birds)-bacterial digestion in hindgut fermenters (especially in cecum)-coprophagy/cecotrophy (e.g., rabbits)12Hindgut-Water and Ion absorption; defecationhorserabbithindgut fermenters(15-22)13Gut PlasticityAlter gut size, activity (reversible)-Sustained increased metabolism can increase bird gut length by 1/5-Mammals increase GI tract mass 3-4x post-hibernation14(everted sleeve)Gut PlasticityAlter gut size, activity (reversible)-Some infrequently-feeding snakes: - intestine 2x larger within 2 days - microvilli length and area up 400% - glucose transport rate up as much as 22x - other transporters also up-regulated (e.g., a.a. absorption)(15-23)15MotilityContraction of gut and movement of contents:1. Propulsion, expulsion2. Mixing and grinding (enzymes, mechanical digestion)3. Stirring so brush border/epithelial lining gets nutrientsPeristalsis -longitudinal muscle -circular muscle(15-24)Move food along...16(15-25)Regurgitation, Vomiting?KneadingMovement17MotilityControl of smooth muscle contractionIntrinsic-pacemaker activity (basic electric rhythm = BER)-stretch-chemical signals from chymeExtrinsic-GI peptide hormones-autonomic NS(Myenteric and submucosal plexus)Sympathetic and Parasympathetic innervation18Intrinsic-pacemaker activity (basic electric rhythm = BER)-cations and Ca2+(15-26)19ExtrinsicMyenteric and submucosal plexus(15-27)Parasympathetic (~ACh)-increased motility-increased secretionSympathetic (~norepi)-decreased motility-decreased secretionOther neurotransmitters also20Los SecretionsAlimentary canal is largest endocrine and exocrine glandSalivary glandSecretory cells of stomach and intestineSecretory cells of liver and pancreasWater, ions, mucus, enzymesBile (fat digestion) -created in liver, stored in gall bladder -also gets rid of some waste products metabolized by liver -Why is your poop brown?21(15-31)(proenzymes)Los Secretions22Los SecretionsDigestive Enzymes hydrolyze larger molecules:e.g., Sugars (glycosidic bonds) into monosaccharidesProteases (protein peptide bonds -> amino acids)-endopeptidases-exopeptidases~specialized (e.g., Trypsin cleaves arg. or lys.)Pepsin (from pepsinogen in acid, ~pH=2 envir.)23Los SecretionsCarbohydrasesa. Amylases -salivary glands, pancreas, stomachb. Glycosidases -absorptive cells, glycocalyx, disaccharides (midgut)Cellulase -symbiotic microorgansims(15-33)24Los SecretionsLipases1. Break up insoluble fats using bile salts etc.2. Formation of micelles (small lipid spheres)3. Lipases cleave lipids into fatty acids plus mono- or diglycerides2526Control of Los SecretionsPresence of Food stimulates:Chemoreceptors lead to activation:1 Autonomic Efferent Neurons2 GI hormones into blood stream-stimulates liver, pancreas, gutMental influences-conscious decisions-learned smells, sounds -Pavlovian responseGastrointestinal secretions controlled by hormones:-endocrine cells of gastric and intestinal submucosa-complicated, varies in areas of gut2728Los Secretions (order and triggers)SalivaryWater, electrolytes, mucin, amylase, antimicrobialsDecreased salivation in response to sympathetic NSGastricHCl (hydrochloric acid) from parietal cells-carbonic anhydrase -response to: 1 parasymp. stimulation 2 gastrin 3 caffeine, alcohol,


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