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BIOL 373 Final Exam
First Unit - correct answer ✔✔ Segmental Contraction - correct answer ✔✔mixing/churning maximizes exposure to digestive enzymes and epithelium alternate segments contract little or no net movement forward Gut Motility - correct answer ✔✔most gut muscle is a single unit of smooth muscle connected by gap junctions contract as a single unit
- Tonic contraction
- Phasic contraction Between meals: -migrating motor complexes During/after meal: -peristaltic contractions -segmental contractions Tonic Contraction - correct answer ✔✔mins to hrs
anterior part of stomach is tonically contracted
- keeps food from moving backwards)
- smooth muscle sphincters Phasic Contraction - correct answer ✔✔secs posterior stomach small intestine Slow Wave Potentials - correct answer ✔✔ Regulation of GI Function (3) - correct answer ✔✔1) Long reflexes, integrated in CNS
- short reflexes, integrated within gut (enteric nervous system)
- reflexes involving gut peptides (paracrine or travel via blood - endocrine) Secretions in the Gut - correct answer ✔✔1) water and ions (into lumen, then reabsorbed)
- enzymes
- mucus
- saliva
- bile (from liver) Secretion of Water and Ions - correct answer ✔✔(Na+, Cl-, K+, HCO3-, H+) ions secreted via membrane transporters water follows osmotic gradient paracellular route
-includes cephalic reflexes
- efferent limb always autonomic -parasympathetic: excitatory -sympathetic: inhibitory Cephalic Reflexes - correct answer ✔✔-in response to sight, smell, thought of food, effects of emotion feedforward reflex, "long" reflex part of "long" reflexes regulation of GI function Short Reflexes - correct answer ✔✔integrated within gut in "enteric nervous system"
- Regulate secretion -neurons in submucosal plexus receive signals from lumen
- Regulate motility -neurons in myenteric plexus Reflexes involving gut peptides - correct answer ✔✔1) act locally (paracrine)
- travel via blood (endocrine)
- some act on brain effects on motility -altered peristalsis, gastic emptying, etc. effects on endocrine and exocrine secretion
Myenteric (Auerbach's) Plexus - correct answer ✔✔major nerve supply to the gastrointestinal tract controls GI tract motility located in the muscularis layer between circular and longitudinal muscle Layers of GI Tract - correct answer ✔✔Mucosa (3 Layers - Epithelium, lamina propria, muscularis mucosae) Submucosa Muscularis (circular muscle, longitudinal muscle) Serosa Meissner's (Submucosal) Plexus - correct answer ✔✔located in the submucosa layer nerve supply to GI tract Enteric Nervous System - correct answer ✔✔one of the main divisions of the autonomic nervous system consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract Gut Peptides - correct answer ✔✔gut hormones secreted by enteroendocrine cells in the stomach, pancreas, and small intestine control various functions of the digestive organs Parallels between ENS and CNS (4) - correct answer ✔✔1) intrinsic neurons (similar to interneurons)
Motilin - correct answer ✔✔targets: -smooth muscle regulates migrating motor complexes Stomach Function - correct answer ✔✔M: peristalsis, mixing S: HCl, pepsinogen, gastric lipase, mucus, HCO3-, gastrin, histamine D: proteins, fats A: lipid-soluble substances (e.g. alcohol, aspi????) Oral Cavity and Esophagus Function - correct answer ✔✔M: swallowing, chewing S: saliva, salivary glands D: carbohydrates, fats (minimal) A: none Small Intestine Function - correct answer ✔✔M: mixing and propulsion, mostly by segmentation S: enzymes, HCO3-, bile, mucus, CCK, secretin, GIP, etc. D: carbs, fats, polypeptides, nucleic acids A: peptides, amino acids, glucose, fructose, fats, water, ions, minerals, vitamins
Large Intestine Function - correct answer ✔✔M: segmental mixing, mass movement for propulsion S: mucus D: none A: ions, water, minerals, vitamins, small organic molecules Saliva Functions - correct answer ✔✔secreted under autonomic control softens and lubricates food digests with salivary amylase, some lipase antimicrobial: lysozyme, immunoglobins Swallowing Reflex Initiation and Mediation - correct answer ✔✔integrated in medulla mediated by: -sensory afferents in cranial nerve IX (9) -somatic motor neurons -autonomic neurons Swallowing Reflex Steps (3) - correct answer ✔✔1) Swallowing reflex - triggered by tongue pushing bolus against soft palate and back of mouth
- breathing inhibited as bolus passes closed airway - epiglottis folds down - upper esophageal sphincter relaxes
3 Functions of Stomach - correct answer ✔✔1) storage
- digestion -mechanical and chemical processing into chyme -secretions (enzymes, acid, hormones)
- protection -acid: against microbes -mucus bicarbonate barrier: self-protection Mucus - correct answer ✔✔mucus neck cell stimulus for release -tonic secretion -with irritation of mucosa function of secretion -physical barrier between lumen and epithelium Bicarbonate - correct answer ✔✔mucus neck cell Stimulus for release -secreted with mucus function -buffers gastric acid to prevent epithelial damage Gastric Acid (HCl) - correct answer ✔✔parietal cells
stimulus for release -acetylcholine -gastrin -histamine function -activates pepsin -kills bacteria Intrinsic Factor - correct answer ✔✔parietal cells stimulus for release -acetylcholine -gastrin -histamine function -complexes with vitamin B12 to permit absorption Histamine - correct answer ✔✔enterochromaffin-like cell stimulus for release -acetylcholine -gastrin function -stimulates gastric acid (HCl) secretion Pepsin(ogen) - correct answer ✔✔chief cells
-peptides -amino acids function -stimulates gastric acid (HCl) secretion Mucous neck cell - correct answer ✔✔secretes mucus and bicarbonate Parietal cells secrete - correct answer ✔✔gastric acid (HCl) and intrinsic factor Enterochromaffin-like cell - correct answer ✔✔secretes histamine Chief cells - correct answer ✔✔secrete pepsin and gastric lipase D cells - correct answer ✔✔secrete somatostatin G cells - correct answer ✔✔secrete gastrin Peptic Ulcer - correct answer ✔✔acid and pepsin damage the mucosal surface creates holes that extend into submucosa and muscularis layers results from breakdown of mucus-bicarb barrier Prevention/Treatment of Peptic Ulcers - correct answer ✔✔1) antacids - neutralize gastric acid
- H2 receptor antagonists - block histamine action (to prevent gastric acid release)
- proton pump inhibitors - block H+/K+ ATPase
