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57 Cards in this Set
- Front
- Back
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What is the function of the GI system?
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to transfer nutrients, water, and electrolytes from the external to the internal environment of the body.
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What is external and what is internal?
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External: lumen of the GI tract.
Internal: absorbed side |
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What 4 processes take place in the GI system?
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1. Motility
2. Secretion 3. Digestion 4. Absorption |
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What are two types of motility in the GI system?
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1. Propulsive movements - push GI contents FORWARD.
2. Mixing movements - mixes food with enzymes and contact w/ wall |
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What secretion occurs in the GI tract?
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Secretion of Exocrine gland substances into the tract.
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What is digested in the GI tract?
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1. Protein
2. Fat 3. Carbs |
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What direction does absorption occur?
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From the lumen of the tract to the body.
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What 8 structures constitute the gi tract?
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1. Mouth 2. Esophagus 3. Stomach
4. Duodenum 5. Jejunum 6. Ileum 7. Lg intestine 8. Annus |
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What makes up the small intestine?
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the Duodenum/jejunum/ileum
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What three exocrine glands secrete into the tract?
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1. Salivary glands (into mouth)
2. Liver (into duodenum) 3. Pancreas (into duoden.) |
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-What 3 cell types are in the GI tract endothelial lining?<br />-What does each cell type secrete?
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1. Endocrine - hormones from stomach to blood
2. Exocrine - enzymes/HCl into stomach lumen 4. Mucus - right into lumen |
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How are exocrine glands structured for the GI tract?
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As folds of the epithelial layer, shaped into pouches.
-Not seperate organs! |
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What is the purpose of the Mucus secreted into the GI tract?
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It gives a protective slimy coating to make food move through more easily.
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What makes up the 5 layers around the stomach? (from lumen moving out)
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1. Submucus nerve plexus
2. Circular muscle 3. Myenteric nerve plexus 4. Longitudinal muscle<br 5. Serosa |
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Of the intestinal lining layers, what are we interested in?
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Nerves and muscles b/c they allow for motility.
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What is the serosa essentially?
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Connective tissue.
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What is another name for the enteric nervous system?
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"little brain in the gut"
-ENS |
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What 2 layers make up the enteric nervous system?
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1. Submucus nerve plexus
2. Myenteric nere plexus |
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What are some properties of the Enteric NS?
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-Unique - not found anywhere else in the body.
-Has as many neurons as the spinal cord. -Intrinsic to the GI tract - reflexes occur entirely w/in. -Uses many different NTs |
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What muscles does the ENS control?
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smooth muscle fibers of longitudinal/circular layers.
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Do the NT in the ENS depolarize or hyperpolarize?
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BOTH
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Where are the neuromuscular junctions located in the ENS?
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Nowhere in particular; Synaptic vesicles containing NTs are in VARICOSITIES.
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What is a Varicosity?
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bulby-type thing that holds synpatic vesicles of neurotransmitters. When activated, releases NT.
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What happens when an action potential crosses a varicosity?
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1. Synaptic vesicles release NT
2. NT binds smooth muscle receptor 3. NT acts in appropriate manner |
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In the ENS what happens if a NT -Depolarizes
-Hyperpolarizes |
Depol: Ca2+ influx increases into the smooth muscle cell and increases contraction strength.
Hyper: Ca2+ influx decreases |
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What are the actions of AcH and Norepi on the ENS?
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AcH activates smooth muscle and causes contraction.
Norepi relaxes smooth muscle and causes hyperpolarization. |
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Which nervous systems release AcH and Norepi?
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AcH: parasympathetic - either Enteric or PNS.
Norepi: sympathetic - either enteric or SNS. |
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Through what type of action does the Nervous system control the GI tract?
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REFLEX ARCS
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What are the 3 components in a reflex arc?
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1. Receptors
2. Integrator 3. Effectors |
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What are the 3 Receptors in the GI reflex arc?
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1. Osmoreceptors
2. Mechanoreceptors 3. Chemoreceptors |
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What are the Integrators in the GI reflex arc?
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1. CNS/Brain/Spinal cord
2. Enteric nervous system -That's what makes it special - it has TWO integrators! |
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What are the 3 Effectors in the GI tract Reflex arc?
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1. Smooth muscle
2. Endocrine cells 3. Exocrine cells |
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Where do receptors send information, via what structure?
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1. To CNS via vagus nerve
2. To ENS via local afferents. |
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How does the CNS integrator send information for an effect?
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1. To the ENS integrator via sympathetic parasympathetic nerves.
2. Directly to the effectors via the autonomic NS. |
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How does the ENS integrator send info for an effect?
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Via local efferents to the effectors.
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What denotes a reflex that occurs entirely within the GI tract w/out consulting the CNS?
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Short reflex arc.
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When the CNS sends orders for an effect, what 2 autonomic components are used, and what is each effect?
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1. Sympathetic NS; inhibits GI action.
2. Parasymp NS; stimulates GI action. |
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What are the 4 hormones of the GI tract?
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1. Gastrin
2. Secretin 3. Cholecystokinin (CCK) 4. Gastric inhibitory peptide (GIP) |
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What is the source of Gastrin?
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The lining of the stomach; it is secreted into the blood around the stomach.
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What stimulates the release of Gastrin?
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Protein in food.
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What is the 2 functions of Gastrin?
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1. Stimulates gastric motility and secretion of HCl into lumen.
2. Stimulates Gastroileal reflex |
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What are 3 effects of stimulating gastric motility and secretion?
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1. More Hcl in stomach
2. Increased mixing 3. Increased rate of emptying stomach contents. |
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What happens during the Gastroileal reflex?
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1. Food in stomach
2. Increased ileal motility (at the end of the sm. intestine) 3. Ileacecal sphincter relaxes 4. Food moves from sm to lg intestine 5. Defacation. |
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So in a nutshell: what's the general function of Gastrin?
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To stimulate the stomach to digest food and clear space in the intestines - what oatmeal does in the morning.
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What is the source of secretin?
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The duodenum walls
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What stimulates secretin release?
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Acid in the duodenum
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What is Secretin's function?
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To decrease acid secretion from the stomach, and inhibit gastric motility.
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What are the 2 ways that Secretin performs its function?
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1. Slows the rate of acid leaving the stomach.
2. Stimulates release of Bicarb from the pancreas/liver into duodenum to neutralize acid. |
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What is the general function of secretin in a nutshell?
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To slow acid entering duodenum and also neutralize it.
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What is the source of CCK?
What stimulates it? What is its general function? |
1. Duodenum
2. Fat and protein in duodenum 3. To inhibit gastric motility and secretion. |
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How specifically does CCK work?
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1. Stimulates pancreatic/liver enzyme secretion into duodenum
2. Stimulates gall bladder contraction |
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In general how does CCK work?
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Slows rate of food entry into duodenum; adds enzymes to break down fat and protein.
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What is the source of GIP?
What stimulates it? What is its general function? |
1. Duodenum
2. Gluocse in duodenum 3. To inhibit gastric motility and secretion |
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How specifically does GIP work?
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Stimulates insulin production and secretion
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In general, how does CCK work?
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1. Slows the rate of glucose entering the duodenum
2. Prepares for glucose load in the blood. |
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Which 3 gastric hormones are very similar and which is the oddball?
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3 similar = Secretin, CCK, GIP; they all INHIBIT
Oddball = Gastrin; stimulates. |
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What are the three similar hormones called collectively?
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Enterogastrones
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