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57 Cards in this Set

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  • Back
What is the function of the GI system?
to transfer nutrients, water, and electrolytes from the external to the internal environment of the body.
What is external and what is internal?
External: lumen of the GI tract.
Internal: absorbed side
What 4 processes take place in the GI system?
1. Motility
2. Secretion
3. Digestion
4. Absorption
What are two types of motility in the GI system?
1. Propulsive movements - push GI contents FORWARD.
2. Mixing movements - mixes food with enzymes and contact w/ wall
What secretion occurs in the GI tract?
Secretion of Exocrine gland substances into the tract.
What is digested in the GI tract?
1. Protein
2. Fat
3. Carbs
What direction does absorption occur?
From the lumen of the tract to the body.
What 8 structures constitute the gi tract?
1. Mouth 2. Esophagus 3. Stomach
4. Duodenum 5. Jejunum 6. Ileum
7. Lg intestine 8. Annus
What makes up the small intestine?
the Duodenum/jejunum/ileum
What three exocrine glands secrete into the tract?
1. Salivary glands (into mouth)
2. Liver (into duodenum)
3. Pancreas (into duoden.)
-What 3 cell types are in the GI tract endothelial lining?<br />-What does each cell type secrete?
1. Endocrine - hormones from stomach to blood
2. Exocrine - enzymes/HCl into stomach lumen
4. Mucus - right into lumen
How are exocrine glands structured for the GI tract?
As folds of the epithelial layer, shaped into pouches.
-Not seperate organs!
What is the purpose of the Mucus secreted into the GI tract?
It gives a protective slimy coating to make food move through more easily.
What makes up the 5 layers around the stomach? (from lumen moving out)
1. Submucus nerve plexus
2. Circular muscle
3. Myenteric nerve plexus
4. Longitudinal muscle<br
5. Serosa
Of the intestinal lining layers, what are we interested in?
Nerves and muscles b/c they allow for motility.
What is the serosa essentially?
Connective tissue.
What is another name for the enteric nervous system?
"little brain in the gut"

What 2 layers make up the enteric nervous system?
1. Submucus nerve plexus
2. Myenteric nere plexus
What are some properties of the Enteric NS?
-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
What muscles does the ENS control?
smooth muscle fibers of longitudinal/circular layers.
Do the NT in the ENS depolarize or hyperpolarize?
Where are the neuromuscular junctions located in the ENS?
Nowhere in particular; Synaptic vesicles containing NTs are in VARICOSITIES.
What is a Varicosity?
bulby-type thing that holds synpatic vesicles of neurotransmitters. When activated, releases NT.
What happens when an action potential crosses a varicosity?
1. Synaptic vesicles release NT
2. NT binds smooth muscle receptor
3. NT acts in appropriate manner
In the ENS what happens if a NT -Depolarizes
Depol: Ca2+ influx increases into the smooth muscle cell and increases contraction strength.
Hyper: Ca2+ influx decreases
What are the actions of AcH and Norepi on the ENS?
AcH activates smooth muscle and causes contraction.

Norepi relaxes smooth muscle and causes hyperpolarization.
Which nervous systems release AcH and Norepi?
AcH: parasympathetic - either Enteric or PNS.

Norepi: sympathetic - either enteric or SNS.
Through what type of action does the Nervous system control the GI tract?
What are the 3 components in a reflex arc?
1. Receptors
2. Integrator
3. Effectors
What are the 3 Receptors in the GI reflex arc?
1. Osmoreceptors
2. Mechanoreceptors
3. Chemoreceptors
What are the Integrators in the GI reflex arc?
1. CNS/Brain/Spinal cord
2. Enteric nervous system

-That's what makes it special - it has TWO integrators!
What are the 3 Effectors in the GI tract Reflex arc?
1. Smooth muscle
2. Endocrine cells
3. Exocrine cells
Where do receptors send information, via what structure?
1. To CNS via vagus nerve
2. To ENS via local afferents.
How does the CNS integrator send information for an effect?
1. To the ENS integrator via sympathetic parasympathetic nerves.
2. Directly to the effectors via the autonomic NS.
How does the ENS integrator send info for an effect?
Via local efferents to the effectors.
What denotes a reflex that occurs entirely within the GI tract w/out consulting the CNS?
Short reflex arc.
When the CNS sends orders for an effect, what 2 autonomic components are used, and what is each effect?
1. Sympathetic NS; inhibits GI action.

2. Parasymp NS; stimulates GI action.
What are the 4 hormones of the GI tract?
1. Gastrin
2. Secretin
3. Cholecystokinin (CCK)
4. Gastric inhibitory peptide (GIP)
What is the source of Gastrin?
The lining of the stomach; it is secreted into the blood around the stomach.
What stimulates the release of Gastrin?
Protein in food.
What is the 2 functions of Gastrin?
1. Stimulates gastric motility and secretion of HCl into lumen.
2. Stimulates Gastroileal reflex
What are 3 effects of stimulating gastric motility and secretion?
1. More Hcl in stomach
2. Increased mixing
3. Increased rate of emptying stomach contents.
What happens during the Gastroileal reflex?
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.
So in a nutshell: what's the general function of Gastrin?
To stimulate the stomach to digest food and clear space in the intestines - what oatmeal does in the morning.
What is the source of secretin?
The duodenum walls
What stimulates secretin release?
Acid in the duodenum
What is Secretin's function?
To decrease acid secretion from the stomach, and inhibit gastric motility.
What are the 2 ways that Secretin performs its function?
1. Slows the rate of acid leaving the stomach.
2. Stimulates release of Bicarb from the pancreas/liver into duodenum to neutralize acid.
What is the general function of secretin in a nutshell?
To slow acid entering duodenum and also neutralize it.
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.
How specifically does CCK work?
1. Stimulates pancreatic/liver enzyme secretion into duodenum
2. Stimulates gall bladder contraction
In general how does CCK work?
Slows rate of food entry into duodenum; adds enzymes to break down fat and protein.
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
How specifically does GIP work?
Stimulates insulin production and secretion
In general, how does CCK work?
1. Slows the rate of glucose entering the duodenum
2. Prepares for glucose load in the blood.
Which 3 gastric hormones are very similar and which is the oddball?
3 similar = Secretin, CCK, GIP; they all INHIBIT

Oddball = Gastrin; stimulates.
What are the three similar hormones called collectively?