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88 Cards in this Set

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  • Back
What are the 3 major characteristics of GI smooth muscle motility?
1. Smooth muscle is primarily single unit
2. Pacemaker cells allow for spontaneous depolarization.
3. Areas of hyperpolarization stop waves of depolarization.
What makes single unit smooth muscle unified?
Gap junctions - they couple the cells electronically.
What controls the stopping of depolarization?
Norepinephrine - released over areas where hyperpolarization is intended to occur.
What controls the release of norepinephrine?
What are the 3 patterns of "GI motor behavior?"
1. Peristalsis
2. Mixing
3. Sphincters
What type of movement is caused by peristalsis?
Propulsive - it pushes the GI contents forward
In what 2 structures does peristalsis occur?
1. Esophagus
2. Intestines
What 2 types of muscular contraction allows for peristaltic movement?
1. Circular muscle Contraction
2. Longitudinal musc contraction

-But in adjacent segments.
What are the 2 adjacent segments in peristaltic muscle named?
What muscle is contracting in each?
1. Propulsive segment - circular muscle contracts here
2. Receiving segment - longitnl. muscle contracts here.
What does Circular contraction do?
Decreases the diameter of the GI tract and causes forward movement.
What does longitudinal contraction do?
Shortens the GI tract and increases the diameter.
How does vomitting occur?
By reverse peristalsis - the small intestine forces contents to stomach, then Ab contraction forces food out.
If Longitudnl muscle contracts, what does circular do?

If circular muscle contracts, what does longitud do?
-is inhibited.

Where does MIXING motor muscle occur?
in the intestines - accounts for their wound up, bumpy, messiness.
What are the segments in mixing?
-Propulsive - bidirectional
-Receiving - where mixing occurs

-They flip back and forth, take turns being each other.
If food is being pushed back and frth w/out forward movement, how does it move thru intestines?
Usually there is a combination of mixing and peristalsis.
What are Sphincters?
Muscles that close off the GI tract.
What are the 2 types of sphincters?
1. Involuntary (smooth muscle)
2. Voluntary (skeletal muscle)
What 4 things must we consider regarding the mouth and esophagus?
1. Motility
2. Secretions
3. Secretion regulation
4. Functions of saliva
In what state are the upper and lower esophageal sphincters normally?
-upper to prevent air entry into the esophagus
-lower to prevent acid reflux
What 2 types of actions occur in swallowing?
1. Voluntary
2. Involuntary
What does voluntary action accomplish re: motility during swallowing?
it pushes saliva to the back of the mouth.
What does Involuntary action accomplish/cause?
1. Upper sphincter relax/opens
2. Primary peristalsis in esophagus
3. Lower sphincter relax/food enters stomach
What triggers 2ndary peristalsis?
Food remaining in the esophagus after swallowing.
What are the main secretions in the mouth and esophagus?
From the salivary glands in the mouth.
Where is saliva formed, and what three cell types add to it?
-In the saliva glands.
1. Serous cells
2. Myoepithelial cells
3. Mucus cells
What is the function of serous cells?
Line salivary gland; contain zymogen granule vesicles.
Zymogen grans release amylase
what is the function of amylase?
breaks down carbs
What do Myoepithelial cells do?
Contract and force out saliva from the gland and increase its flow.
What do mucus cells do?
Secrete mucus into saliva.
Is Saliva just saliva, or can it be altered? How?
It can be altered - as it flows through the duct, duct cells add HCO3- for acid neutralization, and remove some Na and Cl so the saliva is hypotonic.
What 2 things regulate saliva secretion?

Which is more important?
-PNS -> the main actor
How does SympNS control salivary secretion?
It causes a small transient increase in salivary flow.
How does ParaNS control salivary secretion?
It causes a LARGE increase in salivary flow!
What stimulates PNS activation of salivary flow, and how does it work (2 things)?
Stimuli: thinking/smelling, tasting/chewing. Result:
1. Vasodilation of vessels near salivary glands.
2. Increased capillary permeability so more fluid enters saliva glands.
What are the 3 enzymes in saliva?
1. Salivary amylase
2. Lingual lipase
3. Mucins
What does Salivary amylase do? What's another name for it?
What happens to it in the stomach?
Ptyalin; begins carb breakdown but is inactivated in the stomach by acid.
What does lingual lipase do? Does it work very well?
Begins fat breakdown; no - there are no bile salts around to emulsify the fats.
What are mucins?
Glycoproteins found in mucus.
So what are the 5 functions of saliva?
1. Begin carb breakdown
2. Begin fat breakdown
3. Put mucus in mixture
4. Solvent for tasting
5. Aid in speach
What are the anatomical components of the stomach?
1. Fundus/cardia
2. Body
3. Antrum
4. Pyloric sphincter
5. Pylorus
then the duodenum.
What is the function of
Fundus/body are for storage.
Antrum is for mixing - lots of smooth muscle here (why its smaller)
What type of motility occurs in the stomach?
Mixing, which increases the rate of stomach emptying.
What stimulates mixing?
Gastrin and the PARA NS
What type of meal has the slowest rate of emptying?
A fatty meal - it increases CCK which inhibits gastric motility and secretion.
What is the most potent inhibitor of stomach motility?
What is "Receptive Relaxation"?
Phenomenon where a full stomach is relaxed, and an empty stomach contracts.
What stimulates receptive relaxation?
The full stomach stimulates the PARASNS to stimulate the ENS, which inhibits stomach smooth muscle.
What 4 things get secreted into the stomach? From which glands?
1. Mucus - oxyntic gland
2. HCl - oxyntic gland
3. Pepsinogen - oxyntic gland
4. Gastrin - pyloric gland
What secretes mucus, and why?
Mucus cells; to protect the stomach from acid.
What do the Parietal cells secrete?
HCl and intrinsic factor
what do Chief cells contain?
Zymogen granules; which secrete pepsinogen.
What does pepsinogen do, and why does it have to be in granules?
Breaks down protein; in granules to protect the cells.
What does the Pyloric gland contain?
G cells, which secrete Gastrin (a hormone!!)
What is the oxyntic gland structurally?
A folding of the stomach that contains exocrine glands.
What is the mechanism of HCl secretion from parietal cells?
1. CO2 diffuses in parietal cells from the blood.
2. CO2 combines w/ H2O = H+ and HCO3-
3. H+ goes to stomach
4. HCO3- goes back to blood in exchange for CL-.
5. Cl- diffuses to stomach.
What is "Alkaline Tide"?
The increase in pH of blood passing the stomach because a lot of bicarb enters in exchange for Cl-.
What are the 3 phases of gastric secretions?
1. Cephalic
2. Gastric
3. Intestinal
What 3 things regulate gastric secretions?
1. Autonomic NS
2. Enteric NS
3. Hormones
When does the cephalic phase occur?
Before food enters the stomach; while thinking/smelling/tasting, chewing..
What does the cephalic phase stimulate?
Increase in HCl and pepsinogen secretions.
When does the Gastric phase occur?
When food is in the stomach.
What does the gastric phase stimulate?
Increase in HCl, and Pepsinogen secretions. BY THE ACTION OF GASTRIN.
When does the intestinal phase occur?
When food is in the duodenum
What does the intestinal phase stimulate?
Decrease in HCl and Pepsinogen secretions. BY THE ACTION OF ENTEROGASTRONES.
When does Gastrin work?
When do CCK/Secretin/GIP work?
-During GASTRIC phase.
-During INTESTINAL phase.
How many functions of gastric juice are there?
3 :) keep going you can do it.
What functions are gastric juice involved with?
1. Stimulate Digestion
2. Bactericidal action
3. Supply of intrinsic factor
How does gastric juice stim digestion?
It has HCl; HCl catalyzes activation of pepsinogen to pepsin; pepsin breaks down proteins.
Does HCl control the continuous activation of pepsin?
No; only the beginning; then by autocatalysis pepsin activates formation of itself.
How does gastric juice have bactericidal action?
The low ph kills most ingested bacteria
What bacteria does gastric juice not kill?
Helicobacter pylori - often a cause of peptic ulcers.
How does gastric juice supply intrinsic factor?
The parietal cells secrete it, and it allows for Vit B12 absorption/ RBC production.
What important juice does the liver secrete?
Where is bile stored and concentrated?
In the gallbladder.
What hormone stimulates release of bile again?
Cholecystikinin - causes gall bladder contraction
What is Bile made up of? (three things)
1. HCO3-
2. Bilirubin
3. Bile salts
What are bile salts and what do they do?
Derived from cholesterol, they emulsify fat.
of the stuff in the duodenum, what gets absorbed into the bloodstream and transported to the liver?
only glucose and protein; not fat.
What happens to glucose at the liver?
-If high serum glucose, makes glycogen.
-If low serum glucose, keep it in the blood.
What happens to protein at the liver?
1. May convert to other amino acids
2. Make plasma proteins
3. Convert to glucose via gluconeogenesis.
4. Remain in blood.
Bile salts have 2 distinct regions; what are they?
1. Cholesterol-derived region which is nonpolar, lipophilic.
2. Amino acid chain which is polar, neg charged, lipophobic.
Which region of the bile salt is stuck in the fat droplet?
Which is in the water?
cholesterol region - lipid

amino acid chain - water
How do large fat droplets get broken into smaller ones?
What happens to small fat droplets?
Bile salts stick their cholesterol tails into them.
How do bile salts function as emulsifiers?
Their negative charges surrounding the fat repel each other and prevent reformation of the large fat droplets.
What 2 things DONT bile salts do?
-Don't break apart large fat droplets
-Don't break down fat
What are Micelles composed of?
1. Fat
2. Bile salts
3. Cholesterol
4. Fat soluble vitamins A/D/E