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46 Cards in this Set

  • Front
  • Back
How are gastrin and CCK related?
they have the same 5 AA's in their C peptide end
2 ways in which parietal cells respond to gastrin
1. they grow more
2. they secrete more HCl
Where is meissner's plexus and aurbauch's plexus relative to their respective layers?
meissner's- at the bottom of the submucosa

auurbauch's- in between the circular and longitudinal layers
What spinal levels do the enteric S NS originate from?
T8-L2
What circulation do GI hormones go through?
the hepatic portal circulation
What are the two types of gastrin that we have?

WHich one is released in response to a meal?

WHat are two of the most potent AA's triggering gastrin release>
There is little gastrin which is 17 amino acid long and a gastrin which is 34 amino acid.

Little gastrin is treated in response to a meal

Tryptophan and phenylalanine are the best triggers for little gastrin release
Will atblropine ock gastrin release? Why or why not?
No because the vagal effect on gastrin release is mediated through GRP (gastrin releasing peptide)
What cell are cancerous in a gastrinoma?
Pancreatic cells that aren't beta
How many amino acids the CCK have?

What part of it is biologically active? Implications?
33 amino acids with the last 7 on the C-terminal being active

This means that CCK can bind to gastrin receptors, but gastrin cannot bind to CCK receptors
Do triglyceride directly stimulates the release of CCK?
Only fatty acids and monoglyceride and amino acids do because they can actually get into the intestinal cell
What cells are CCK released from?
The I cells of the duodenum and jejunum
What hormones stimulate the growth of the exocrine pancreas? How do you know?
CCK and secretin because they trigger exocrine product release so they would want there to be more cells in the pancreas just like gastrin would want there to be more cells in the stomach
How many amino acids are in secretin? How many of these are the same as in glucagon?
27 amino acids, 14 of which are the same in glucagon
What cells in what part of the intestines secrete secretin?
The S cells of the duodenum
What are the 2 stimuli for secretin?
H+ and fatty acids in the duodenum
Is giving oral glucose or IV glucose better at stimulating insulin? Why?
Oral glucose because that's capable of stimulating GIP as well, which will increase the insulin release
How does the vagus nerve trigger the parietal cell versus the G cell?
It triggers parietal cell directly with ACh and the G cell indirectly with GRP
What triggers the release of the VIP?

What inhibits it?
It all neuronal

Vagal stimulation (extrinsic) and distention (intrinsic) stimulate it

Sympathetic stimulation inhibits it
Of all the intestinal hormones, which one is different in where it is secreted? How so?

How can you remember this?
Secretin is only released in the duodenum whereas CCK and GIP are released in the duodenum and the jejunum

Stomach H+ is neutralized very quickly so there is no use for secretin later on
What is another name for GRP?
bombesin
What category of molecules are enkephalins in?

What are the released from in the intestines? Give 2 examples of enkephalins
They are opioids that are secreted from the intrinsic nerves of both G.I. plexuses

some examples are met-enkephalin and leu-enkephalin
What are 2 functions of enkephalins in the GIT?
1. They stimulate contraction of all the sphincters that are not the 1st and the last
2. They inhibit intestinal secretion of fluid and electrolytes

Basically, they stop the passage of intestinal contents
What condition are opioids very good at treating in the G.I. tract?
diarrhea
What is the orad stomach?
Orad stomach - Fundus and proximal body
What is the difference between phasic and tonic contractions?
phasic- contracts and relax with oscillations ofmembrane potantial

tonic- typicaly contracted unless specifically told to relax
What things in the G.I. tract are tonic contracted?
Basically all of the sphincters and the orad stomach
How do you know that the orad stomach is tonicly contracted?
Where it can expand A LOT
Is it enough that slow waves reached a peak in order for the G.I. tract to contract?
no,You must have action potentials on top of the slow wave peaks in order for contraction to happen.

It is like standing on the shoulders of giants
So if the depolarization in slow waves don't cause action potentials, what do they do?
They just make it more likely for action potentials to happen
How can you change the frequency of slow waves?
You can't
So what are we changing with neuronal and hormonal input to change the rate of contraction?
We are changing the number of action potentials superimposed on the slow waves
Describe what contractions look like in terms of frequency in the G.I. tract.

Do the stomach for example
There are 3 slow waves every minute, so there could be a bundle of 5 contractions 3 times a minute
What is the pressure in the esophagus equal to? Why?
Intrathoracic pressure because of the same reason as the lung
What kind of stimulation creates more vs less action potentials on top of the slow waves?
ACh puts more in, Sympathetic stimulation puts less
What is the MAIN mediator of the gastroileal reflex?

A secondary, not as important mediator?
extrinsic vagal stimulation in response to distension in the stomach

gastrin
Where does the majority of water get reabsorbed in the colon?
in the early colon
What reflex produces the urge to defecate? What is contracting/relaxing?
the recosphincteric reflex initiated by distension in the rectum

the rectum contracts and the internal sphincter relaxes
In a normal person, when is the rectosphincteric reflex initiated?
when the rectum is 25% full
What is it called when you expire against a closed glottis?
the valsalva maneuver (like in trying to poop)
What do you have to be careful of when you do the valsalva maneuver?
hypertension and aneurysm
What is the gastrocolic reflex?
the increase of mass movements in the colon is response to food in the stomach
WHat are the two components of the gastrocolic reflex?

What mediates each component? Which is faster? Which is more important?
there is a fast and more powerful neuronal component mediated by the PS NS

a slower, hormonal component mediated by CCK and gastrin
What are 3 other structures in the brain that advise the vomiting center besides the CTZ?
1. cerebellum/vestibular nuclei
2. cortex/limbic system
3. NTS (sensory from throat for gag reflex)
What are the salivary amylase and lipase specifically called?
a-amylase- ptyalin
lingual lipase
What is the main signal mediating LES and orad stomach relaxation?
VIP!
What are the signals mediating peristalis front relaxation?
NO and VIP