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Flashcards in Gastrointestinal Physiology - Theoretical Questions Deck (127)
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What are MMCs?

Migrating motor complexes : while fasting Motilin is released and sets the contractions of colon to a rate of 1 per 90 minutes.


Give examples for Local Peristaltic reflexes in the GI tract? What is common for all?

Gasrto-enteric, Gastro-Ileal, Gastro-colic, Dudenocolic, Enterogastric, Colocolic, Rectocolic.
First name senses the stimulus (Stretch/pH/Content) and later sends with AND/ENS/Hormone the signal to the second to Contract/Relax.


Salivary glands - Daily production of Saliva? Sites of Production?

1 Liter from Parotid, Submandibular and Sublingual glands


What is the contractile unit around the salivary glands acini?

Myoepithelial cells


What are the components of human Saliva?

Lingual Lipase, Amylase, and Hypotonic/Isotonic solution similar to plasma (Depends on eating/fasting states).


What is the First step of Sequential secretion ?

Acinus produces Isotonic secretion with plasma with NCCK, Na/K ATPase and CFTER pumps.


What is the Second step of Sequential secretion ?

Ductal cells increase Potassium and Bicarbonate and Decrease Sodium and Chloride ion concentrations in Saliva turning it to Hyposmolar solution with Higher pH.


What happens to the saliva during eating? and what happens while not eating?

Eating - Flow Rate ↑ - Ion exchange in the ductal cells↓ :
Saliva becomes Isosmotic
Not Eating - Flow Rate ↓ - Ion exchange in the ductal cells↑ :
Saliva becomes Hyposmotic


What are the transmembrane proteins found on the ductal cells Apical surface?

Bicarbonate/Cl Exchanger, H/Na Exchanger and K/H Exchanger.


What is the Unique feature of Salivary glands regulation? (Not like other GI parts)

Salivary glands regulation is purely neurogenic and Both Sym and Para INCREASE the saliva production.


Salivary: What is the Ion secretion that is independent from the Flow rate effects on secretion? What regulates it?

Bicarbonate secretion is regulated selectively by Parasympathetic innervation


What is the effect of Parasympathetic regulation on saliva ?

Smelling or tasting causes nerves to release :Ach - M3(Gq) - Calcium signal causes fluid and enzyme↑
and VIP - Gs - Vasodilation on Glands arterioles.
Ultimately Increasing secretion.


What is the effect of Sympathetic regulation on saliva ?

Norepinephrine - Beta-2 receptors - PKA - Mucin↑
Ultimately Increasing secretion.


What are the components of Gastric Juice? which are the cells secreting them?

Chief cells - Pepsinogen
Parietal cells -HCl, Intrinsic Factor
Mucus cells - Mucus.


Mechanism of Parietal cells secretion:
Transmembrane proteins on the Apical surface

H-K PUMP , K and Cl channels


Mechanism of Parietal cells secretion:
Transmembrane proteins on the Basal surface?
What is the enzyme needed here?

Na/K ATPase, Bicarbonate/Cl exchanger
Carbonic anhydrase allows for diffused CO2 and H2O to turn into Carbonic Acid and later form Bicarbonate and Proton.


What happens to the Bicarbonate released back to blood Normally? and in Vomiting?

This Bicarbonate travels in blood to reach the pancreas and to be released to Small intestines, in vomiting since there is no stimulation of pancreas and no pH drop in Small intestine the Bicarbonate remains in blood - Metabolic alkalosis!


Stimulators of HCl secretion in Parietal cells?
Drugs inhibiting?

Ach (Gq) - Atropine inhibits
Histamine (GS) - Cetamidine inhibits
Gastrin (Gq)


What are the inhibitors of HCl secretion in Parietal cells?
Indirectly as well..

SST and Prostaglandins (both Gi)
SST also blocks G cells and ECL cells from secreting Gastrin and Histamine respectively


What are the 3 stages of HCl secretion stimulation?
What are their relative proportions?

Cephalic (40%): Smell/Taste - Dorsal Vagal Nucleus - Ach
Gastric (50%): Destination/Protein - ENS/Vagovagal/Gastrin
Intestinal (10%)l: Gastrin


What are the Pancreatic enzymes? What do they digest?

1)Carbohydrates - Amylase
2)Proteins - Trypsin, Chymotrypsin, Carboxypeptidase, Elastase
3)Lipids - Lipase and Colipase


What is changing the amount of bicarbonate amount in the pancreatic secretion?

Bicarbonate/Cl exchanger
it is more active in high flow rate (to intercept stomach acid arrival to duodenum after eating)


Phases of pancreatic secretion:
What happens in each stage?

Cephalic - Smell/Taste - Vagus - Ach - Acinar secretion
Gastric - Distention - Vagus - Ach - Acinar secretion
Intestinal phase (80%) - I cells sensing AA- CCK secretion + GI chemoreceptors - Vagus - Ach


How is the Intestinal phase of the Pancreatic Secretion allows for an Increase in aqueous fluid and Bicarbonate secretion?

S cells in the Duodenum senses Protons from gastric chyme. These will release Secretin a GI hormone that will stimulate the Ductal cells to release the Bicarbonate and Aqueous solution.


What stops the pancreatic secretion?

Ileum and Colon release (when getting chyme) the Neuropeptide Y


What is the gallbladder functions?

Stores, Concentrates and Releases Bile


How is Bile being concentrated in the gallbladder?

Standing gradient osmotic mechanism:
NaCl reabsorption to blood that causes osmosis and remaining lipid molecules are now able to form Micelles.


What is the composition of Bile?

Bile salts, Phospholipids, Cholesterol and Bilirubin (Pigmentation)


Where is bile formed? How does it get to the gallbladder?

Cholesterol filtered from discontinuous capillaries into the hepatic spaces of Disse. Then in the hepatocytes Primary Bile acids from and NTCP and BSEP move them out of the hepatocytes canaliculi to the common hepatic and cystic duct to GB.


What are the primary bile acids? what are the secondary bile acids and where do they form?

Primary - Cholic Acid and Chenodeoxycholic acid
Secondary - Deoxycholic acid and Lithocholic acid.
Secondary Bile acids are formed from the primary ones by Bacteria in the gut (7-dehydroxylases)