Physiology Flashcards
(37 cards)
What 3 secretagogues induce HCl production?
How do they increase the HCl production?
What cell do they activate?
Think of witch melting in Wizard of Oz - like melting in acid - HCl = HAG
H = histamine
A = ACh
G = gastrin
Cause an increase in proton pumps
Parietal cells activated
Specifically where in the stomach is HCl produced and what enzyme is involved?
In gastric pit lumen outside parietal cells
H+/K+/ATPase pump
Name the 3 phases of gastrin secretion
Cephalic - before food has even reached stomach
Gastric - distension increases HCl production
Intestinal - once left stomach
CGI - think of a CGI stomach pumping out acids
During the cephalic phase of gastric secretion what causes an increase in HCl production?
Vagus nerve stimulates production of HAG
Histamine
ACh
Gastrin
Describe what happens to food when it enters the stomach in terms of movement through the stomach?
Tonic waves push food towards antrum
Slow antral waves move food towards pyloric sphincter where when it is too large - RETROPULSION
What part of brain controls appetite? What nerves stimulates appetite and what does it act on? Same for inhibits appetite?
Hypothalamus
Stimulates - orexigenic neurons - lateral hypothalamic
Inhibits - anorexiogenic neurons -ventromedial nuclei
What part of brain controls vomiting?
Medulla
What three secretagoues also have an impact on hunger. What cells produce them and where are these cells found?
Leptin inhibits - adipose cells - adipose tissue
Ghrelin stimulates - Gr cells - gastric antrum and small bowel (hungry work retropulsion)
CCK inhibits - I cells - duodenum and jejunum -
How does small intestine deal with highly acidic chyme?
Duodenum contains Brunner’s Glands which release an alkaline substance to neutralise
What is a TGA?
Triglcyeride - consumed from fat
Three glycerides = 3x glycerol + FA chains
What enzyme hydrolyses emulsions into free fatty acids? What releases it and what induces the organ to release it?
TGA-lipase
Released by panceras which is initated by release of CCK from I cells (duodenum and jejunum)
What is emulsion?
Combination of fat droplets and bile salts (produced by liver)
When a micelle reaches an enterocyte then what happens? How do lipids reach blood stream?
Release FAs
Small chain FAs - diffuse through enterocytes into capillaries
Large chain FAs - move via endocytosis into enterocytes and then become resynthesise into TGAs where they are incorprated into chylomicrons (lipoproteins) -> move into lymph via exocytosis
What transporters are involved in water balance in the small bowel and where are these found?
Na/glucose
Na/AA
Jejunum and ileum
When does removal of water take place in the small bowel?
Post-prandial (after food)
What vitamins are fat and water soluble?
Fat - ADEK
Water - BCH
How does transport of a fat soluble and water soluble vitamin differ?
Fat soluble - passively diffuse having been incorprated into micelles then incorparated into chylomicrons
Water soluble - moved via active transporters
What receptors do HAG work on?
Histamine - H2
ACh - M3
Gastrin - CCK2
How role does CCK play in bile secretion and what signals its release?
30mins after food eaten it will enter as chyme into duodenum -> release of CCK
CCK causes gallbladder to contract and release bile
It also causes relaxation of the Sphincter of Oddi (allows bile to enter D2)
How are bile salts created and where are they created?
In liver
Cholesterol broken down by hepatocytes into cholic acid (primary bile salt)
Travels to gallbladder for storage and concentration
What is bile made of?
95% water Cholesterol Bile salts Bilirubin Alkaline in nature
Why are bile salts amphiatic (hydrophobic on one end and hydrophillic on the other) nature important?
It allows the lipids to be formed into mixed micelles which allows TAG-lipase (from pancreas) to attack and further break down into monoglycerides and free FAs
What is perastalsis?
Relaxation of GI wall followed by contraction triggered by gut wall distension
What makes up the enteric nervous system?
ENS = brain of the gut
Submucosal plexus - submucosa
Myenteric plexus - muscularsis externa - in between circular and longitudinal layers of muscle
