Physiology

Question 1

What 3 secretagogues induce HCl production?

How do they increase the HCl production?

What cell do they activate?

Answer 1

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

Question 2

Specifically where in the stomach is HCl produced and what enzyme is involved?

Answer 2

In gastric pit lumen outside parietal cells

H+/K+/ATPase pump

Question 3

Name the 3 phases of gastrin secretion

Answer 3

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

Question 4

During the cephalic phase of gastric secretion what causes an increase in HCl production?

Answer 4

Vagus nerve stimulates production of HAG
Histamine
ACh
Gastrin

Question 5

Describe what happens to food when it enters the stomach in terms of movement through the stomach?

Answer 5

Tonic waves push food towards antrum

Slow antral waves move food towards pyloric sphincter where when it is too large - RETROPULSION

Question 6

What part of brain controls appetite? What nerves stimulates appetite and what does it act on? Same for inhibits appetite?

Answer 6

Hypothalamus
Stimulates - orexigenic neurons - lateral hypothalamic
Inhibits - anorexiogenic neurons -ventromedial nuclei

Question 7

What part of brain controls vomiting?

Answer 7

Medulla

Question 8

What three secretagoues also have an impact on hunger. What cells produce them and where are these cells found?

Answer 8

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 -

Question 9

How does small intestine deal with highly acidic chyme?

Answer 9

Duodenum contains Brunner’s Glands which release an alkaline substance to neutralise

Question 10

What is a TGA?

Answer 10

Triglcyeride - consumed from fat

Three glycerides = 3x glycerol + FA chains

Question 11

What enzyme hydrolyses emulsions into free fatty acids? What releases it and what induces the organ to release it?

Answer 11

TGA-lipase

Released by panceras which is initated by release of CCK from I cells (duodenum and jejunum)

Question 12

What is emulsion?

Answer 12

Combination of fat droplets and bile salts (produced by liver)

Question 13

When a micelle reaches an enterocyte then what happens? How do lipids reach blood stream?

Answer 13

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

Question 14

What transporters are involved in water balance in the small bowel and where are these found?

Answer 14

Na/glucose
Na/AA
Jejunum and ileum

Question 15

When does removal of water take place in the small bowel?

Answer 15

Post-prandial (after food)

Question 16

What vitamins are fat and water soluble?

Answer 16

Fat - ADEK

Water - BCH

Question 17

How does transport of a fat soluble and water soluble vitamin differ?

Answer 17

Fat soluble - passively diffuse having been incorprated into micelles then incorparated into chylomicrons
Water soluble - moved via active transporters

Question 18

What receptors do HAG work on?

Answer 18

Histamine - H2
ACh - M3
Gastrin - CCK2

Question 19

How role does CCK play in bile secretion and what signals its release?

Answer 19

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)

Question 20

How are bile salts created and where are they created?

Answer 20

In liver
Cholesterol broken down by hepatocytes into cholic acid (primary bile salt)
Travels to gallbladder for storage and concentration

Question 21

What is bile made of?

Answer 21

95% water
Cholesterol 
Bile salts
Bilirubin 
Alkaline in nature

Question 22

Why are bile salts amphiatic (hydrophobic on one end and hydrophillic on the other) nature important?

Answer 22

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

Question 23

What is perastalsis?

Answer 23

Relaxation of GI wall followed by contraction triggered by gut wall distension

Question 24

What makes up the enteric nervous system?

Answer 24

ENS = brain of the gut
Submucosal plexus - submucosa
Myenteric plexus - muscularsis externa - in between circular and longitudinal layers of muscle

Question 25

Describe the muscle wall during peristalsis?

Answer 25

Behind bolus of food - circular contract, longitudinal relax

Infront - circular relax, longitudinal contract

Question 26

What cell is responsible for the slow wave contraction of gut wall and hence rate of perstalisis?

Answer 26

Intersital cells of Cajal AKA pacemaker cells

Question 27

How does the ENS induce peristalsis

Answer 27

Causes depolarisation by opening Ca2+ channels

Question 28

What chemicals cause relaxation and contraction of gut wall?

Answer 28

ACh - contraction

NO - relaxation (same as in blood vessels)

Question 29

What do acinar cells produce?

Answer 29

Proteases

Question 30

What do the following brush border enzymes act on and produce?

Maltase
Lactase
Sucrase

Answer 30

Maltase - disaccharide = glucose and glucose
Lactase - disaccharide = glucose and galactose
Sucrase - sucrose = glucose and fructose

Question 31

The loss of which enzyme is one of the key features in the development of steatorrhoea?

Answer 31

Lipase

Question 32

What is the normal intragastric pH?

Answer 32

2

Question 33

Pernicious anaemia is associated with other autoimmune conditions. True or false?

Answer 33

True

Question 34

What do chief cells produce?

What does it become when hits gastric acid?

Answer 34

Pepsinogen -> pepsin

Question 35

What cells produce HCl?

Answer 35

Parietal cells

Question 36

What cells produce somatostatin?

Answer 36

D cells

Question 37

What does enterochromaffin-like cells produce?

Answer 37

Histamine