Hormonal and Neuronal Control

Question 1

What are the basic functions of the GIT

Answer 1

Absorption, digestion, waste excretion, microbiome and barrier to pathogen entry

Question 2

What are the three motility movements in the GIT

Answer 2

Peristalsis, retropulsion and segmental mixing

Question 3

What is peristaltsis

Answer 3

Is progressive waves of contraction that move from one section of the GI tract to another. Will push the mass or bolus from one segment to the next

Question 4

What is segmental mixing

Answer 4

Short segments will contract (circular muscles) and they occur randomly across the gut. This alternative segmental contractions will churn the intestinal contractions, promoting mixing and increased interaction with the absorptive epithelium

Question 5

What is the Vago-Vagal reflex

Answer 5

the presence of food in the stomach will promote the afferent vagal nerves to be stimulated, Signals return to the CNS via the vagus. Efferent signals will then return to the stomach and promote fundas and body smooth muscle cell relaxation to accommodate food. Will also signal to the stomach cells to increase acid secretion

Question 6

What is the Cephalic Response

Answer 6

Occurs in the thought, sight or smell of food, leads to salivation, gastric acid and pepsin secrettion and relaxation of the stomach

Question 7

What hormones do the G cells produce

Answer 7

Gastrin

Question 8

What hormones do the D cells produce

Answer 8

Somatostatin

Question 9

What products do the ECL cells produce

Answer 9

Histamine

Question 10

What cells produce HCl

Answer 10

Parietal Cells

Question 11

What receptors do parietal cells have to promote Acid secretion

Answer 11

H2 receptors, Gastrin (CCK8) receptors and M3 for ACh

Question 12

What effects does somatostatin have

Answer 12

Will act on G cells and ECL cells to stop producing factors that promote Acid secretion. Can also have direct action n the parietal cells to stop producing acid

Question 13

Where are the D and G cells located

Answer 13

Antrum of stomach

Question 14

What stimulates D and G cells

Answer 14

G cells - amino acids

D cells - Increased H+ cells

Question 15

What mediates the release of CCK

Answer 15

Fatty acids and AA

Question 16

What cells release CCK

Answer 16

I cellss

Question 17

What are the effects of CCK

Answer 17

Promote the release of pancreatic enzymes and bile through the sphincter of Oddi, inhibits gastric emptying, increased acid secretion and also supresses apetite

Question 18

What can cause the release of secretin

Answer 18

Fatty acids and AA

Question 19

Function of secretin

Answer 19

The promotion of bicarbonate release from pancreas to neutralise the pH, over time this will then promote pyloric emptying

Question 20

What cells release Secretin

Answer 20

S cells

Question 21

What are the mechanisms of chemical sensing in the gut

Answer 21

Taste receptors on the gut wall (bitter and Umami) will cause Enterochromaffin and enteroendocrine cells to release serotonin into the submucosa to activate neurons in the ENS to control contraction and motility. Serotonin can also stimulate the vagus and is an important mechanism of nausea

Question 22

What are L cells and their function

Answer 22

They have Sweet receptors on them and they can release a variety of hormones that act on the CNS to regulate appetite and insulin secretion

Question 23

What movements are typically observed in retropulsion

Answer 23

Contrictions running towards pylorus that allows for the mixing of pancreatic juices and bile with food activating and facilitating digestion

Question 24

What is the mechanism of motility from the duodenum to the jejunum

Answer 24

Digestion breakdown products will regulate the movement of food down the GIT. Also distension/stretch receptors will promote movement

Question 25

What is the mechanism of motility from the Jejunum to the colon

Answer 25

Predominately Distension and strech, limited AA etc. Presence of SCFA will also modulate activity

Question 26

Mechanisms of Defecation

Answer 26

Build up of contents will promote the urge to deficate, mass movement contractions will promote the faecal matter from colon to rectum

Question 27

What is the migrational motor complex

Answer 27

In starvation is a wave of contractions (very sloww) that wull remove dead/dying bacteria as to restrict overgrowth. Promoted by Motilin