Control of the GI System

Question 1

What is responsible for the control of the GI system?

Answer 1

The enteric nervous system, which can function independent of the central nervous system.

Question 2

What reflex does the enteric nervous system initiate in response to food?

Answer 2

The gastrocolic reflex, which stimulates the colon to push food matter further down the tract to the rectum to make room for the new food.

Question 3

What hormone do mucosal cells initially release in response to food entering the stomach? What does it stimulate?

Answer 3

Gastrin. This promotes the release of HCl from pareital cells and pepsinogen from the chief cells. It also increases stomach motility for the formation of chyme.

Question 4

What condition causes the inhibition of gastrin release in the stomach?

Answer 4

A stomach pH < 3

Question 5

What two hormones are released in response to chyme reaching the duodenum? What specifically promotes their release?

Answer 5

1) Secretin: released in response to low pH
2) CCK: released in response to the presence of fats

Question 6

Where does secretin act? What does it cause?

Answer 6

1) The pancreas -> the release of bicarbonate.

This functions to help neutralize the chyme’s HCl

2) The stomach: decreses motility and HCl release.

Question 7

What are the destinations for CCK? Why?

Answer 7

1) The pancreas, to release pancreatic enzymes (lipase)

2) gallbladder, to release bile (bile salts).

The combination of these two reactions helps in the digestion of fats.

It also acts to decrease stomach motility.