Question

A) In the experiment, you have measured hormones Gastrin, Cholecystokinin (CCK), Gastric Inhibitory Polypeptide (GIP), Secretin, and Motilin over a 2 hour period following consumption of both meals. Describe any changes (i.e. increase, decrease or no change in hormone levels) following consumption of the two different meals (High Fat and High Protein).

B) For the hormone(s) that were identified as increasing in response to the meal, explain:

• The mechanism(s) behind their secretion (i.e. what is the stimuli for their secretion) (2.5 marks)
• What is their role when secreted? (2.5 marks)

Answer 1

part A. Gastrin, Cholecystokinin (CCK), Gastric Inhibitory Polypeptide (GIP), Secretin, and Motilin are all digestive hormones that aids in digestion.
Gastrin is secreted by the stomach in response to food. The food rich in proteins stimulates increased level of gastrin.
Cholecystokinin :  it is released from the small intestine. Its secretion increases in presence of carbohydrate rich foods (high fat).
Gastric inhibitory polypeptide : released by small intestine in response to food. It is secreted in equal amounts in response to high protein and high fat food.
Secritin :secritin is secreted by small intestine in response to acidic chyme entering it. It inhibits gastric acid secretion from stomach and release bicarbonate which helps maintain the ph levels and protect small intestine from the damage caused by gastric acid.
Motilin : motilin is secreted by small intestine in absence of food or during starvation.
So we can say that gastrin secretion increases in presence of high protein diet while cholecystokinin secretion icreases in response to high fat diet. Gastric inhibitory polypeptides are released in presence of faty as well as protein rich food in same amounts.
part B.  The hormones released in presence of food are :

- gastrin : stimulates release of gastric acid and intrinsic factor from parietal cells.
It also stimulates release of pepsinogen from chief cells. This helps in digestion of proteins.
- cholecystokinin: stimulates gallbladder contraction and relaxation of sphincter of oddi to release bile. Also stimulates release of pancreatic enzymes. This helps in digestion of carbohydrates, fats and lipids.
- gastrin inhibitory polypeptides : released during late phase of digestion and stimulates release of insulin from pancreas that helps in uptake of glucose by the cells.