Appetite Regulation

Question 1

What are the 3 parts of the hypothalamus which regulate food intake and what do they do?

Answer 1

Ventromedial nuclei: satiety centre causing sensation of fullness
Lateral hypothalamic area: feeding centre causing sensation of hunger
Acruate nucleus: receives signals from GI tract and regulates satiety and hunger centres

Question 2

What is the role of mechanoreceptors in the stomach during hunger

Answer 2

• Mechanoreceptors in the stomach detect emptiness in the stomach and send slow signals through the vagus nerve in the medulla called the solitary nucleus
• The solitary nucleus sends fibres to the acruate nucleus in the hypothalamus
• The acruate nucleus sends fibres activating the feeding centre and fibres to inactivate the satiety centre

Question 3

What is the role of ghrelin in hunger

Answer 3

• Low blood glucose and slow firing of mechanoreceptors trigger g cells in the lining of stomach to release ghrelin into the blood
• Ghrelin travels to acruate nucleus causing stimulation of feeding centre and inhibition of satiety centre

Question 4

Role of mechanoreceptors in the stomach after eating

Answer 4

• Increased firing of mechanoreceptors detecting stretch in stomach travels through vagus nerve to acruate centre in hypothalamus
• Decreases feeding centre signals
• Increases satiety centre signals

Question 5

What is food broken down into as it passes through the small intestine?

Answer 5

Glucose, fats and amino acids

Question 6

What type of receptor detects nutrients in the stomach and small intestines?

Answer 6

Chemoreceptors

Question 7

What is the role of chemoreceptors in the stomach and small intestine?

Answer 7

It sends signals to enteric nervous system of the gastrointestinal tract which stimulates enteroendocrine cells to secrete various hormones

Question 8

Fats and proteins cause cells in the duodenum and jejenum to release what?

Answer 8

Cholecystokinin CCK

Question 9

Proteins cause L cells in the ileum and colon to release what?

Answer 9

Peptide YY

Question 10

Glucose causes L cells to release ..?

Answer 10

Glucagon like peptide 1 (GLP-1)

Question 11

What is the effect of Peptide YY on ghrelin?

Answer 11

Inhibits ghrelin secretion

Question 12

What does cholecystokinin do?

Answer 12

Triggers contraction of the gallbladder and gut motility

Question 13

What is the effect of GLP-1 on insulin secretion?

Answer 13

Increases secretion of insulin from pancreas

Question 14

What is the long-term satiety hormone, what does it do and where is it produced?

Answer 14

Leptin

• Acts on the hypothalamus directly to reduce hunger and increase satiety
• Produced by adipose cells so more adipose cells more leptin (try and reduce obesity)