Appetite

Question 1

What 3 stimuli in the body call for thirst regulation?
Which is most potent?

Answer 1

Blood fluid osmolality - most potent
Reduced blood pressure
Blood volume is reduced

Question 2

What is the control centre for appetite control and what does each area do?
How is one of them adapted for its function?

Answer 2

Hypothalamus
Arcuate nucleus control food intake. Does not have BBB
Has both inhibitory and stimulatory neurons (NPY/AGRP and POMC)

Paraventricular nucleus is affected by AGRP and POMC to produce other peptides

Ventromedial thalamus tells us we’re full

Lateral hypothalamus produces appetite stimulant peptides

Question 3

What are the appetite peptides hormones and where do they come from?

Answer 3

Leptin- lean hormone. Made by adipose tissue (high when high body fat, low when low body fat)
Ghrelin- enteroendocrine cells in stomach and SB
Peptide YY- terminal ileum

Question 4

What is the mechanism of action of leptin?
What tissue produces it?
How can this be affected in obese individuals?

Answer 4

Adipose tissue produces it
Inhibits NPY/AGRP and stimulates POMC receptors on hypothalamus
Sometimes sensitivity can be reduced resulting in resistance in people with high levels of leptin due to the constant high amounts

Question 5

How do GUT hormones affect our appetite?
What do they each inhibit/stimulate?

Answer 5

Ghrelin- stimulates appetite and increase gastric motility to help digest food. Stimulates NPY/AGRP and inhibits POMC
Peptide YY- inhibits food intake
Stimulates POMC and inhibits NPY/AGRP

Question 6

What is the hormone in control of haemostasis of blood osmolality?
Where is it stored?

Answer 6

ADH
Posterior pituitary

Question 7

Where are osmoreceptors found specifically?
Describe the mechanism of ADH secretion in response to osmoreceptor change

Answer 7

Subfornical region of hypothalamus
Cells shrink in size when blood plasma is more concentrated, exposing more cations channels on their surface. This stimulates a production in ADH and therefore fluid retention

Question 8

Describe the Renin-angiotensin mechanism
What 4 actions does angiotensin II have?

Answer 8

Low blood pressure is detected by juxtaglomerular cells, these release renin which converts angiotensinogen into angiotensin I. ACE turns this into angiotensin II
AII: Increases thirst, ADH production, vasoconstriction (sympathetically), aldosterone

Question 9

What receptor in the paraventricular nucleus is responsible for responding to neural peptides POMC, NPY and AGRP

Answer 9

MC4R