Lecture 23: Motivation

Question 1

Lesions in the ventromedial hypothalamus cause

Answer 1

Obesity and over-eating

Increased bodyweight

Question 2

Lesions in the lateral hypothalamic area cause

Answer 2

Decreased weight gain

Loss of appetite

Question 3

Location of and projections of NPY/AgRP neurons

Answer 3

Located in the ventromedial part of the arcuate nucleus, itself located ventromedially in the hypothalamus.
These project to:
- Lateral hypothalamic area to stimulate feeding behaviour and
- Paraventricular nucleus of the hypothalamus to inhibit secretion of hormones controlling ACTH and TSH.

Question 4

Location and projections of the pro-opiomelanocortin (POMC) neurons

Answer 4

Found in the arcuate nucleus that is located in the ventromedial hypothalamus.
These project to:
- PVN to stimulate release of ACTH and thyrotropin from anterior pituitary to increase metabolism and activation of brain stem neurons as well as ANS for utilisation of brown fat for heat
- Lateral hypothalamic area to release αMSH which binds to MC4 receptor in lateral hypothalamic area and inhibits the activity of those cells, thereby decreasing appetite.

Question 5

Location and function of the MC4 receptor

Answer 5

Located in the lateral hypothalamic area and inhibits the activity of second order neurons to inhibit feeding behaviour

Question 6

Function of leptin

Answer 6

Leptin stimulates neurons containing the peptide α‐melanocytestimulating hormone (α‐MSH) which acts via specific receptors (MC3/4) in the lateral hypothalamus to decrease food intake.
Leptin also inhibits another population of neurons in the arcuate nucleus that contain the peptide neuropeptide Y (NPY) which also acts via specific receptors in the lateral hypothalamus to stimulate food intake.

Question 7

α-MSH acts through which type of receptors?

Answer 7

Melanocortin receptors, specifically MC3 and MC4 receptor in the case of appetite and metabolism