Regulation of Appetite

Question 1

Which nuclei are important for appetite regulation and where are they

Answer 1

paraventricular nucleus
Arctuate nuclei
Found in the hypothalamus

Question 2

Where is the arctuate nucleus found and what is its function

Answer 2

Base of the brain at the hypothalamus (3rd ventricle runs through it)
Incomplete blood barrier for direct activation by peripheral signs (nutrients, hormones, concentration, temp.)

Question 3

What are the 2 neuronal populations of the arctuate nucleus and what are their roles

Answer 3

Neuropeptide Y/Agouti-related peptide (NPY/Agrp) - stimulate food intake (medial)
Proopiomelanocortin (POMC) - inhibit food take (lateral)

Question 4

How does Agouti-related peptide carry out its function

Answer 4

1. Release of neuropeptides (Agrp)
2. Agrp competitively blocks the satiating signal from a-MSH on the paraventricular nucleus
3. increase in food intake

Question 5

Which mutations have been linked with morbid obesity

Answer 5

POMC deficiency
MC4R mutation
Can also cause ginger hair due to reduction in MSH

Question 6

What is leptin

Answer 6

Hormone secreted by white adipose tissue
Binds to receptors in the hypothalamic circuits
Stimulates anorexigenic behaviour
high body fat = high leptin

Question 7

What is Ghrelin

Answer 7

peptide hormone that regulates short-term appetite control by promoting eating behaviours
Secreted from the stomach in increasing quantities
Once one has eaten ghrelin decreases

Question 8

What is Peptide YY3-36

Answer 8

peptide hormone that regulates short-term appetite control by suppressing eating behaviour
Secreted from the ileum and colon in response to a meal
originally 38 but last 2 amino acids are cleaved

Question 9

When does an individual perceive thirst

Answer 9

Body fluid osmolality increases
Blood volume reduced
Blood pressure reduced

Question 10

What is vasopressin

Answer 10

Acts on the kidneys to regulate urine osmolality
Plasma vasopressin low = large volume dilute urine
Plasma vasopressin high = small volume conc. urine

Question 11

Describe vasopressin release

Answer 11

osmoreceptors
Organum vasculosum and Subfornical organ and Hypothalamus
Cells shrink or cell to send signals to vasopressin releasing cells in the hypothalamus

Question 12

Describe the immediate relief of thirst

Answer 12

Thirst is decreased by drinking before sufficient water has been absorbedly the GI tract
Receptors in the mouth, pharynx, oesophagus
Short-lived relief

Question 13

How does angiotensin II relate to thirst

Answer 13

Evokes thirst sensation
SFO neurones activated
Regulates homeostasis

Question 14

Draw a diagram of the hypothalamus

Answer 14

Refer to slides

Question 15

How does POMC carry out its function

Answer 15

1. Release of neuropeptides (alpha-MSH)
2. a-MSH bind to melanocortin 4 receptor (MC4R) on the paraventricular nucleus
3. Activation of MC4R causes decrease in food intake

Question 16

Which other brain areas give signals

Answer 16

Higher centres
Amygdala - emotion memory
Lateral hypothalamus
Vagus nerve via the brainstem

Question 17

How is leptin related to obesity

Answer 17

Obese humans usually have high leptin
Obesity is due to leptin resistance
Leptin is ineffective as a leptin drug

Very small no. of cases of people who do not have leptin

Question 18

What are the actions of PYY35

Answer 18

Directly modulates neurones in the arctuate nucleus
inhibits NPY release
Stimulates POMC neurones
Decreases appetite

Question 19

What are the actions of ghrelin

Answer 19

Directly modulates neurons in the arctuate nucleus
Stimulates NPY/Agrp neurones
Inhibits POMC neurones
Increases appetite