control of appetite

Question 1

3 long term afferent signals that affect appetite/energy expenditure

Answer 1

1. leptin
2. fat
3. insulin

Question 2

2 meal related afferent signals that affect appetite/energy expenditure

Answer 2

1. ghrelin
2. PYY/ GLP-1/ CCK

Question 3

3 factors affecting energy output of body (i.e. calorie burning)

Answer 3

1. basal metabolic rate (2000 cal)
2. activity (500cal)
3. diet induced thermogenesis (10% of diet)

Question 4

what is the role of leptin

Answer 4

a hormone that helps to maintain long-term normal body weight -> it is essential for determining the feeling of hunger

Question 5

which organ controls the appetite regulation

Answer 5

the hypothalamus

Question 6

what are the 2 independent appetite control centres

Answer 6

1. the satiety centre
2. the hunger centre

Question 7

the satiety centre - where, how does it work and what do lesions in this area cause

Answer 7

1. located in the ventromedial nucleus of the hypothalamus
2. electrical stimulation elicits sensations of “fullness” and inhibit feeding responses (anorexigenic) even in the presence of food
3. lesions here have been shown to be involved in continuous food intake without nutiritional need

Question 8

what is hyperphasia

Answer 8

continuous food intake

Question 9

the hunger centre - where, how does it work and what do lesions in this area cause

Answer 9

1. located in the lateral hypothalamic area
2. stimulation results n feeding responses (orexigenic) even after adequate food intake
3. lesions result in long lasting cessastion of food intake

Question 10

what is aphagia

Answer 10

cessation of food intake

Question 11

what is the arcuate nucleus and what is its role in appetite

Answer 11

a structre in the mediobasal hypothalamus that acts as the processing centre for the two other appetite control centres and works to integrate signals for various appetite afferent inputs

Question 12

what is the role of ghrelin in appetite control and how does it achieve this

Answer 12

1. key player in driving the sensation of hunger
2. it is released from the stomach during fasting as a direct response of mechanoreceptor firing from reduced strech -> acts on the arcuate nucleus to inhibit and stimulate satiety/hunger neurons
3. ghrelin levels fall within approximately an hour of food intake

Question 13

how is the vagus nerve involved in appetite control

Answer 13

stomach mechanoreceptors also relay info to the vagus nerve which then relays this to the nucleus tractus solitarii -> triggers inhibition and stimulation of corresponding centres in the arcuate nucleus

Question 14

describe the role of mechanoreceptors, chemoreceptors, CKK, PYY, GLP1, insulin in satiety (5)

Answer 14

1. info is sent via the vagus nerve from the mechanoreceptors of the stomach to the nucleus tractus solitarii -> triggers inhibition/stimulation of certain arcuate nucleus centres
2. chemoreceptors in the small intestine respond to the presence of glucose, amino acids etc.
3. CCKs are released from I-cells of the small intestine in response to nutrients -> influence satiety by action on CCK receptors located in peripheral vagal afferent terminals
4. peptide YY & GLP1 are co-secreted postprandially from L-cells in the distal intestine -> anorexigenic effects in the arucate nucleus
5. insulin secretion is response to increased glucose levels acts on the arcuate nucleus in a similar manner to the peptide hormones

Question 15

how is leptin involved in long term appetite control

Answer 15

1. leptin is secrete by fat cells -> levels increase proportionally to adipose tissue
2. leptin receptors are expressed in the appetite control areas of the brain -> drives anorexigenic regions
3. increased lipid concentration results in leptin release -> satiety

Question 16

role of leptin in obesity

Answer 16

leptin resistance is often seen leading to reduced satiety, over-consumption of nutrients, and increased total body mass