Hypothalamic control of Eating

Question 1

What are the the 2 basic preabsorptive satiety factors (short-term signals)?

Answer 1

1. gastric distension
2. nutrients in intestine

Question 2

What are the oropharyngeal satiefy factors?

Answer 2

related to taste and smell

if the animal is fasted - they will increase appetite

if the animal is fed - they will decrease appetite

Question 3

What is the signalling pathway for gastric distention?

Answer 3

1. food enters stomach, causing it to stretch
2. mechanoreceptors activated
3. signal sent via vagal afferents
4. synapse on the nucleus tracus solitarius in medulla
5. this decreases food intake

Question 4

What hormone is made in the duodenum in response to fatty meals?

Answer 4

colecystokinin (CCK)

Question 5

What are the 3 effects of CCK?

Answer 5

1. gallbladder contraction
2. pyloric constriction
3. increased gastric contractions

Question 6

What is the signalling pathway for CCK?

Answer 6

CCK secretion

CCk activates CCK receptors

increased signalling form vagal afferents

increased signalling in the NTS

decrease in food intake

Question 7

What hormone causes an INCREASE in appetite?

Answer 7

ghrelin

Question 8

Where is ghrelin made? When?

Answer 8

Made in the stomach during fasting

Question 9

What are the symptoms of Prader-Willi syndrome and how does this tie into our hunger discussion?

Answer 9

1. fetal hypotonia
2. mentlal retardation
3. hypogonadotropic hypogonadism
4. obesity
5. hyperphagia

they have excessive eating habits because they have excessive ghrelin secretion

Question 10

What is the controlled variable in long-term signals of satiety?

Answer 10

fat stores controlled by “adiposity” signals

Question 11

What hormone is released from adipocytes to decrease food intake?

Answer 11

leptin

Question 12

Where are the sites of action for leptin?

Answer 12

brain stem and hypothalamus

Question 13

What was the effect of NTS response to gastric stretch in the presence of leptin?

Answer 13

leptin made the NTS more responsive to stretch

Question 14

Lesions of the lateral hypothalamic area will result in what?

Answer 14

aphagia due to damage to the medial forebrain bundle

• you have reduced motivation to eat
• you can potentiallh have reduced motor function
• loss of neurons that synthesize Orexin, which is an orexigenic peptide that makes us eat more

Question 15

What happens with stimulation of the lateral hypothalamic area?

Answer 15

you get an increase in orexin in the brainstem, which makes you eat more/grow

Question 16

What affect do the paraventricular nucleus neurons have on food intake? How?

Answer 16

They decrease food intake by releasing “catabolic” neurotransmitters int he brain - corticoropin releasing hormone

Question 17

What are the two populations of neurons within the arcuiate nucelus?

Answer 17

neuropeptide Y neurons

melanocortin (POMC-derived) neurons

Question 18

Fill in the blank:

Neuropeptide Y neurons project to both the PVN and LHA to ____ food intake

Melanocortin neurons project ot he PVNa nd LHA to ____ food intake

Answer 18

increase

decrease

Question 19

Leptin ____ NPY neurons and _____ melanocortin neurons to _____ food intake

Answer 19

inhibits the NPY

activates the melanocortin

decreases food intake

Question 20

What affect does ghrelin have on the ARC?

Answer 20

it activates NPY neurons to increase eating

Question 21

How does the NST reduce food intake?

Answer 21

it inhibits various cranial nerve nuclei involved in eating

so trigeminal motor

vagus dorsal motor

hypoglossal

nucleu ambigus