Gi - Hunger And Satiety

Front 1

3 main functions of digestive system

Back 1

Digestion
Absorption
Defecation

Front 2

What initiates feeding behavior?

Back 2

"Feeling" hungry --> neurons in cerebral cortex are firing. There are also memory and emotional aspects involved, which means the Limbic system is involved. Contributors:
-Time
-Smell or taste
-Color / Appearance

Front 3

What causes limbic cortical neurons to fire action potentials, triggering a feeling of hunger?

Back 3

Excitatory synaptic input from the HYPOTHALAMUS

Front 4

What are the 2 key nuclei in the hypothalamus with roles in hunger?

Back 4

1) Feeding center
2) Satiety center

Front 5

Feeding center

Back 5

When these neurons fire, they excite cortical neurons and produce feelings of hunger. The neurons are located in the lateral hypothalamus and contain GLUCOSENSITIVE neurons (fire when blood glucose gets low).

Front 6

Satiety center

Back 6

When these neurons fire, they inhibit the feeding center, leading to a lack of hunger (feeding center stops stimulating the cortex).
Located in the ventromedial hypothalamus and contain GLUCORECEPTOR neurons (fire when blood glucose levels are normal or elevated).

Front 7

What are the other two groups of neurons located in the arcuate nucleus of the hypothalamus that impact the feeding center?

Back 7

1) AGRP neurons
2) POMC neurons

Front 8

AGRP neurons

Back 8

-Agouti-related peptide
-neurotransmitter
-stimulates feeding center
-potent and long-lasting appetite stimulant
-stimulates hunger
-decreases metabolism
-inhibit POMC neurons

Front 9

POMC neurons

Back 9

-Proopiomelanocortin
-polypeptide neurotransmitter
-inhibits feeding center
-generate feeling of satiety
-inhibit AGRP neurons

Front 10

What directly stimulates the feeding center?

Back 10

1) AGRP neurons
2) Low blood glucose

Front 11

What directly inhibits the feeding center?

Back 11

1) POMC neurons
2) Satiety center
3) Blood glucose (normal/elevated)
4) Insulin
5) Mouth touch receptors
6) Peptide YY

Front 12

What inputs directly affect the satiety center?

Back 12

Vagal afferents --> stimulated by distension of the stomach.
This is the biggest reason why we STOP eating once we have begun.

Front 13

What can result from ablation of the satiety center?

Back 13

Hyperphagia

Front 14

What directly stimulates the POMC neurons to fire?

Back 14

1) Insulin
2) CCK
3) Cocaine

Front 15

What directly inhibits the POMC neurons?

Back 15

1) AGRP neurons

Front 16

What directly stimulates the AGRP neurons to fire?

Back 16

1) Ghrelin (polypeptide hormone released by oxyntic cells of the stomach). An empty stomach begins secreting ghrelin and produces a feeling of hunger.
(Lack of sleep tends to increase ghrelin secretion, while gastric bypass and ghrelin antagonist developed as an anti-obesity serum decreases it)

Front 17

What directly inhibits the AGRP neurons?

Back 17

1) Insulin (normal / elevated)
2) Leptin (released by adipocytes; acts to stimulate sympathetic discharge to increase basal metabolic rate. Leptin levels may be lowered in obesity, producing an increase in hunger and decrease in BMR)

Front 18

Contraction of the stomach and/or irritation of the mucosa of the stomach can have what effect?

Back 18

Stimulation of neurons to carry action potentials to the CNS, which are interpreted by the cortex as hunger and initiates feeding behavior.