Gi Physiology Lecture 1 Wittingham

Front 1

This part of the brain is associated with emotions.

Back 1

Limbic Cortex.

Front 2

What specific part of the brain initiates our hunger?

Back 2

Hypothalamus (a limbic structure)

Front 3

What are the two nuclei of the hypothalamus playing roles in hunger?

Back 3

1. Feeding center
2. Satiety center

Front 4

Where are the neurons of the feeding center located specifically?

What specific type of neurons are they?

Back 4

They are located in the lateral hypothalamus.

They contain glucosensitive neurons (they fire if blood glucose gets low).

Front 5

What do the neurons of the satiety center do?

Back 5

They inhibit the feeding center, leading to a lack of hunger.

Front 6

Where are the neurons of the satiety center located specifically?

What specific type of neurons are they?

Back 6

They are in the ventromedial hypothalamus.

They contain glucoreceptor neurons (fire when blood glucose levels are normal or elevated.

Front 7

Besides the Feeding center and Satiety center, what two other groups of neurons play a role in hunger?

Where are they located?

Back 7

1. AGRP Neurons
2. POMC Neurons

They are located in the arcuate nucleus of the hypothalamus.

Front 8

1. What does AGRP stand for?
2. What do these neurons do?

Back 8

1. Agouti-related peptide--a neurotransmitter

2. Stimulate the Feeding Center and inhibit POMC neurons.

Front 9

1. What does POMC stand for?
2. What do these neurons do?

Back 9

1. Proopiomelanocortin--a polypeptide neurotransmitter

2. Inhibit the Feeding Center and inhibit AGRP neurons.

Front 10

What inputs directly affect the Feeding Center? (Stimulators & Inhibitors)

Back 10

Stimulators:
1. AGRP Neurons

Inhibitors:
1. POMC Neurons
2. Satiety Center
3. Blood Glucose
4. Insulin
5. Mouth touch receptors
6. Peptide YY (from the colon)

Front 11

What inputs directly affect the Satiety Center?

Back 11

Most importantly Vagal afferents --these are stimulated by distension of the stomach.

This inhibits the cortical neurons that cause us to feel hungry.

Front 12

What stimulates and inhibits the POMC neurons of the arcuate nucleus?

Back 12

Stimulated by:
1. Insulin (released by pancreas during 'Good Times')
2. Cholecystokinin (released by duodenum to help digest fats)
3. Cocaine

Inhibited by:
1. AGRP Neurons

Front 13

What stimulates and inhibits the firing of AGRP Neurons?

Back 13

Stimulatd by:
1. Ghrelin

Inhibited by:
1. Insulin
2. Leptin

Front 14

What is ghrelin?

Back 14

A polypeptide hormone released by oxyntic cells of the stomach. It is octanoylated in its active form (addition of an 8 carbon fatty acid chain).

An empty stomach secretes Ghrelin and helps to produce feeling of hunger.

Lack of sleep can increase ghrelin production.

Front 15

What is Leptin?

Back 15

A polypeptide hormone released by adipocytes. It increases basal metabolic rates.

It may lowered in the obese.

Front 16

How can the flu affect the sensation of hunger?

Back 16

The irritation of the stomach's mucosa stimulates afferent neurons--this can be interpreted as hunger.

Front 17

Why might people have different food preferences?

Back 17

We link food to emotion, might be different for everyone.

Front 18

How does Gastric bypass help the obese?

Back 18

It reduces stomach volume and decreases ghrelin levels--thereby decreasing hunger.

Front 19

What is Obestatin?

Back 19

It is a polypeptide hormone that is encoded in the same gene as Ghrelin. However, it decreases the feeling of hunger.

Front 20

What does the obesity vaccine do?

Back 20

Induces antibodies against Ghrelin...thereby decreasing hunger.

Front 21

What psychological factors may be associated with our sensation of hunger?

Back 21

1. Time--we are used to eating at certain times of the day.
2. Smell and Taste--This is a learned preference (involving the hippocampus for memory formation).
3. Color/Appearance--Blue seems to suppress hunger

Front 22

What is Cholecystokinin (CCK)?

Back 22

A polypeptide hormone. It is released by I cells of the duodenum and upper jejunum due to the presence of food (fats & some proteins) in the small intestine.

Its presence stimulates POMC neurons which, in turn, inhibit the Feeding Center.

Front 23

What is Insulin?

Back 23

A pancreatic polypeptide released by beta cells of the Islets of Langerhans.

It stimulates the POMC neurons and inhibits the AGRP neurons in the arcuate nucleus (inhibits the Feeding Center and stimulates the Satiety Center).

Front 24

What provide long-term inhibition of the Feeding Center?

Back 24

1. Peptide YY
2. Glucoreceptor neurons in the Satiety Center (which decrease the firing of the Glucosensitive neurons in the Feeding Center).
3. Leptin

Front 25

What is Peptide YY?

When do its levels peak in the body?

Back 25

It is a polypeptide hormone that is secreted by the entire digestive tract, especially the ileum and colon.

PYY levels peak about 1-2 hrs. after a meal b/c the ileum and colon are so late in the digestive process. PYY levels are especially increased after a fatty meal.

A key long-term inhibitor of the Feeding Center.

Front 26

What is Leptin?

Back 26

A polypeptide hormone that is released by adipocytes in response to triglyceride synthesis in those cells. It signals the rest of the body that times are good and there are enough nutrients to be storing fat.

Front 27

What are 4 actions of Leptin?

Back 27

1. Inhibition of AGRP neurons (which stimulate hunger when active)

2. Activation of POMC neurons (which inhibit hunger)

3. Increase sympathetic nervous system activity (mobilizing food stores and increasing basal metabolic rate)

4. Decrease insulin release (inhibiting further storage of food stores)