Control Of Body Energy Supplies

Front 1

What is the big problem with body weight and your brain?

Back 1

Your brain isn't concerned with how much you weigh, it is concerned with the energy stores you have available.
From older times where food was scarce instead of plentiful

Front 2

What part of the brain controls body energy supplies? What regions does this part of the brain have that influence body energy supplies?

Back 2

The hypothalamus
Regions devoted to satiety and hunger

Front 3

The hypothalamus has outflows via what pathways?

Back 3

Behavioral (cortical)
Autonomic
Hormonal

Front 4

What are the arcuate nuclei?

Back 4

The relay for hormonal signals from the periphery

Front 5

Why are hormones from the periphery normally excluded?

Back 5

Because of the blood brain barrier

*Third ventricle has a leak blood brain barrier allowing the arcuate nuclei to have receptors for hormones from the periphery

Front 6

Which nuclei are associated with the behavior associated with hunger? Stimulation of this area causes what?

Back 6

The lateral hypothalamic nuclei
Stimulation causes hunger
Destruction causes loss of hunger

Front 7

Which nuclei are associated with behavior associated with satiety? Stimulation of this area causes?

Back 7

Ventromedial hypothalamic nuclei
Stimulation produces satiety and stops eating
Destruction produces loss of satiety and causes eating behavior

Front 8

Which nuclei are associated with the control of metabolism? Stimulation causes?

Back 8

Dorsomedial hypothalamic nuclei
Stimulation increases metabolic rate
Destruction decreases metabolic rate

Front 9

T or F: Axons from the arcuate nuclei go to the lateral hypothalamic, dorsomedial hypothalamic, and ventromedial hypothalmic nuclei.

Back 9

True

The arcuate nuclei has axons to all of the other nuclei

Front 10

T or F: The lateral and medial nuclei send axons to one another.

Back 10

True

Front 11

What type of feedback is found between the lateral and medial nuclei?

Back 11

Largely negative feedback, activate one to inhibit the other

Front 12

What is an orexigenic chemical?

Back 12

One that increases the sensation of hunger and produces eating behavior

Front 13

What are the three main orexigenic substances?

Back 13

Neuropeptide Y
Agouti-Related Peptide (AGRP)
Ghrelin

Front 14

What produces neuropeptide Y?

Back 14

Neurons in the arcuate nuclei

Front 15

What does neuropeptide Y act on?

Back 15

The axons of the neurons producing neuropeptide Y go to the lateral hypothalamic nuclei and activate lateral nuclei causing hunger

Front 16

T or F: AGRP is produced by the same neurons that produce neuropeptide Y.

Back 16

True

Front 17

What is the mechanism of AGRP?

Back 17

Axons from neurons in the arcuate nuclei go to lateral hypothalamic nuclei
They release NPY and AGRP as CO-neurotransmitters to activate the lateral nuclei
*Also inhibits the action of MSH (melanocortin) which inhibits satiety at the medial nuclei

Front 18

What is ghrelin and where is it produced?

Back 18

Hormone
Produced by the stomach during fasting

Front 19

What does ghrelin do?

Back 19

Binds to growth hormone secretagogue receptors on neurons in the arcuate nuclei
*Neurons with the ghrelin receptors are the ones that produce AGRP and NPY and causes them to be released causing hunger

Front 20

What is anorexigenic chemical?

Back 20

One that decreases the sensation of hunger and inhibits eating behavior

Front 21

What are the five main anorxigenic chemicals?

Back 21

CCK
Serotonin
Leptin
Cocaine and Amphetamine Related Transcript (CART)
Melanocortin (melanocyte stimulating hormone or MSH)

Front 22

Where does CCK come from and what causes its release?

Back 22

I cells of the intestine
Released due to presence of fats in the duodenum
Produces satiety

Front 23

T or F: CCK can not directly activate neurons of the ventromedial nucleus of the hypothalamus.

Back 23

False

It CAN directly activate neurons

Front 24

Where is leptin made and what do its levels correlate well with?

Back 24

Leptin is made by adipocytes
Levels correlate well with amount of adipose tissue

Front 25

What is leptin unable to do? How does it overcome this obstacle?

Back 25

Cross the blood brain barrier by itself
In a region near the arcuate nuclei, cells of the BBB express a transporter protein to move leptin into the CSF

Front 26

What is the mechanism of action of leptin?

Back 26

Binds to subset of neurons in the arcuate nuclei and activates them. These neurons send axons to ventromedial hypothalamic nuclei. When activated by leptin these axons release CART and MSH causing satiety

Front 27

MSH is working via which receptor?

Back 27

MC-4R receptor

Front 28

What is serotonin and what does it promote?

Back 28

Neurotransmitter in the brain localized to axons terminating in the ventromedial nuclei of the hypothalamus
Promotes satiety

Front 29

What three "events" does the brain monitor in order to balance control energy intake?

Back 29

1. How much food do I eat when I sit down to eat? - short term control
2. How long do I go between meals? - intermediate control
3. What are my current energy stores? - long term control

Front 30

What are the major players in determining how much food you eat per sitting?

Back 30

Mechanoreceptors in the stomach and small intestine
Hormone CCK

*Activates ventromedial hypothalamic nuclei and inhibits lateral hypothalamic nuclei, causing satiety

Front 31

What are the major players in determining how long you go between meals?

Back 31

Hepatic and intestinal chemoreceptors
Hypothalamic chemoreceptors (glucostats)

Front 32

Where do the vast majority of absorbed nutrients end up initially?

Back 32

Enter the portal vein and end up in the second capillary bed of the hepatic portal system

Front 33

Hepatic chemoreceptors are located where and what are they sensitive to?

Back 33

Located in the portal vein or as neurons innervating near hepatocytes
Sensitive glucose, amino acids, lipids

Front 34

How do the hepatic chemoreceptors work?

Back 34

The afferents from the chemoreceptors travel to the brainstem and synapse to secondary axons that travel to the hypothalamus and activate the medial hypothalamic nuclei and inhibit the lateral regions

Front 35

Where are hypothalamic glucostats found?

Back 35

Arcuate nuclei in the hypothalamus

Front 36

Describe hypothalamic glucostats and their role in producing satiety.

Back 36

Use glucose metabolites for energy
They express glucokinase, an important step in ATP prodution
High ATP causes potassium channel to shut down
Potassium accumulates in the neuron and depolarizes it
The axons of these neurons release serotonin in the medial hyopthalamic nuclei and produce satiety

Front 37

Ghrelin is released in _____________ quantities the longer you go between meals.

Back 37

Increasing

Front 38

What are the major players in knowing what your current energy stores are?

Back 38

Hormonal signals from the body
Leptin is best described
Hypothalamic glucostats are also included

Front 39

Leptin produced by adipose tissue is important to what?

Back 39

The adequacy of our energy store

Front 40

Why does the brain not get the message that we have too much adipose from leptin?

Back 40

High levels of leptin cause the transport protein to be downregulated, so the same amount of leptin crosses the BBB into the CSF