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Neurobiology (3350) > Lecture 16 - Hypothalamus and feeding > Flashcards

Lecture 16 - Hypothalamus and feeding Flashcards

1
Q

What are the 3 components to keep homeostatis?

A
  • Humoral response – stimulate or inhibit secretion of hormones in the pituitary gland into the bloodstream
  • Viscero-motor response – adjust output of ANS sympathetic and parasympathetic systems
  • Somatic motor response – motivate appropriate somatic motor behaviour
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2
Q

Feeding behavior

A

an integrated activity of autonomous and voluntary nervous systems informed by the sensory nervous system of external environment states.

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3
Q

What happens to absorbed nutrients in the anabolism during the prandial state

A

Absorbed nutrients become

  • triglycerides (to adipose (fat) tissue)
  • ketones, fatty acids, glucose
  • Glycogen (to liver & skeletal muscles)
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4
Q

What are the types of responses in energy balance and feeding?

A

Short-term response

  • Regulate meal size and frequency - stop eating or eat more (when hungry)

Long-term response

  • Maintain body fat reserves
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5
Q

Lipostatic hypothesis

A

Brain monitors the amount of body fat and acts to “defend” the energy store against perturbations like starvation or forced eating.

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6
Q

What monitors quantity of body fat

A

CNS

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7
Q

Briefly explain the discovery of leptin by coleman and friedman

A

They did Blood exchange by adjoining circulatory systems (Parabiosis) to compare wildtype mice, obese mice and diabetic mice

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8
Q

Describe what Coleman and friedman found following the Parabiosis of ob/Wild-type (WT) mice

A
  • ob mouse quickly loses weight
  • Conclusion: Blood factor in WT mouse shared with ob mouse that signals satiety - « Leptin »
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9
Q

Describe what Coleman and friedman found following the Parabiosis of db/Wild-type (WT) mice

A
  • WT mouse dies two weeks after due to
    starvation
  • Conclusion: There is an elevated blood factor in db that induced starvation in WT mouse
  • db mouse is missing a receptor for this blood factor, and in response, this factor is overproduced in db mouse
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10
Q

Describe the key findings of Coleman and friedman’s parabiosis

A
  • ob/ob mice do not produce leptin but has receptors for leptin
  • db/db mice have no leptin receptors but produce leptin (leading to overproduction of leptin)
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11
Q

Why did WT mice die due to starvation after the parabiosis with db mice

A
  • The WT mice is healthy and following parabiosis got lots of leptin from db mice (since it was overproduced in db/db mice)
  • WT mice leptin levels rise up making it not eat leading to death
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12
Q

Leptin infusion causes what?

A

suppresses food intake and causes weight loss

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13
Q

Does leptin treatment work for people with leptin receptor mutations

A

No

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14
Q

Describe leptin

A
  • Acts on the brain to suppress food intake &
    increase energy expnediture (metabolism)
  • Circulates in the blood
  • Maintains homeostasis of fat tissue
  • A specific group of neurons detects leptin levels to maintain optimal levels of stored energy in fat tissue
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15
Q

Following a Lesion of Paraventricular nucleus, what happens to a mice? What does this finding suggest?

A
  • mice became fat
  • satiety center
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16
Q

Following a lesion of the lateral hypothalamic nucleus, what happens to a mice? What does this finding suggest?

A
  • mice became skinny
  • hunger centre
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17
Q

In the hypothalamus, there are 2 gates of neurons. What are their names? What is there relationship to MC4R

A
  • Proopiomelanocortin (POMC) - agonist of MC4R
  • Agouti-related peptide (AgRP) - antagonist MC4R
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18
Q

What is the role of Proopiomelanocortin (POMC)

A
  • POMC activates PVN and inhibits LH
  • shows satiety
  • increased levels of leptin activate POMC
19
Q

what is the role of Agouti-related peptide (AgRP)

A
  • NPY/AGRP activates LH and inhibits PVN
  • when hungry
20
Q

What are the first order neurons in the Hypothalamic melanocortin system? Where are they located?

A
  • Agouti-related peptide (AgRP/NPY)
  • Proopiomelanocortin (POMC)
  • In the arcuate nucleus
21
Q

What are the 2nd order neurons in the Hypothalamic melanocortin system

A
  • Paraventricular nucleus
  • Lateral Hypothalamic nucleus
22
Q

Describe Hypothalamic melanocortin system Neurons

A
  • in the arcuate nucleus
  • express leptin receptors
  • integrate peripheral signals to maintain energy homoeostasis.
23
Q

Leptin activates _____ neurons in the arcuate nucleus

A

aMSH/CART

24
Q

Describe aMSH

A

alpha-melanocyte stimulating hormone
produced by POMC neurons

25
Q

Describe CART

A

Cocaine and amphetamine regulated transcripts

26
Q

aMSH/CART neurons mediates which three responses

A
  1. Humoral response
  2. Viscero-motor response
  3. Somatic motor response
27
Q

What happens to the humoral response when there are elevated levels of leptin ?

A

Induction of humoral response

  • Increase in activity of ‘satiety’ neurons in the Paraventricular nucleus
  • Release of TSH and ACTH
  • Increase in metabolism and cortisol (stress) release
28
Q

What happens to the viscero-motor response when there are elevated levels of leptin ?

A

Induction of viscero-motor response

  • From axons that project from paraventricular
    and arcuate nuclei
  • Increase activity of ANS sympathetic
  • Decreased activity of ANS parasympathetic
29
Q

What happens to the somatic motor response when there are elevated levels of leptin ?

A

Induction of somatic motor response

  • Inhibition of ‘hunger’ neurons in lateral
    hypothalamic area
  • Decreased food intake
30
Q

What happens to the viscero-motor response when there are reduced levels of leptin ?

A
  • Inhibition of ANS sympathetic
  • Stimulation of ANS parasympathetic
31
Q

What happens to the humoral response when there are reduced levels of leptin ?

A
  • Inhibition of PVN
  • Inhibition of PVN stimulation of TSH and ACTH release
32
Q

What happens to the somatic response when there are reduced levels of leptin ?

A
  • Stimulation of feeding behaviour through
    stimulation of lateral hypothalamic area
33
Q

Reduced leptin leads to what in relation to NPY/AgRP neurons?

A
  • leads to activation of NPY/AgRP neurons
  • Increased levels of leptin suppresses AgRP
34
Q

True or False. Leptin inhibits NPY and AgRP expressing neurons in the arcuate nucleus

A

True

35
Q

Leptin levels decrease when…

A

There is Increased food intake. which leads to Reduction of
- body temperature
- energy expenditure
- reproductive function

36
Q

Leptin levels rise when…

A

The Food intake goes down. which leads to increased
- body temperature
- energy expenditure

37
Q

Where is orexin/hypocretin found?

A

hypothalamus

38
Q

What is the role of hypocretin ?

A

When it is time to be awake, there are certain neurons in your brain that release hypocretin. This hypocretin tells the brain to be awake.

39
Q

Describe Cholecystokinin

A

a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein.

40
Q

What is the cause of reduced meal frequency and size

A

When Both gastric distension (stretching of stomach) and CCK signals converge on axons in vagus nerve

41
Q

Describe the hunger cycle with Ghrelin

A
  1. Hunger stimulates the release of ghrelin from the stomach
  2. Ghrelin travels in the blood to the hypothalamus
  3. Stiumaltion of appetite
  • eating causes blood levels of ghrelin to decrease
42
Q

Describe the satiety cycle with GLP-1 (glucagon-like peptide-1)

A
  1. Eating stimulates release of GLP-1 from the intestine cells within 15 min
  2. GLP-1 travels in the blood to the brain stem to stimulate brain cells to release more GLP-1
  3. GLP-1 acts on hypothalamus
  4. Inhibits appetite

Eating causes blood levels of GLP1 to rise 2-4 folds and peaked at 60min

43
Q

Where is leptin produced

A
  • produced by adipose tissue, it suppresses appetite as levels increase

Neurobiology (3350) (8 decks)

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