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motivation Flashcards

1
Q

what is motivation?

A

driving force
physical need
wanting (hedonic aspect)

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2
Q

the hypothalamus maintains homeostasis by regulating 3 functions - what are they?

A
  • endocrine system
  • ANS
  • emotions and drive
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3
Q

what is catabolism?

A

when you’re hungry, glycogen is broken down to glucose, adipose tissue broken down to FA and ketones
-provides cells with energy

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4
Q

what is the opposite of catabolism?

A

anabolism

-glucose being stored

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5
Q

what is there long term regulation of?

A

body weight

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6
Q

effect of parabiosis on body weight in ob/ob mice?

A
  • parabiosis in the sharing of blood circulation between animals
  • connect one obese mouse with ob/ob gene and a mouse which produces leptin
  • reduces feeding and weight in obese mouse
  • shows that there must be something released from the brain to tell you to stop eating
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7
Q

leptin and eating - feedback

A

when you eat a meal, replenishing the adipose (fat stores), fat deposits increase and leptin is released into the blood, where it will act upon the leptin receptors in the arcuate nucleus to increase satiety

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8
Q

which parts of the hypothalamus play important roles in feeding and eating/weight regulation?

A

ventromedial and lateral hypothalamus

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9
Q

where is the hypothalamus located?

A

underneath the thalamus, base of the brain

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10
Q

where is the arcuate nucleus located?

A

bottom part of the third ventricle

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11
Q

how can you assess the function of a brain region?

A
  • lesion

- electrical stimulation

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12
Q

what happens to a mouse with a VMH lesion

A

it gets obese

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13
Q

what happens to a mouse with a leptin lesion

A

it gets skinny

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14
Q

what type of responses does leptin have?

A

anorexic and orexigenic

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15
Q

explain the anorexic response of leptin

A

leptin binding to receptors on the arcuate nucleus

  • there are neurones that extend from the arcuate nucleus to the lateral hypothalamus
  • these neurones release 2 peptides: CART or alpha-MSH
  • activation of these peptides inhibit the LH and therefore inhibit feeding behaviour
  • there are neurones that extend from the arcuate nucleus to the paraventricular hypothalamus - activate it and stimulate release of ACTH and TSH from anterior pituitary
  • diminish appetite
  • increases basal metabolic rates, increase sympathetic activation
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16
Q

explain the orexigenic response of leptin

A
  • CART and alpha-MSH are inhibited
  • neurones extend from arcuate nucleus to lateral hypothalamus and release 2 peptides:
  • NPY and AgRP - activated by low leptin
  • neurones extend from arcuate nucleus to paraventricular hypothalamus to inhibit TSH and ACTH release
  • LH neurones also contain MCH and Orexin
17
Q

what is the relevance of the MC4 receptor?

A

competition
alpha-MSH and AgRP both bind to the MC4 receptor
AgRP blocks the effect of alpha-MSH

18
Q

explain MCH

melanin-concentrating hormone

A
  • cell bodies are in the hypothalamus project to many different brain regions
  • widespread connections in the brain
  • prolongs consumption of food
19
Q

explain orexin

A
  • cell bodies are in the hypothalamus
  • widespread cortical connection
  • promotes meal initiation, increase feeding and appetite
  • also plays a role in wakefulness and arousal
  • decreased sleep and increased vigilance
20
Q

people with narcolepsy have…

A

…dysfunctional orexin

-narcolepsy is when you go to sleep randomly

21
Q

how does amphetamine affect orexin levels

A

increases levels in the brain dramatically

22
Q

disruption of hypothalamus regulation could lead to?

A
  • hyperphagia
  • anorexia
  • bulimia nervosa
23
Q

3 phases of feeding?

A

cephalic
gastric
substrate

24
Q

explain the cephalic phase

A

hunger

  • big secretion of saliva in mouth
  • big secretion of gastric juice in stomach in preparation for food intake
  • release of ghrelin
  • activation of NPY/AgRP containing neurones in arcuate nucleus
25
Q

removal of ghrelin secreting cells in the stomach causes what?

A

loss of appetite

26
Q

explain the gastric phase

A

feeling full

  • food gets inside the stomach, stomach expands and feels full, gastric distention - sends signals via vagus nerve to nucleus of solitatory tract for satiety to take place
  • CCK released in intestines in response to certain foods
  • insulin released by pancreatic beta cells
27
Q

what is the substrate phase?

A

nutrients move through the intestines and get absorbed into blood circulation

28
Q

how are mood and food linked?

A

5-HT in hypothalamus

  • rises in anticipation of food
  • spike during the meal
  • low serotonin levels associated with anorexia nervosa and bulimia with depression
  • certain types of food release tryptophan, precursor for serotonin eg. chocolate
29
Q

why do we eat?

A

we want food - hedonic aspect

we like food

30
Q

name things that trigger the rewards system

A

natural rewards

  • food
  • sex
  • water
  • nuturing
31
Q

what does the rewards system consist of?

A

dopaminergic neurons projecting from the VTA to the nucleus accumbens
-rewards stimulate the neurones to release dopamine

32
Q

centre of rewards in the brain?

A

nucleus accumbens

33
Q

what does amphetamine do to the rewards system?

A

hyper stimulates the rewards system

-activate mesolimbic pathway, causes bigger release of dopamine than with normal rewards

34
Q

in initial stages of addiction what happens?

A

reinforcement drives the person to carry on taking it

35
Q

explain withdrawal

A

craving of the substance/alcohol/drug
-the craving could be not so much craving to get high, but craving purely to self-medicate the withdrawal symptoms
(people want to stimulate D2 receptors)

36
Q

postive vs negative reinforcement?

A

positive means anything after a certain behaviour that makes it more likely that the behaviour will happen again
-drug administration driven by positive reinforcement

negative means behaviour is strengthened by stopping or removing a negative outcome
-withdrawal driven by negative reinforcement

37
Q

how are the role of D2 receptors in obesity investigated?

A

PET scan

  • radioactive tracer selective for the D2 receptor injected into patient
  • tracer binds to D2 receptors, which are in the reward centres of the brain
  • obese people have lower levels of D2 receptors
38
Q

a decrease in D2 receptors means what?

A

decrease in reward signalling

Neuro (21 decks)

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