motivation

Question 1

what is motivation?

Answer 1

driving force
physical need
wanting (hedonic aspect)

Question 2

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

Answer 2

• endocrine system
• ANS
• emotions and drive

Question 3

what is catabolism?

Answer 3

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

Question 4

what is the opposite of catabolism?

Answer 4

anabolism

-glucose being stored

Question 5

what is there long term regulation of?

Answer 5

body weight

Question 6

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

Answer 6

• 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

Question 7

leptin and eating - feedback

Answer 7

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

Question 8

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

Answer 8

ventromedial and lateral hypothalamus

Question 9

where is the hypothalamus located?

Answer 9

underneath the thalamus, base of the brain

Question 10

where is the arcuate nucleus located?

Answer 10

bottom part of the third ventricle

Question 11

how can you assess the function of a brain region?

Answer 11

• lesion

- electrical stimulation

Question 12

what happens to a mouse with a VMH lesion

Answer 12

it gets obese

Question 13

what happens to a mouse with a leptin lesion

Answer 13

it gets skinny

Question 14

what type of responses does leptin have?

Answer 14

anorexic and orexigenic

Question 15

explain the anorexic response of leptin

Answer 15

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

Question 16

explain the orexigenic response of leptin

Answer 16

• 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

Question 17

what is the relevance of the MC4 receptor?

Answer 17

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

Question 18

explain MCH

melanin-concentrating hormone

Answer 18

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

Question 19

explain orexin

Answer 19

• 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

Question 20

people with narcolepsy have…

Answer 20

…dysfunctional orexin

-narcolepsy is when you go to sleep randomly

Question 21

how does amphetamine affect orexin levels

Answer 21

increases levels in the brain dramatically

Question 22

disruption of hypothalamus regulation could lead to?

Answer 22

• hyperphagia
• anorexia
• bulimia nervosa

Question 23

3 phases of feeding?

Answer 23

cephalic
gastric
substrate

Question 24

explain the cephalic phase

Answer 24

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

Question 25

removal of ghrelin secreting cells in the stomach causes what?

Answer 25

loss of appetite

Question 26

explain the gastric phase

Answer 26

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

Question 27

what is the substrate phase?

Answer 27

nutrients move through the intestines and get absorbed into blood circulation

Question 28

how are mood and food linked?

Answer 28

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

Question 29

why do we eat?

Answer 29

we want food - hedonic aspect | we like food

Question 30

name things that trigger the rewards system

Answer 30

natural rewards - food - sex - water - nuturing

Question 31

what does the rewards system consist of?

Answer 31

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

Question 32

centre of rewards in the brain?

Answer 32

nucleus accumbens

Question 33

what does amphetamine do to the rewards system?

Answer 33

hyper stimulates the rewards system | -activate mesolimbic pathway, causes bigger release of dopamine than with normal rewards

Question 34

in initial stages of addiction what happens?

Answer 34

reinforcement drives the person to carry on taking it

Question 35

explain withdrawal

Answer 35

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)

Question 36

postive vs negative reinforcement?

Answer 36

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

Question 37

how are the role of D2 receptors in obesity investigated?

Answer 37

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

Question 38

a decrease in D2 receptors means what?

Answer 38

decrease in reward signalling