Eating behaviour Flashcards
What can behaviour be?
1) Consious
- eg. writing lecture notes
2) Unconcious
eg. reflex movement from pain
What is leptin?
A protein released by fat cells to:
- Decrease eating behaviour
- Increase energy expenditure
- Can be used to reverse obesity in mice
What does high levels of leptin do?
- Activates receptors on neurons in the arcuate nucleus in the hypothalamus which contains the neurotransmitters alpha-MSH and CART
What is catabolism?
The breaking down of macromolecules for energy usage
What is the ‘hunger centre’ in the brain?
The lateral hypothalamus
What happens if anabolism > catabolism?
Obesity
What is the W/C model for motivation?
- Motivation is like water filling up the cistern
- Water filling up - increase in motivation
- Flushing releases behavior and motivation is low
- Gradually motivation builds up again until there needs to be another release
How do some foods produce change in mood?
- Carbohydrates elevate serotonin levels
- During stress, typical to see carbohydrate-rich feeding
What does decreasing levels of leptin cause?
1) Stimulates OTHER neurons in the arcutate nucleus which contain NPY (neuropeptide Y) and AgRP
2) Switches off the effects of alpha-MSH and CART
What is motivation?
The driving force behind a behavior can be:
Simple - the need to urinate, eat or drink
Complex - need to sing and dance when happy
Where do the activated neurons in the arcuate nucleus project to and cause what to happen?
1) Lower brain stem and upper spinal cord
- Activates them and increases sympathetic activity
- Causing increase in body temp and BMR
2) Paraventricular nucleus of the hypothalamus
- P nucleus projects to endocrine organs
- Stimulation of P nucleus causes release of TSH and ACTH
- Act on the thyroid and adrenal gland to increase BMR
3) Lateral hypothalamus
- Feeding behaviour inhibited by somatic motor activity
What did bilateral lesions of a rat’s ventromedial hypothalamus cause?
Overeating and obesity
What are the short-term factors which influence daily food intake?
- Cultural pressures
- Meal times
- When we last ate
- How much we last ate
How are human behaviours complicated when it comes to motivation?
1) Probability and direction of a behaviour will vary with the driving force (motivation)
2) Motivation may not guarentee a behaviour (due to social, cultural influences)
3) Balance conflicting motivations (eg. go to a lecture or go and play cricket)
What does NPY and AgRP do?
Released in respose to falling leptin levels:
1) Inhibit TSH and ACTH
2) Activate parasympathetic nervous system
3) Stimulate feeding behaviour
What are ‘anoretic peptides’?
- Appetite supressors
- Injection of a-MSH and CART mimic the effect of raised leptin levels
What do satiety signals do?
Terminate feeding and inhibit future feeding
What did Coleman propose?
That a soluble factor in obese mice (from the ob gene) fooled the brain into thinking fat levels were normal - mouse continued to eat
What does prozac do?
- Elavates serotonin levels and can relieve depression and bulimia
- Elevating serotonin levels can inhibit appetite
In the process of eating, what is the motivation and what is the behaviour?
- Motivation is hunger
- Behaviour is eating
What does gherelin do?
It is released into the blood stream from an empty stomach
- Stimulates NPY and AgRP release
- Stimulates feeding behaviour
What is anabolism?
The building up of macromolecules for energy storage
What to leptin happens during times of starvation and what does this cause?
Leptin deficiency:
- Stimulates eating behaviour
- Reduces energy expenditure
- Reduces reproductive competence
What modifies the long-term regulation of feeding (leptins)?
- Short-term signals that are generated as we eat
- Satiety signals are produced during eating and initial digestion
What is hedonistic motivation?
Enjoying food/eating
What are examples of satiety signals?
- Distension of the stomach
- Cholecytokinin
- Insulin
What are orexigenic peptides?
- Appetite stimulant
- NPY and AgRP
What is behaviour?
The response of an organism to a stimulus
Where is eating behaviour controlled?
The hypothalamus
What did incision of both sides of a rat’s lateral hypothalamus cause?
Anorexia
What did Kennedy propose?
Lipostatic hypothesis - the brain monitors and maintains fat levels
- Signal from the fat tissue to the brain hypothesised to tell the brain about fat levels
How does the need for energy change?
Depending upon:
- Time of day
- Time of month
- Time of year
- Time of life
- Level of activity
- State of health
What is the ‘satiety (fullness)’ centre in the brain?
The ventromedial hypothalamus
What happens is catabolism > anabolism?
Starvation
