Neural And Hormonal Mechanisms In Eating Behaviour

Question 1

Briefly describe neural mechanisms into eating behaviour.

Answer 1

• hypothalamus: dual feeding centre theory
• neural mechanisms are important in hunger and satiety
• homeostatic - strive to maintain fixed amount of energy sources
• reducing amount of food in body by using glucose and fats triggers desire to eat to top up
• eg liver detects lower glucose so sends signal to brain

Question 2

How does the lateral hypothalamus work?

Answer 2

• feelings of hunger
• cells detect low glucose in liver activating LH
• neurotransmitter called neuropeptide Y (NPY) produces stimulating LH

Question 3

How does the ventromedial hypothalamus work?

Answer 3

• satiety
• glucose levels rise when feeding starts and VMH detects this
• VMH triggered when levels go above a certain point
• LH inhibited

Question 4

Evaluate neural mechanisms into eating behaviour.

Answer 4

S - lesion on LH in rats = aphagia, giving them NPY = excessive eating, lesion on VMH = hyperphagia.
C - can’t extrapolate because of cultural and social factors. simplistic - dopamine and serotonin involved. Lesions may damage other areas.

Question 5

How is ghrelin a mechanism in eating behaviour?

Answer 5

• made by stomach cells
• indicates amount of time since last eaten
• ghrelin rises as stomach empties
• when it rises above a certain point, receptors in arcuate nucleus detect this and start to secrete NPY = hunger

Question 6

How is leptin a mechanism in eating behaviour?

Answer 6

• fat cells
• increases as fat reserves increase
• VMH detects leptin
• high levels leptin = high fat reserves = appetite suppressed
• blocked the action of NPY so no hunger.
• fat reserves fall = LH triggered

Question 7

Evaluate hormonal mechanisms in eating behaviour.

Answer 7

S - 9 volunteers in double blind study injected w saline or ghrelin, and again a week later. Hunger assessed by how much ate at a buffet. 30% increase in mean values in ghrelin condition. FMRI scans showed those injected w ghrelin has more activity in areas of brain associated w visual responses to food when shown pics of food 3 hours after a meal. Humans w no leptin = obese
C - leptin deficiency not only cause - leptin resistance means can’t produce satiety levels - 20-30x more needed to increase weight loss
I - biological reductionism (only eat when hungry only stop when full) ignores other factors
P - leptin replacement therapy - 18 month study found 40% weight loss in people given leptin - good for NHS