Eating behaviours essay

Question 1

Role of Ghrelin

Answer 1

• A hormone secreted by the stomach which increases appetite when hungry (an appetite stimulant)
• A hormonal marker of how long since we have last eaten because the amount produced is closely related to how empty our stomach is
  – more ghrelin is released the longer we go without food

Question 2

Role of Leptin

Answer 2

• A hormone produced by adipose (fat) cells that decreases appetite as we have enough stored energy
• Levels of leptin in the blood increase along with fat levels & these are detected by the brain by the Ventro-medial hypothalamus (VMH)
• Tells the hypothalamus that we have enough fat and we can eat less/ stop eating; helps to regulate energy balance by suppressing food intake

Question 3

The dual- centre model of eating

Answer 3

• Lateral hypothalamus (LH) = the ‘feeding center’ of the hypothalamus, containing cells that detect glucose levels in the liver. The LH
  is activated when glucose levels fall BELOW a certain level – causing the individual to become hungry & triggering the motivation to eat
• Ventro-medial hypothalamus (VMH) = the ‘satiety centre’ of eating behaviour. Levels of glucose circulating in the bloodstream and stored in the liver (as glycogen) are detected by cells in the VMH. Activity in the VMH is triggered once glucose levels reach a set point, with LH activity inhibited at the same time. The individual therefore becomes satiated; they feel full & stop eating.

Question 4

Zhang [1994]

Answer 4

OB/OB mice injecting them w. leptin = weight loss = signalled ideal weight so stopped eating = supporting the role of Leptin
Highlights the importance of leptin and may provide potential treatment for clinically abnormal, behvaiours. in the future = very important.

Question 5

Hetherington + Ranson - Rat study

Answer 5

Lesion rat study = strategical wounds = various areas of the brain VMH damage = obese and LH damage = eating problems. Reductionist approach not humans and isn’t generlisable to human as cuts aretn 100% precise and might cut different parts of the brain = confounding variable and results can’t be linked to LH and VMH directly

Question 6

Real-life Application - Lincio et al [2004]

Answer 6

genetic condition where they can’t produce leptin naturally, associated with severe obesieity. Leptin replacement therapy = 40% weight loss + 49% reduction in eating.