Neural And Hormonal Mechanisms Of Eating

Question 1

Homeostasis

Answer 1

• a negative feedback loop; all body variable have a set point
• the process by which the body maintains a constant internal environment
• digestive tract and hypothalamus play a significant role in eating behaviour
• weight is based on a set point, body regulates hunger from;
• lipostatic hypothesis; fat stores
• glucostatic hypothesis; blood sugar levels
• ATP; cellular energy

Question 2

The dual centre theory of feeding behaviour

Answer 2

• x2 areas of the hypothalamus
• Ventro Medial Hypothalamus/ VMH -> satiety centre
• Lateral Hypothalamus/ LH -> hunger centre

Question 3

Lateral hypothalamus

Answer 3

• deteceds glucose levels in liver
• when blood drops below a certain levels, LH activates
• triggers people to feel hungry and motivate to eat

Question 4

Role of Ghrelin

Answer 4

• secreted by stomach
• more is released the longer we go without food
• levels go up before we eat and down 3 hours after a meal
• detected by hypothalamus, sent to LH causing NPY to increase

Question 5

Evidence for role of LH

Answer 5

• An & Brobeck: investigated LH by lesioning levels in rats
• they stopped eating (aphasia), suggesting the role of LH is to switch on eating
• Russek: starved rats before letting them feed
• injected glucose into liver; stopped feeding ->proves LH triggers people to feel hungry

Question 6

Ventral medial hypothalamus

Answer 6

• hungers off switch
• levels of glucose stored in liver as glycogen
• detected by cells in VMH
• glucose levels rise above a certain point, VMH is activated
• LH inhibited -> individual becomes satiated

Question 7

Role of leptin

Answer 7

• a hormone secreted by adipose cells
• levels of leptin in blood and fat levels increase, detected by VMH
• leptin -> appetite suppressant
• binds to receptors in hypothalamus to counteract effect of NYP
• increased sympathetic NS, to stimulate fatty tissue to transfer energy

Question 8

Evidence for role of VMH

Answer 8

• Hetherington and Ranson: by liesing the levels of VMH in the rats caused them to overeat and become obese, shows VMH is responsible for feeling of fullness

Question 9

Oversimplifed models

Answer 9

• Valassi et al: highlights the role of CCK, a horse on produced in the duodenum, activates the nerve that sends signals from the GI tract to the hypothalamus which contributes to the stop eating mechanism