Neural + Hormonal mechanisms

Question 1

Homeostasis

Answer 1

Mechanism that maintains a stable and constant internal environment; detects if the body has enough nutrients and if not ,corrects this

Question 2

Turning food ON

Answer 2

One system the body has is for turning food ‘on’ where when glucose levels are low hunger increases which activates the lateral hypothalamus (LH) to create feelings of hunger to eat and rise levels again

Question 3

Turning food OFF

Answer 3

Once glucose levels rise again this activates the ventromedial hypothalamus which creates satisfaction to inhibit further feeding

Question 4

Lateral hypothalamus research

Answer 4

• Began in 1950s when researches found damage to the LH in rats caused aphagia
• Stimulation of LH elicits feeding behaviour which led to the discovery of switch on for eating

Question 5

Neuropeptide Y

Answer 5

Neurotransmitter found in the hypothalamus which is important for turning on eating
Stanley found repeated injections of NPY into hypothalamus of rats produces obesity

Question 6

Ventromedial hypothalamus

Answer 6

• Opposite effects; damage to VMH caused rats to over eat leading to hyperphagia
• Stimulation inhibited feeding suggesting it stops eating due to glucose receptors

Question 7

Paraventricular nucleus

Answer 7

• Damage to nerve fibres passing through VMH also damages the area of the hypothalamus called the paraventricular nucleus
• Damage to this area alone can cause hyperphagai (Gold)
• Also detects specific foods our body needs + responsible for our cravings

Question 8

Hormonal mechanisms

Answer 8

• 2 main hormones in controlling eating; Ghrelin(increases appetite) and Leptin(decreases)
• Maintains our body weight at an optimal level by working together
• Both peripheral signals with central effects

Question 9

Ghrelin

Answer 9

It is released into the stomach + stimulates the hypothalamus ; when bodily resources are low/ under eating gherelin levels increase
-Play a role in determining how quickly we feel hungry after eating ; levels raise high before we eat and go down again for about 3 hours after a meal

Question 10

Obesity

Answer 10

Ghrelin has been important in the development of obesity as stimulating appetite leads to an increase in body weight

Question 11

Research

Answer 11

Ghrelins role in appetite control was first discovered when injected into the blood stream of rats , stimulated food intake.

Question 12

Leptin

Answer 12

Normally produced by fat tissue + secreted into bloodstream then travel to the brain
-Circulating leptin acts as a long term signal of amount of fat stored while short term fluctuations in levels give information on changes in calorific intake

Question 13

2 major functions

Answer 13

1. By binding receptors in the hypothalamus it counteracts the effects of neuropeptide Y
2. Increases sympathetic NS activity which stimulates fatty tissue to burn energy

Question 14

Research

Answer 14

Researchers noticed when they administered a new substance to genetically altered obese mice they lost weight becoming known as the substance leptin

Question 15

*Evaluation

Limitation of homeostasis

Answer 15

For a hunger mechanism to be adaptive it must be able to anticipate energy deficits not just react to them therefore the theory that hunger + eating is triggered only when energy levels fall below a desired level is not reality
An adaptive mechanism would promote consumption to maintain bodily resources above the optimum level for the future lack of food availability

Question 16

Problems with LH

Answer 16

The view that it is an on switch for eating has a few problems for example damage to the LH caused deficits in other aspects of behaviour rather than just hunger + other research has shown eating behaviour is controlled by neural circuits that run through the brain not just the hypothalamus showing it is not actually the brains ‘eating centre’

Question 17

Research support for Ghrelin

Answer 17

Wren et al conducted a double blind study of 9 healthy volunteers - either received intravenous ghrelin or saline infusion + one week later the same pps took the other condition
Was measured in terms of amount of food taken and consumed at a free choice buffet ; results showed a significant increase in food consumption in ghrelin condition compared to saline infusion with a mean difference of about 28%