Neural Mechanisms

Question 1

What explanations does the role of neural mechanisms come under?

Answer 1

Biological and evolutionary explanations

Question 2

What is the main reason as to why we eat?

Answer 2

Homeostasis

Question 3

What does homeostasis mean?

Answer 3

Maintaining a constant internal environment

Question 4

Explain homeostasis in relation to eating behaviour

Answer 4

Homeostasis detects the state of internal environment and homeostasis corrects the state of the internal environment - it is maintained via a negative feedback loop: assumes all body variables have a set point or range

Question 5

How many separate systems has the body developed for neural mechanisms?

Answer 5

2 - one for turning eating on and one for turning it off

Question 6

What plays the most important role in producing feelings of hunger?

Answer 6

A decline in blood glucose levels activates part of the brain called the lateral hypothalamus, resulting in the feeling of hunger

Question 7

What happens when an individual consumes food?

Answer 7

This causes glucose levels to rise again which activated the ventromedial hypothalamus, leading to feelings of satiation, which in turn inhibits further feeding

Question 8

What is the main disadvantage to homeostasis in the role of neural mechanisms?

Answer 8

Only reacts to energy deficits, so if homeostasis was adaptive, should be ready to prevent loss of energy before it occurs - the theory hunger and eating triggered only when energy resources fall below desired level is incompatible with harsh reality in which such systems would have evolved - for mechanism to be truly adaptive, must promote levels of consumption that maintain bodily resources well above the optimal level to act as a buffer against future lack of food availability

Question 9

What is the counterpoint for the main disadvantage of homeostasis in the role of neural mechanisms?

Answer 9

Is this a fair criticism? Actual behaviour of most humans is to snack all day if they have resources and time, so is homeostasis a mechanism to encourage snacking or grazing?

Question 10

Name and explain another main evaluative point about homeostasis in the role of neural mechanisms

Answer 10

May be masked by demand of other human activities - when stressed, produce extra ghrelin and ghrelin is part of the body’s natural defence against stress as reduces depressive and anxious behaviours - ghrelin also boosts appetite leading to increased comfort eating and thus homeostasis would be overridden by this stress response

Question 11

What are the 2 hormones released from the pancreas?

Answer 11

Insulin & glucagon

Question 12

Outline the role of insulin in the role of neural mechanisms

Answer 12

Insulin controls blood glucose by allowing it to enter cells from the bloodstream and it also converts glucose to glycogen (stored in the liver, muscles, fatty tissues and makes up the main energy reserve for the body) - insulin also allows fats in bloodstream to be stored in fat or adipose cells - adipose cells make up fatty tissue of our body and are another key energy reserve - this affects our body weight

Question 13

How do we know that the hypothalamus plays a role in eating and I weight gain and loss?

Answer 13

Patients with tumours in the hypothalamus tend to become obese

Question 14

What are the 2 separate systems in the body which help t control eating?

Answer 14

1) Lateral hypothalamus

2) Ventromedial hypothalamus

Question 15

Explain what the lateral hypothalamus is

Answer 15

An area of the hypothalamus which contains the feeding centre which initiates or starts eating behaviour - responds to decreased blood glucose and an increase in ghrelin which is a hormone released from the stomach when it is empty - researchers discovered damage to the LH in rats caused Aphagia (absence of eating) and stimulation elicits feeding behaviour

Question 16

Name the 4 studies supporting the role of the lateral hypothalamus

Answer 16

1) Anad & Brodeck (51)
2) Stellar (54)
3) Neuropeptide Y - NPY
4) Stanley (86)

Question 17

Outline Anad & Brodeck (51)

Answer 17

Aphagia can be caused by damage to LH in rats

Question 18

Outline Stellar (54)

Answer 18

Stimulation of the LH causes eating behaviour in rats - these opposing effects of injury and stimulation led researchers to conclude they had discovered the ‘on switch’ for eating

Question 19

Outline Neuropeptide Y (NPY)

Answer 19

Particularly important for switching on eating - when injected into hypothalamus of rats, NPY causes them to immediately begin feeding even when satiated (Wickens 00)

Question 20

Outline Stanley (86)

Answer 20

Found repeated injections of NPY leads to obesity in rats in a matter of days

Question 21

Explain what the ventromedial hypothalamus is

Answer 21

Contains the satiety centre which signals when you are full which inhibits eating - responds to increase in blood glucose, a decrease in ghrelin and to CCK (hormone released when food detected in the duodenum or the first part of the small intestine) - also responds to leptin, long-term satiety signal released by fat - damage to the VMH caused rats to overeat leading to hyperphagia and stimulation inhibited feeding

Question 22

Name the 4 evaluative points for neural mechanisms

Answer 22

1) Issues with LH being the on switch for eating
2) Marie (05) - NPY
3) Role of the VMH - Gold (73)
4) Teitalbaum (57)

Question 23

Explain the issues with LH being the on switch for eating

Answer 23

Damage to the LH caused deficits in other aspects of behaviour (thirst and sex) rather than just hunger - also, research show eating behaviour controlled by neural circuits run throughout the brain, not just by hypothalamus - Sakurai (98) although LH plays important role, not brain’s eating centre

Question 24

Outline Marie (05) in relation to neuropeptide Y

Answer 24

Bred mice who did not produce NPY and found no subsequent decrease in feeding behaviour, however, injections of NPY did cause hunger in mice - this effect may be due to experimental conditions because of the unexpected intake of NPY in experiment

Question 25

Outline Gold (73) in relation to the role of the VMH

Answer 25

Found lesions only in the VMH on own did not result in hyperphagia - damage to nerve fibres passing through VMH tends to also damage anther area of the hypothalamus, the paraventricular nucleus, PVN - not believed damage to the PVN alone causes hyperphagia - PVN also detects specific foods our body need and consequently seems to be responsible for cravings - however, subsequent research has failed to replicate these findings

Question 26

Outline Teitalbaum (57)

Answer 26

Lesions to the VMH should increase appetite and motivation to eat and increase food intake, but found this not the case and instead rats became lazy and very fussy about food on offer - they would not eat food that was stale or food with quinine added, but normal rats would

Question 27

Outline neural control of cognitive factors

Answer 27

It is not uncommon to think about food and become hungry - this is the cognitive aspect of food including images, sights and smells of food - the neural control of these cognitive factors in hunger probably originates in 2 main brain areas: amygdala and the inferior prefrontal cortex

Question 28

What are the 2 main brain areas for the neural control of cognitive factors?

Answer 28

1) Amygdala

2) Inferior prefrontal cortex

Question 29

Explain what the amygdala is

Answer 29

Role is selection of foods on basis of previous experience

Question 30

What study supports the existence and role of the amygdala in the neural control of cognitive factors?

Answer 30

Rolls & Rolls (73)

Question 31

Outline Rolls & Rolls (73)

Answer 31

Found surgically removing amygdala in rats would cause animals to consume both familiar and unfamiliar foods indiscriminately - whereas amygdala-intact rats would initially avoid unfamiliar foods and consume only more palatable familiar food instead

Question 32

Explain what the inferior prefrontal cortex is

Answer 32

Receives messages from part of the brain responsible for smell - as odours influence taste of foods, damage to IPC thought to increase eating as diminished sensory responses to food odour, and also probably to taste

Question 33

Name 2 positive evaluative points for the neural control of cognitive factors

Answer 33

1) Kluver-Bucy Syndrome

2) Zald & Pardo (97)

Question 34

Explain the Kluver-Bucy Syndrome

Answer 34

Damage could explain feeding abnormalities observed in KB syndrome - patients typically show increased appetite, indiscriminate eating and attempts to eat non-food items - research on effects of damage to brain areas suggests food cues no longer accurately represent their real reward vale to individual

Question 35

Outline Zald & Pardo (97)

Answer 35

Provided physiological evidence to support claim that amygdala participates in emotional processing of smelling stimuli in brain - exposed healthy ppts to aversive smell stimuli while measuring blood flow to amygdala by PET scan - exposure to unpleasant odours produced significant blood flow increase to amygdala whereas non-aversive odours did not cause increased blood flow - increased blood flow to amygdala also associated with subjective ratings of perceived unpleasantness of stimuli

Question 36

What main study provides support for the role of ghrelin in eating behaviour.

Answer 36

Cummings (04)

Question 37

Outline Cummings (04)

Answer 37

Monitored ppts’ ghrelin levels every 5mins and assessed hunger levels every 30mins - found 5/6 significant correlation between ghrelin levels, emptiness of stomach and hunger - shows support for the role of ghrelin in eating behaviour

Question 38

Name and explain 2 negative points about Cummings (04)

Answer 38

1) Small sample limiting how far findings can be generalised and likely ppts’ subjective judgement of hunger were influenced by expectations of food based on meal times (cultural factors)
2) Self-reports subject to bias

Question 39

Name a positive evaluative point about Cummings (04)

Answer 39

Further support comes from injections of ghrelin which resulted in increased food intake in animals and humans but also, gastric bands used to treat obesity reduce ghrelin secretion

Question 40

Name 2 general negative evaluative points about the neural control of cognitive factors

Answer 40

1) Hunger and eating may not be purely under neural control

2) Evolutionary approach

Question 41

Explain how hunger and eating may not purely be under neural control

Answer 41

Lutter (08) shown body produces extra quantities of hormone ghrelin in response to stress - part of the body’s natural defence against stress as reduces depressive and anxious behaviours typically associated with stressful situations - however ghrelin also boosts appetite, leading to increased comfort-eating - suggests blocking body’s response to ghrelin may help people with a tendency to comfort-eat to control their weight - however approach may be problematic as it would reduce ghrelin’s beneficial effects as part of response to stress

Question 42

Explain why the evolutionary approach is a negative point for the neural control of cognitive factors

Answer 42

If decline in body’s energy resources below optimal level not major cause of hunger then what is? Evolutionists suggest primary stimulus for hunger and eating is food’s positive-incentive value (people eat as normally develop a relish for particular tastes that are in nature associated with foods that promote our survival)

Question 43

What is a general positive point about the neural control of cognitive factors

Answer 43

Real-world application

Question 44

Explain the real-world application of the neural control of cognitive factors

Answer 44

Research suggests NPY has important role in eating behaviour - suggests one main reasons why overweight people continue to eat too much is because brain produces NPY in excessive amounts, telling individual they’re constantly hungry - however Yang (80) showed NPY also produced by abdominal fat - researchers suggest this leads to viscous cycle where NPY produced in brain leads to more eating and production of more fat cells which in turn produces more NPY and more fat cells and so on - by targeting individuals at risk of increased levels of NPY, Yang believes it should be possible to treat them with drugs that turn off NPY and thus prevent obesity