Bio. Explanations of Eating - Neural Factors

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  • Created by: rhallett
  • Created on: 11-12-15 23:30
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  • Biological Explanations of Eating Behaviour - Neural Mechanisms
    • The brain controls eating behaviour to maintain homeostasis in the body of essential nutrients like glucose.
    • Hypothalamus
      • One theory was that areas in the hypothalamus controlled eating behaviour. The lateral hypothalamus was said to contain the feeding centre and trigger eating when blood glucose is low
        • The ventro-medial hypothalamus was said to contain the satiety or fullness centre which inhibits eating behaviour when are full and responds to an increase in blood glucose
          • Both areas also respond to chemical messengers such as Neuropeptide Y and Ghrelin
      • +Research on Rats: 1) If lateral hypothalamus was damaged they stopped eating and lost weight; suggesting LH triggers eating
        • -However, research on rats might not apply to humans because they have a different biology and their eating behaviour is less influenced by social factors, also unethical as the rats are being harmed
      • +Research on Rates: 2) If the ventromedial area of the hypothalamus was destroyed, rates overate and became obese; suggesting this area contains the brain's fullness centre
        • -However, research on rats might not apply to humans because they have a different biology and their eating behaviour is less influenced by social factors, also unethical as the rats are being harmed
      • +Electrical stimulation of the VMH in rats inhibits (prevents) feeding whilst simulation of the LH produces feeding
      • +Human research: tumours in this area of the brain can cause reduced appetite and produce anorexic-like symptoms in humans eg. Lewin reports the case of a NZ nurse (1972) who had lost weight and was found to have a tumour in her LH
        • -Later research showed that the LH and VMH were not just eating and fullness centres. Eg. damage to the LH prevents other behaviours as well, such as sex and drinking; not just a hunger centre.
    • Neurotransmitters & Hormones
      • A number of neurotransmitters and hormones also play a part in regulating eating behaviour by acting on areas of the brain
      • LEPTIN - Hormone produced by fat cells. .
        • When the body is carrying lots of fat, high levels of Leptin are produced which reduces appetite and food intake. Has an anorexigenic effect by acting on neurons in the arcuate nucleus of the hypothalamus
        • +Mice with genetic mutations (eg the obsese gene) can't produce Leptin or respond to it and become obsese
        • +Farooqi describes the case of a child who was extremely obese, due to having a genetic mutation affecting Leptin
          • This research has an obvious practical application as it suggests that obese people could be treated with Leptin, and this has been effective in some cases
      • DOPAMINE- an NTM which allows animals to feel pleasure.
        • Released in the pleasure centres of the brain such as the ventral striatum ad motivates eating behaviour
        • +Volkow found evidence that a person's dopamine system affected their food intake. Used PET scans and showed that obese people had fewer dopamine receptors in the ventral striatum than did healthy weight controls. Suggested this was because people with reduced dopamine activity may eat more to compensate
        • +The NTM Neuropeptide Y is also thought to stimulate eating -eg, if ti is injected into the hypothalamus of rats it causes them to eat even if they are satiated

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