PSYA3 Neural Mechanisms

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  • Neural Mechanisms
    • A01
      • Homoeostasis is the process which the body maintains a constant internal environment. It is maintained by a negative feedback loop which assumes that all body variable have a set point.
        • Each individual has a set point that their weight is regulated by, the body regulates on fat stores and glucose levels.
      • The body has two separate systems that make up the dual centre theory of feeding, that 'turn eating on and off' there are two areas of the hypothalamus involve din eating behaviour.
      • The lateral hypothalamus serves as a hunger centre where there is an increase in Ghrelin and reduction in blood glucose this induces eating.
      • The ventromedial hypothalamus contains the satiety centre, this responds to an increase of blood glucose and leptin leptin decreases ghrelin which shuts off eating.
        • However, the LH may not just be a switch got eating, when it is damaged, people suffer problems with thirst which suggests it has other roles.
      • Cognitive factors such s neural control affects our eating behaviour. Simply thinking about food can make us hungry, the cognitive aspect of food not only includes images of food but related tastes and smells.
        • The neural control of these cognitive factors probably originates from the amygdala and the inferior prefrontal cotrex
          • The Alameda is though to control the selection of food based on past experiences good or bad.
      • Kluver-brucy syndrome can be used to support damage because damage to the amygdala and the inferior pre-frontal cortex could explain the feeding abnormality observed in kluver-brucy syndrome.
        • People with this often show increased appetite, indiscriminate eating, even attempts to eat non-food items.
          • Research on the effects of damage to these areas of the brain suggests that food cues no longer accurately represent their real reward value supporting the role of the amaygdala and the IPC in eating behaviour.
    • A02
      • There is research to support the role of Leptin, leptin is an appetite suppressor released by far cells which goes to the VMH to turn off eating. Zhang found that when Leptin was injected into obese mice with leptin deficiency it caused dramatic weight loss.
        • This supports that the role of the VMH is to use leptin to turn off eating. This research has real world application as leptin could be used to treat obesity for more successfully than current treatments such as restrain theory.
      • Support for the VMH and LH in eating comes from research into damage to them. Damage to the VMH may lead to hypophagia which is the failure to stop eating when full. Also, damage to the LH may lead to aphagia which is the failure to eat when hungry. This supports the dual centre theory as controlling eating behaviour,
      • Damage to the LH may cause the production of neuropeptide Y which induces eating.
        • Wickens found that when injecting rats with NPY it caused tgem to start feeding immediately even when full. This suggests that NPY has a role in feeding and supports the role of the LH in eating behaviour.
          • However, Marie questioned the role of NPY as she modified mice with no NPY and had no trouble feeding but, this may be due to the modification of the mice thus disputing the findings to her study.
      • There are limitations of the homoeostasis explanation because  for the hunger mechanisms to be adaptive it must be both anticipated and prevented by energy deficits not just to react to them.
        • As a result, the theory that hunger and eating are triggered when energy resources fall below the desired level is compatible with real life. For such mechanisms to be adaptive, it must promote levels of consumption that maintain bodily resources well above optimum level.
      • Rolls + Rolls found that removing the amygdala from rats caused them to eat familiar and unfamiliar foods indiscriminately, unlike amydala intact rats who avoided novel foods.
      • The dual centre is a biological approach is reductionist as it reduces complex eating behaviours to simple on/off switches.
      • It is also deterministic as it focuses on the role of nature and ignores factors such as mood and culture which makes it a limited explanation.


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