Anorexia: Neural mechanisms

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  • Created by: izzy89
  • Created on: 09-12-15 17:23

Serotonin

Serotonin

  • High levels of serotonin have been linked to appetite suppression
  • Serotonin is thought to activate melanocortin-4 receptors, which curbs hunger
  • It blocks neurons that increase appetite 
  • It could be suggested that anorexics have especially high levels of serotonin

AO2

  • Serotonin injections: shown to exert a continued appetite supression
  • Stimulates obssesive behaviour: this is behaviour typically shown in AN sufferers
  • Diet drug Fen-Phen: Increases serotonin activity in the brain to suppress appetite
  • However, suffers from 'Treatment Actiology Fallacy', just because it facillitates weight loss does not mean that it is involved in anorexia 
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Dopamine

Dopamine

  • Responsible for transmitting reward signals withing the brain
  • Suggested there are several different version of the gene which controls how many dopamine receptors we have
  • People with genetically more dopamine are less motivated to eat less food because they only need a bit to gain pleasure 
  • Suggested that AN sufferers have this

AO2

  • Kaye et al: PET scans tracked dopamine levels, found that after a dose of amphetamines AN sufferers reported anxiety, whereas control group felt pleasure
  • Castro-Fornieles et al (2006): Adolescent girls with AN had a higher level of homovanillic acid (dopamine waste product) and improvement of weight was associated with a normalisation of homovanillic acid
  • Cannot be sure: May actually be starvation thta causes high levels of dopamine or there could be a third variable involved 
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Hypothalamus

Hypothalamus

  • LH could be damaged which causes the VMH to become over-activated in response
  • Hunger is therefore constantly supressed and leads the body to believe it is overweight
  • Encourages the individual to reduce their food intake

AO2

  • Aphagia research: Damaged LH stops the feeling of hunger and leads to less feeding in rats (Anand & Brobeck, 1951)
  • However, no dmaged LH has been found in post-mortems of AN sufferers
  • Simplistic: Suggests that te LH has to be damaged, however it could be the other way round
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Prenatal

Prenatal

  • Hypoxia (a lack of oxygen) during birth can cause complications
  • As well as this, infections during pregnancy can affect the brain development of the feotus, particularly in the 2nd trimester

AO2

  • Favaro et al (2006): Found a significant association with risk of developing AN and obstructionn of the blood supply in the placenta
  • Eagles et al (2001): Thought people with AN are more likely to hav had their 2nd trimester in the winter which would expose them to more infections
  • Additionally, AN sufferers tend to have older siblings, more children during pregnancy= more exposure to infections
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IDA

AO2

  • Reductionism
  • Can't explain AN sufferers experiance of body distortion
  • Implies that anorexics are never hungry, eve though they often cite hunger as a motivation in continuing to starve themselves
  • Suggests that it is more to do with a maladaptive response to hunger
  • Alternative Approaches
  • Dramatic increase of AN suggests environmental factors would better explain it
  • For example, behavioural/SLT approach
  • Role models are famed for thin bodies
  • Vicarious reinforcement
  • Cross-culturally, rates are dramaticallt different which siggests that it is environmental
  • On the other hand, difference could be due to a difference of doctore's ability to diagnose it
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