Eating Behaviours (biological exp): Neural Mechanisms

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Define the key term: 'Homeostasis'
maintenance of a constant internal environment e.g. try to keep body temperature at 98 degrees Fahrenheit in various ways.
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What 3 things influence the brain to decide whether we are satiated or hungry?
The stomach, the hypothalamus and hormones.
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Who did the study which showed the influence of 'stretch receptors'?
Cannon and Washburn.
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What did Cannon & Washburn do?
Washburn swallowed a deflated a balloon which was then inflated to measure stomach contractions w/ his hunger- trying to see if the presence of food (inflated balloon) was linked to people feeling hungry or sated.
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What did they find?
Washburn felt hungry when the balloon was flat and sated when it was inflated, so the stomach muscles (stretch receptors) being stretched send a signal to the brain of 'satiation'.
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Evaluate Cannon and Washburn.
+ lab experiment, highly controlled= high internal validity, cause and effect established. - = people who had part/all of their stomach can still control their intake (stomach important but not the only thing to regulate), 1 person= difficult to gen.
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What hormone does the stomach release and what does it do?
Ghrelin- it is directly proportional to how empty the stomach is- if you inject people with ghrelin they increase food intake and body weight- ghrelin tells the hypothalamus to start eating.
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What study is used to support Ghrelin as a key factor in hunger receptors?
Cummings et al.
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What did Cummings et al. do?
6 p's ate lunch & then had ghrelin levels measured every 5 mins, p's assessed their hunger every 30 mins until p's asked for evening meal- wanted to look at blood ghrelin level changes over time.
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What did they find?
Ghrelin levels fell to lowest level straight after lunch for about 70 mins, then slowly rose peaking when P's asked for eve. meal. 5/6 p's ghrelin levels were closely correlated with degree of hunger reported.
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Evaluate Cummings et al.
+ = lab experiment, high int. validy, p's isolated from time cue so ghrelin change due to hunger not learned response - = small sample size, gender bias (males), correlational not causal, ethics: unpleasant for p's (but + = fully informed volunteers)
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What hormone is the opposite of ghrelin?
Cholecystokinin (CCK)
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Where is it/ What does it do?
Produced by small intestine once food has passed through stomach & stops you feeling hungry & stops the stomach from producing anymore acid.
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What proof is there?
If injected into rats it causes weight loss but animals with a genetic mutation that eliminates CCK system become obese.
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How is research carried out to find out if the hypothalamus is linked to feeding?
lesioning hypoth. of animals, investigate change in feeding after damage to mid-brain, effects of neurotransmitters in mid-brain, impact of drugs on mid-brain, use of functional magnetic resonance imagery (FMRI).
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What are the 2 parts of the hypothalamus linked to?
Lateral Hypothalamus linked to the feeding centre and the ventromedial hypothalamus was the satiety centre.
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What researchers lesioned the Lateral Hypothalamus and what happened?
Anand & Broebeck- loss of feeding behaviour (aphagia), rats stopped eating even in the presence of food.
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What researchers lesioned the Ventromedial Hypothalamus and what happened?
Hetherington & Ranson- rats overrate and got dramatically obsese (hyperphagia).
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Evaluate the use of animals in Neural Mechanism studies.
+ = small and easily caged, cheaper, similar enough to humans to generalise, fewer restrictions to researchers: better than doing it on humans (ethics). - = unethical, generalisability still hard, irreversible damage, no consent.
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What are the debates with Neural Mechanisms?
Reductionist: simplistic, doesn't acknowledge social meanings of eating. Deterministic: says we don't have a choice over being hungry- makes dieting harder. Nature v Nurture: food is based purely on brain messages NATURE (but, nurture= food routines)
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Card 2


What 3 things influence the brain to decide whether we are satiated or hungry?


The stomach, the hypothalamus and hormones.

Card 3


Who did the study which showed the influence of 'stretch receptors'?


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Card 4


What did Cannon & Washburn do?


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Card 5


What did they find?


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