Neural and hormonal mechanisms in the control of eating behaviour

What is the hypothalamus?
A small subcortical brain structure made up of two centres: the lateral hypothalamus (LH) and the venture-medial hypothalamus (VMH).
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What does the hypothalamus do?
It regulates homeostasis, part of this is regulating the levels of glucose in the blood.
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How does the Hypothalamus regulate blood glucose levels?
Fluctuations in the levels of glucose in the blood are detected by neurons in the hypothalamus. This then allows it to alter the levels of insulin and anti-insulin.
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What is the role of the LH in eating mechanisms?
The LH contains cells that detect when the levels of glucose in the blood drops. This causes it to activate and make the person hungry and motivates them to eat.
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Which neurotransmitter is associated with the LH and causes hunger?
Neuropeptide Y - causes hunger and reduced physical activity. Rats injected with the neurotransmitter became obese as they ate obsessively.
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What is the role of the VMH in eating mechanisms?
When glucose levels rise the VMH is activated, and LH activity is inhibited. The person is satiated, feels full and stops eating.
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What is the consequence of eating past satiety?
It damages the VMH. Reeves and Plum used the case of a women whose weight doubled in a two years to show this. Her post-mortem revealed she had a tumour on her VMH which caused her the signal to stop eating to fail.
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What is Ghrelin?
A hormone produced by the cells in the stomach wall which act as an appetite stimulant, contributing to the signal to start eating.
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What is the role of Ghrelin in eating mechanisms?
Ghrelin is secreted in the stomach and the amount produced is linked to how full our stomach is. Ghrelin is detected by part of the hypothalamus, when it rises above a certain point a signal is sent to produce neuropeptide Y.
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What study supports the role of Ghrelin?
Wren et al - found that when people were given Ghrelin their food intake increased. They found that the amount of Ghrelin in the bloodstream doubled just before a meal and decreases rapidly after one. This was correlated to their level of hunger.
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What is leptin?
A hormone produced by fat cells which acts as an appetite suppressant.
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What is the role of leptin in eating mechanisms?
Leptin is produced by fat cells, when the level in the blood increases it is detected by the VMH. This contributes to the VMH's satiety mechanism, the individual feels full and stops eating.
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What study supports the role of leptin?
Licinio et al - studied a rare genetic disorder which makes people unable to produce leptin. It is associated with severe obesity. The treatment is leptin replacement therapy. They found this led to a 40% weight loss and 49% decrease in food intake.
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Card 2

Front

What does the hypothalamus do?

Back

It regulates homeostasis, part of this is regulating the levels of glucose in the blood.

Card 3

Front

How does the Hypothalamus regulate blood glucose levels?

Back

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Card 4

Front

What is the role of the LH in eating mechanisms?

Back

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Card 5

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Which neurotransmitter is associated with the LH and causes hunger?

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