Neural Mechanisms in Eating and Satiation

Homeostasis is a neural mechanism that detects whether or not the body has enough nutrients and if it does not, how to restore the nutrients. Homeostasis works on a negative feedback loop; this is because the time taken to eat a meal is shorter than the time taken to digest even a small amount of food. There are limitations to this explanation. To be adaptive the body must anticipate and prevent hungry instead of just responding to it, this shows that the explanation is not adaptive.

The dual centre theory involves to parts of the hypothalamus, the Lateral and Ventro Medial. The lateral hypothalamus contains the feeding centre and initiates eating behaviour. It responds to a number of things such as the decrease in blood sugar and an increase in the hormone ghrelin, which is a hormone which is produced then the stomach is empty. There are limitations of the LH. One limitation is that damage to the LH has found to cause problems with other bodily functions such as thirst and sex.

This shows that the LH may still play a part in eating behaviour but it may not be the body’s ‘feeding centre’. NPY is an important transmitter that is used to turning on eating. However some research has questioned the important of NPY. Marie et al genetically manipulated mice so that they did not have NPY. She found that this did not cause any change in the rats eating behaviour. This shows that the NPY may not play an important role in turning on eating behaviour.

The Ventro Medial hypothalamus contains the body’s satiety centre, and stops eating behaviour when the body has enough nutrients and the person is full. It responds to increased levels of glucose and decreased levels of ghrelin. The role of the VMH has been criticised. It was first thought that damage to the VMH would cause obesity. However Gold found that damage to the VMH only caused obesity when other parts of the brain were also damaged, such as the PVN. This shows that the VMH may not be the body’s satiety centre.

Research conducted on Mice by Zhang may in the future be very useful for obesity treatment for humans. Zhang found that some mine have two copies of the obesity gene (ob/ob) she also found that these mice did not produce the protein Leptin. Leptin is a protein that is secreted from the body’s fat cell and causes fat loss and a decrease in appetite. She injected the mice with Leptin and found the mice had a dramatic weight loss.

This shows that injection humans with Leptin could be an effect method for helping obese humans to lose weight. Zhang’s research has been criticised. Some people feel that the research that she conducted was unethical and there was use of non-human animal testing, and there is a possibility that the mice may have suffered harm and stress. However some people would argue that the experiments were justifiable due to the benefits that research may have for humans in the future.

This explanation also raises the reductionist debate. This is due to the fact that it simplifies complex human behaviour such as eating and satiation to brain structures and hormones, ignoring factors such as mood and culture. This shows that the biological approach does not give a complex explanation.

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