Wednesday, November 6, 2019
The role of neural mechanisms in the role of hunger and satiety Essays
The role of neural mechanisms in the role of hunger and satiety Essays The role of neural mechanisms in the role of hunger and satiety Neural structures plays a key role in eating behaviour. Among humans, glucose levels probably play the most important role in producing feelings of hunger. Hunger increases as glucose levels decrease. A decline in glucose levels in the blood and an increase in ghrelin (a hormone released by the stomach when it is empty) activates a part of the brain called the lateral hypothalamus, resulting in feelings of hunger. The lateral hypothalamus (or LH), is also known as the start eating switch. This causes the individual to search for and consume food. The ventro-medial hypothalamus (or VMH), is also very important also known as the stop switch. A rise in glucose levels and a decrease in ghrelin (hormone that is released from the stomach when there is no food in it) activates the ventromedial hypothalamus, which leads to feelings of satiation, which in turn inhibits further feeding. There has been considerable research evidence to indicate support for the role that neural mechanisms play in hunger and satiety. The role that the hypothalamus plays has been supported by studies looking at lessoning regions of this structure. Research has illustrated the crucial roles played by the hypothalamus Hetherington and Rammington (1942) published a famous study on the control of eating behaviour. They showed that lesioning (i.e. destroying) tiny areas in the LH in rats, led to a loss of interest in food and eating, the animals seemingly unaware that they were starving themselves. Whereas the opposite happened with lesions to the VMH as this led to the rats eating so much they became obese. The importance of the role of the hypothalamus has been replicated in further studies where the role of neurochemicals (neuropeptide Y) has also been supported. Lutter (2008) has found supporting evidence for the role of ghrelin as being crucial in boosting appetite. He concluded that ex tra levels of ghrelin were produced in stressed individuals which caused them to overeat. However, it may be possible that other psychological processes were overlooked in this study (e.g. psychological impact of mood) A great deal of the research done on neural mechanisms has been done using rats which means that it is difficult to generalize. Rats do not have a functioning prefrontal cortex like humans do, and this is what helps humans make judgements so how far can we say the studies using animals supports the role of neural mechanisms in humans. However, Research studies have looked at fMRI of cases of individuals with Prader-willi (who have a compulsion to eat) syndrome in comparison to controls (when eating) and have found a deactivation in the hypothalamus of PWS patients. This is a good study as it has been done on humans and uses scientific objective measures (FMRI scans) which means that it is a valid study that shows the importance of the role of the hypothalamus in humans. Moreover another factor is hormones such as insulin and leptin are also involved in eating behavior. Low levels of leptin will increase hunger and eating behavior, as it does not stop neuropeptide Y (a neurochemical that stimulates hunger). Elevated levels of leptin, stops neuropeptide and decreases eating behaviour. The neural mechanisms explanations (biological approach) can be seen as an example of Biological determinism: it focuses exclusively on the role of nature and no space left to choice and cultural and social influences. There is substantial and convincing evidence that social, cultural and psychological factors affect our eating behaviours as is evident from psychological explanations of eating disorders. For example research into mood has shown that when we are in a bad mood we are more likely to crave carbohydrates. This suggests that there are other reasons that govern what we eat and that is not just down to neural control. To take the biological explanations only would be a reductionist account, though when coupled with the psychological explanation it covers both the nature and nurture side in the nature/nurture debate, thus being a more complete explanation of eating behaviours.