Neural Mechanisms in Eating and Satiation

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Neural mechanisms in eating and satiation Homeostasis is how the body maintains a constant internal environment. The homeostasis involves mechanisms that detect the state of the internal environment and also correct it to restore that environment to its optimal state. There are set points in the brain and any deviation in the body will trigger mechanisms in the brain (e.g. lack of food will initiate the feeling of hunger). The set points are adaptive from our evolutionary past; the weight of our body is regulated around these points. The hypothalamus is in the brain and controls the feelings of hunger and satiation. There are two systems involved in homeostasis, one for turning on eating and one for turning it off. A decline in glucose levels in the blood activates the lateral hypothalamus (LH) resulting in feelings of hunger, so causes eating which increases glucose levels. A rise in glucose levels activates the ventromedial hypothalamus (VMH) leading to feelings of satiation which inhibit further eating. Research has found that damage to the lateral hypothalamus (LH) in rats results in aphagia (decreased feeding). The stimulation of the LH stimulates eating, it is therefore suggested that the LH is the 'on' switch for feeding. Researchers also found that stimulation of the LH elicits feeding behaviour .Damage to the VMH causes hyperphagia (overeating) in rats. Stimulation of this area inhibits feeding. Hence, the VMH thought of as the ‘off switch’ for eating behaviour. It has been concluded that the VMH is the 'satiety centre' and stops feeding. Damage to nerve fibers passing the VMH also damages other parts of the hypothalamus. T EVALUATION Cummings et al (2004) monitored PPs’ ghrelin levels every 5 minutes. PPs had to assess their level of hunger every 30 minutes. In 5 of the 6 participants there was a significant correlation between ghrelin levels,

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