Most sought after issues in psychology

If you closely observe the topics predominantly discussed and researched in psychology and the description given above, almost every psychological response seems to have a chemical basis. Neurobiology literature suggests involvement of large number of bodily chemicals in regulating most of the human behaviour. For long the focus within psychobiology was on biogenic behaviour such as eating and sexual behaviour. A large number of bodily chemicals have been found to be involved along with certain regions of the brain. For instance, bodily chemicals implicated for sexual behaviour includes serotonin, dopamine, prolactin, androgens, neuropeptide transmitters of the hypothalamus, intracellular dihydrotestosterone and testosterone receptors. In the due course of time those topics have also been studied which cross-cuts the boundaries of areas within psychology. Dominant and subordinate positions in a social system, leadership, power are few such examples. We shall now look at the details of two widely studied topics in psychology and try to sketch their chemical roots.

Hunger
Earlier studies based on electrolytic lesion suggested that the ventromedial hypothalamic nucleus triggers voracious tendency and such rats have become obese due to this propensity. Lesion of the lateral hypothalamic nucleus encouraged anorexic tendency forcing the animal to starve. When energy storage of the body is depleted, adipose tissuerelease leptin which gives feedback to the central nervous system about this. The pro-opiomelanocortin (POMC) neurons are implicated in the regulation of energy homeostasis in the hypothalamus and leptin influences POMC. The deficiency of POMC increases appetite making us obese.

With the recent trend of studies we know that eating behaviour is influenced by many peptides and hormones. Orexigenic peptides increase whereas anorectic or anorexigenic peptides inhibit eating. Some of the orexigenic peptides are NPY, ghrelin, melanocortin, PYY3-36, and galanin. Anorexigenic peptides include cholecystokinin (CCK), melatonin, neurotensin, and alphamelanocyte-stimulating hormone. Let us take the example of NPY. Neuropeptide Y (NPY) stimulates eating and arcuate nucleus is the site for NYP in the brain. Leptin is a hormone produced by fat cells. It plays a significant role in maintaining normal body weight. Accumulation of fat in the body increases the size of adipose cells. In cases of excessive fat, the adipose cells secrete leptin which, in turn, inhibits NPY in the brain thus reducing eating behaviour. Absence of leptin triggers overfeeding leading to obesity whereas rats without leptin receptor starve. Leptin acts on specific receptors in the arcuate nucleus of the hypothalamus. Cells containing NYP are also found here. Leptin inhibits the release of neuropeptide Y, thus restraining eating behaviour.