Psychology is both a social and a biological science. The relevance of the biological approach for many fields of psychology is demonstrated by the fact that biological bases of behavior are mentioned in most of the following chapters. The field that studies biological aspects of psychology and biological contributions to psychology has been given several names. Originally it was called physiological psychology' when physiology' was used to designate what we now call biomedical sciences. As specialized fields broke off from physiology including biochemistry, immunology, and neurochemistry genetics and endocrinology the designation physiology' became too narrow, so the more inclusive term biological psychology' became more appropriate. Other terms sometimes used for this field include physiology and behavior' and behavioral neuroscience'. The development of neuroscience as an integrated but multidisciplinary field in the last quarter of the twentieth century benefited biological psychology (behavioral neuroscience). Through the progress of neuroscience, biological psychology strengthened its ties and interactions with neighboring sciences and advanced its program of research and applications. Biological psychology is concerned with both similarities and differences among individuals.
[...] For studying and understanding many kinds of behavior, biological and social perspectives offer complementary avenues. In other cases, biological and social factors continuously interact and affect each other. We will give examples of both kinds. A major field of biological psychology is investigating the biological mechanisms of learning and memory storage how these processes occur, where in the nervous system they occur, how and why different kinds of learning vary over the life span. Biological research complements social and cognitive research on learning and memory. [...]
[...] Activity of the endocrine system is under hierarchical control, which provides one example of interactions between the endocrine and the neural systems. Neurons in certain nuclei of the hypothalamus secrete various releasing hormones into the median eminence, whence they are sent by the portal vein system to stimulate the anterior lobe of the pituitary gland to secrete different tropic hormones. These in turn regulate the activity of the adrenal glands, the gonads and the thyroid gland. Steroid hormones secreted by the peripheral endocrine glands or the pituitary enter the CNS and bind to receptors in the hypothalamus or elsewhere in the brain to exert an inhibitory feedback control on the secretion of various releasing or tropic hormones. [...]
[...] Thus, at any moment the level of testosterone is determined, in part, by recent dominance-submissive social experience, and the level of testosterone determines, in part, the degree of dominance and aggression. Of course, social/cultural factors also help to determine the frequency of aggression; cross-cultural differences in rates of aggression exist that cannot be correlated with hormonal levels, and ways of expressing aggression and dominance are determined in part by sociocultural factors. The neurotransmitter serotonin is another of several biological factors correlated with the magnitude of aggression, but in this case the correlation is negative; that is, the greater the aggression, the lower the concentration of serotonin. [...]
[...] The Immune System More and more evidence indicates intimate interactions between mental activity and the immune system. This system defends an organism from harmful foreign biological substances introduced into the body. So-called natural killer cells, members of the immune system, roam around the body to destroy infected cells or cancer cells. In addition, cells infected by viruses may secrete a peptide named interferon to suppress further reproduction of the virus. These are nonspecific actions of the immune system. Immune responses may also attack specific targets. [...]
[...] Those nerves carrying information from and to the viscera and involved in control of their activity form the autonomic nervous system (ANS) which is further divided into the sympathetic and parasympathetic branches. The spinal cord processes information from sensory receptors, delivers motor orders to the muscles, and serves as a relay between the brain and the periphery. The brain contains a central core known as the brain stem including the medulla, pons, midbrain, thalamus, and hypothalamus. Around the brain stem are the basal ganglia and limbic system. [...]
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