The biological foundations of psychology are important because Psychological life depends on biological life for its very existence. This means that the way we behave is influenced greatly by the nature of the body. The aspects of human biology directly relevant to understanding behavior are the brain and nervous system, endocrine glands, and genetic mechanisms. When we do not take into consideration these biological foundations, psychological life could not exist.
A human being’s nervous system can be described both like a powerful computer and a complex communication network. Unlike any computer, the complex mass of nerve cells called the brain not only thinks and calculates but also feels and controls motivation. The brain is connected to the spinal cord, a thick bundle of long nerves running through the spine. Individual nerves exit or enter the spinal cord and brain, linking every part of the body to the brain. Some of these nerves carry messages from the body to the brain to inform the brain about what is going on in the body. Other nerves carry messages from the brain to regulate the body’s functions and the person’s behavior. Without the nervous system, the body would be a mass of uncoordinated parts that could not act, reason, or experience emotions. In other words, without a nervous system, there would be no psychological life.
While the nervous system forms the primary biological basis for behavior and mental processes, the endocrine system of hormone-secreting glands influences emotional arousal, metabolism, sexual functioning, and other body processes. Lastly, some human characteristics and behaviors are influenced by genetic inheritance. Inherited characteristics are passed on through genes, which are segments of DNA on the chromosomes. Research has shown that inheritance plays a significant role in influencing behavior—including intelligence, some aspects of personality, and some aspects of abnormal behavior—but environmental and other personal factors are very important as well. Genetic and environmental factors always operate together to influence psychological characteristics.