es and glands. Lastly, interneurons occur in the brain, eyes, and spinal cord. These specific nerve cells receive signals from sensory neurons, and transmit them to either other interneurons or to motor neurons (Psychology text, p. 37).
Although all of its parts are interrelated, the human nervous system may be subdivided into various distinct components. Its two major subdivisions include the central and peripheral nervous systems. The central nervous system (CNS) consists of the brain and spinal cord; the peripheral nervous system is comprised of two further subdivisions, the somatic and autonomic systems. The sensory and motor nerves of the somatic nervous system serve as a link between the CNS and the skin, muscles, and joints. In contrast, the autonomic nervous system regulates the internal organs. It is responsible for the control of such processes as respiration, heart rate, and digestion.
As with the nervous system in general, the human brain can likewise be subdivided into various parts. These different structures may be considered to function similarly to a "network of interrelated computers (Psychology text, p. 48)." Although each individual structure has a specialized job to do, all of the brain's components work together.
For the most part, the human brain may be divided into three concentric layers. These consist of the central core, the limbic system, and the cerebrum (i.e., the cerebral hemispheres). The central core--which includes most of the brainstem--also contains the medulla. This enlarged portion of the brainstem controls breathing and reflexes, and is also the crossing point for the spinal cord's major nerve tracts. Thus, nerves originating in left side of the brain end up connected to the right side of the body, and vice versa (Psychology text, p. 44).
In humans, the cerebrum is more highly developed than in any other organism. Its gray outer layer, known as the cerebral cortex, co...