Physiology of the autonomic nervous system

Abstract

The autonomic nervous system is not under voluntary control. Its major role is to ensure homeostasis, that is, a stable internal environment. The body’s internal environment is monitored by sensory receptors (section 1.5.3) which transmit neural impulses along afferent nerves to the central nervous system. The central nervous system in turn relays the appropriate responses to the incoming sensory information via efferent autonomic nerves. Thus, when the body’s internal environment is challenged, the autonomic nervous system responds through its connections with the tissues. In addition, neural activity in the higher centres (such as conscious thought arising in the cerebral cortex or emotions arising in the limbic system) influences brainstem nuclei which form neural connections with sympathetic autonomic neurones. This anticipatory increase in autonomic nervous activity is an important response prior to exercise. In preparing the body for exercise the effects of the sympathetic autonomic nerves help to reduce the challenge that exercise itself presents.