Nerve Structure (Anatomy)
Organization of the Autonomic System
- Nerves also contain neurons of the visceral or autonomic nervous system (ANS), which connect the central nervous system (CNS) to the viscera.
- The viscera are the soft organs found in the respiratory, circulatory, endocrine, digestive, urinary, and reproductive systems. Examples of viscera include the heart, glands, and smooth muscles.
- The autonomic neural network allows the brain to involuntarily (subconsciously or unconsciously) monitor changes in the internal environment and control the activities of the viscera.
- Activity of the ANS is regulated by brain control centers in the hypothalamus and brainstem.
- Input is sent to the ANS control centers from higher levels of the brain (cerebral cortex and limbic system) and sensory receptors embedded in the viscera. Autonomic sensory neurons conduct signals from the visceral receptors to the CNS.
- Using the sensory input, the ANS control centers develop appropriate responses (reflexes), which are then relayed to autonomic motor neurons.
- Autonomic motor neurons carry signals out of the CNS to the heat, glands and smooth muscle. Each pathway to an effector location consists of two neurons.
- Functionally and anatomy, the motor divided into the sympathetic and parasympathetic nervous systems.
- The sympathetic N.S. promotes activities that help the body cope with stress (fight or flight responses).
- In contrast, the parasympathetic N.S. promotes activities that support the body while at rest (feed and breed).