Autonomic Nervous System

AUTONOMIC NERVOUS SYSTEM The autonomic nervous system (ANS) is the portion of the PNS that functions independently, automatically, and continuously, without conscious effort. It helps to regulate the smooth muscles, cardiac muscle, digestive tube, blood vessels, sweat and digestive glands, and certain endocrine glands. The autonomic nervous system is not directly under the control of the brain but usually works in harmony with the nerves that are under the brain's control. The autonomic nervous system includes two subdivisions (the sympathetic and parasympathetic nervous systems) that act together. The sympathetic nervous system's primary concern is to prepare the body for energy-expending, stressful, or emergency situations. On the other hand, the parasympathetic nervous system is most active under routine, restful situations. The parasympathetic system also counterbalances the effects of the sympathetic system, and restores the body to a resting 1-40 HM3F0146 C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9 L1 L2 L3 L4 L5 S1 S2 S3 S4 S5 Co T10 T11 T12 POSTERIOR VIEW CERVICAL NERVES THORACIC NERVES LUMBAR NERVES SACRAL NERVES COCCYGEAL NERVE Figure 1-46.—Spinal nerves.