The autonomic nervous system comprises which two divisions?

• A. Central and Peripheral
• B. Somatic and Autonomic
• C. Endocrine and Nervous
• D. Sympathetic and Parasympathetic

Answer: (D)

The autonomic nervous system is organized into two divisions that regulate involuntary functions by often opposing actions to keep the body in balance. The two divisions are the sympathetic and the parasympathetic systems. They innervate smooth muscle, cardiac muscle, and glands to control things like heart rate, digestion, pupil size, and airway diameter. The sympathetic division tends to prepare the body for activity—think increased heart rate, dilated airways, and blood flow redirected toward muscles. The parasympathetic division promotes rest and recovery—lowering heart rate, constricting pupils, and stimulating digestion. Because they usually act in opposition on the same targets, they provide precise and flexible control of organ function.

The other options don't describe divisions within the autonomic nervous system. Central and Peripheral refer to major parts of the nervous system as a whole, not to subdivisions of the ANS. Somatic and Autonomic describe voluntary versus involuntary control, not the internal branching of the autonomic system. Endocrine and Nervous are two separate systems altogether.