Which of the following is not a branch of the autonomic nervous system?

• A. Somatic
• B. Parasympathetic
• C. Sympathetic
• D. Enteric

Answer: (A)

The autonomic nervous system governs involuntary functions, like heart rate and digestion, and has three main divisions: sympathetic, parasympathetic, and the enteric nervous system. The somatic nervous system, on the other hand, handles voluntary movement of skeletal muscles and conscious sensory input. A key difference is how signals travel: the autonomic system uses two neurons in sequence (a preganglionic neuron from the CNS and a postganglionic neuron outside the CNS in a ganglion) to reach its targets, while the somatic system uses a single motor neuron directly from the CNS to the muscle. Since somatic control is voluntary and lacks the ganglionic two-neuron pathway, it is not a branch of the autonomic nervous system.