Which statement describes a typical characteristic of the somatic nervous system?

Which statement describes a typical characteristic of the somatic nervous system?

• A. A single neuron from the CNS to skeletal muscle.
• B. A two-neuron autonomic chain.
• C. Three neurons including a dorsal root ganglion.
• D. Neurons located entirely within the brain.

Answer: (A)

At its simplest, the somatic nervous system controls skeletal muscles with a single motor neuron that leaves the central nervous system and directly innervates the muscle fiber at the neuromuscular junction. This one-neuron pathway, with cell bodies in the ventral horn of the spinal cord or brainstem and axons that project straight to the muscle, underlies rapid, precise voluntary movement. This contrasts with autonomic circuits, which use a two-neuron chain (a preganglionic neuron in the CNS and a postganglionic neuron in a peripheral ganglion) before reaching the target. The dorsal root ganglion contains sensory neuron cell bodies, not motor outputs, so it’s not part of the classic somatic motor pathway. And while motor commands originate in higher brain regions, the final efferent neurons that reach skeletal muscle are located in the spinal cord or brainstem and extend to the periphery, not entirely within the brain.

At its simplest, the somatic nervous system controls skeletal muscles with a single motor neuron that leaves the central nervous system and directly innervates the muscle fiber at the neuromuscular junction. This one-neuron pathway, with cell bodies in the ventral horn of the spinal cord or brainstem and axons that project straight to the muscle, underlies rapid, precise voluntary movement.

This contrasts with autonomic circuits, which use a two-neuron chain (a preganglionic neuron in the CNS and a postganglionic neuron in a peripheral ganglion) before reaching the target. The dorsal root ganglion contains sensory neuron cell bodies, not motor outputs, so it’s not part of the classic somatic motor pathway. And while motor commands originate in higher brain regions, the final efferent neurons that reach skeletal muscle are located in the spinal cord or brainstem and extend to the periphery, not entirely within the brain.