Glossary
somatic nervous system
The somatic nervous system is the motor division that carries commands to skeletal muscle, the muscle a person moves on purpose.
The somatic nervous system is the part of the motor (efferent) pathway that carries commands to skeletal muscle, the muscle a person moves on purpose. The motor half of the peripheral nervous system divides in two: the somatic division reaches skeletal muscle, and the autonomic division reaches the smooth muscle of organs and vessels, the heart and the glands, without conscious control. The autonomic side divides again into sympathetic and parasympathetic branches, which push the same organs in opposite directions. A somatic reflex runs on a loop — receptor, sensory neuron, an integration point in the spinal cord, motor neuron, muscle — and the knee-jerk reflex is the clean example, because it never needs the brain to complete. The word itself is the mnemonic: soma is body, and the somatic division is the one that moves the body's frame.
Taught in
Related terms
- reflex arc — A reflex arc is the pathway a reflex travels — receptor, sensory neuron, a synapse in the CNS, motor neuron and effector — without waiting for the brain.
Source: The anatomy and physiology guide in this course, whose organ and tissue descriptions follow the US National Cancer Institute's SEER Training Modules and MedlinePlus consumer health pages. Both are US federal government material, not subject to copyright in the United States. The definition above is written for this course in our own words. (SEER Training Modules accessed 2026-10-26; definition written 2026-10-27)