The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and the spinal cord, while the PNS consists of all the nerves that connect the CNS to the rest of the body.

Somatic motor neurons are neurons that carry signals from the CNS to skeletal muscles. These neurons are located in the ventral horns of the spinal cord and the motor nuclei of the brainstem. When a somatic motor neuron is activated, it sends a signal to a skeletal muscle, causing the muscle to contract.

There are two types of somatic motor neurons: alpha motor neurons and gamma motor neurons. Alpha motor neurons innervate extrafusal muscle fibers, which are the fibers that generate force during muscle contraction. Gamma motor neurons innervate intrafusal muscle fibers, which are specialized muscle fibers that help to control the sensitivity of the muscle spindle.