Reference no: EM133930908

Question

The peripheral (outside of the CNS) processes of the somatic nervous system form the somatic peripheral nerves, which are structurally and functionally different from the autonomic nervous system. The somatic peripheral nervous system is a single neuron system with the motor neurons lying inside the brainstem or spinal cord and the sensory neurons lying in the dorsal root ganglia. The autonomic peripheral nervous system is a two neuron system with a neuron lying outside of the CNS in the autonomic ganglia. The nerve fibers have different sizes with different conduction velocities. The size depends on the actual size of the axons and, more importantly, the degree of myelination, which provides electrical insulation and fast conduction seed through the so-called "saltatory conduction." The fastest conducting fibers are, therefore, the most heavily myelinated. They are the motor fibers from the motor neurons and sensory fibers serving discriminative touch, joint position, and vibratory sensations. The small fibers are mainly sensory fibers serving pain and temperature sensations.