Last updated: Tue, Nov 19, 2024
Each of the spinal nerves is enclosed in a membrane that separates it from the surrounding tissue. The nerves branch repeatedly until individual neurons emerge. Each spinal nerve contains three functional types of axons: 1) motor axons that cause muscles to contract; 2) sensory axons; and 3) sympathetic axons that control functions such as the size of arteries and sweating. See Figure 1: A spinal nerve1 for the structure of a large nerve.
Each sensory axon travels the entire distance from the spinal cord to the neuron's sensory receptors. The tiny axon of each of the tens of thousands of nerves that go to the foot can be almost a meter long.
The cell bodies of all of the sensory neurons in a spinal nerve are contained in a single node, nestled between the vertebrae where the nerve emerges from the spinal cord, called the dorsal root ganglion.