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A dorsal root is the bundle of sensory axons entering the posterior side of the spinal cord at a spinal level. The associated dorsal root ganglion contains the soma of many of these sensory neurons. Their peripheral processes receive information from the body, while their central processes enter through the dorsal root.^[ref]

The dorsal root joins the ventral root to form a mixed spinal nerve. This organization separates sensory entry from motor exit close to the spinal cord while allowing both directions to share a peripheral route. The dorsal root ganglion houses cell bodies; it is not normally a chain of sensory-to-sensory synapses.

A dorsal root ganglion is a collection of sensory neuron cell bodies on a dorsal root associated with a spinal nerve. These neurons carry information from peripheral tissues toward the spinal cord, including signals relevant to touch, temperature, pain and proprioception.

The sensory axon typically branches into a peripheral process and a central process; the ganglion is not simply a relay in which every incoming signal must cross a synapse onto another neuron. Its neurons also comprise multiple functional populations. Single-cell RNA sequencing of mouse dorsal root ganglion neurons separated molecularly distinct sensory types without assigning them beforehand solely from a few selected markers.^[ref] Anatomical location, molecular profile and stimulus response provide complementary descriptions of a sensory neuron.

A pseudounipolar neuron has one main process leaving its soma and dividing into peripheral and central branches. Many primary sensory neurons in dorsal root ganglia have this shape. The peripheral branch receives sensory input and the central branch conducts toward the spinal cord; the soma lies to the side of this principal conducting route.^[ref]

This arrangement explains why the familiar drawing of input entering the soma before reaching an axon is not a universal circuit diagram for a neuron.

A sensory neuron carries information about a stimulus toward the central nervous system. Its input can concern the external world or the body's own state. For example, stretching a muscle spindle changes the activity of a sensory neuron; the resulting action potentials help the spinal cord regulate muscle activity through a reflex.^[ref]

Many sensory neurons supplying the body have their soma in a dorsal root ganglion and a branching axon with peripheral and central processes. Thus the soma is not simply an obligatory relay between an input dendrite and an output axon. Other sensory pathways use different arrangements; a sensory function does not specify one universal neuron shape.^[ref]