A reference to the bodily sensations of fast localized pain, slow, poorly localized pain, and temperature.

Protopathic sensibility is transmitted principally along the thinnest nerve fibers, which lack a myelin sheath and conduct nerve impulses slowly.

It is related primarily to the spinothalamic system (extending between the spinal cord and the thalamus which is the large oval area of gray matter within the brain that relays nerve impulses from the basal ganglia to the cerebellum, both parts of the brain that control and regulate muscle movement), whose receptive neuron fields are often nonspecific and very large, covering the entire body.