Functional Classification of Nerves

Nerves convey electrical information into and out of the CNS. Sensory information is conducted into the CNS from a sensory receptor. Motor information is conducted out of the CNS to an effector, a cell or organ that can respond to a command. Individual axons contained within a nerve can only transmit information in one direction, that is, each axon functions as either a sensory or motor fiber.

Since a nerve is a collection of axons, nerves can be categorized by the direction of information flow present within the contained axons. This functional classification gives rise to three types of nerves:

1. Sensory nerves: Sensory nerves only carry sensation into the CNS and are associated with special senses.

2. Motor nerves: Motor nerves primarily convey commands from the CNS to effectors like skeletal muscle, the heart, and glands.

3. Mixed nerves: Most nerves contain both sensory and motor axons and are known as mixed nerves. Mixed nerves' sensory and motor functions are typically unrelated, for example, facial sensation and control of chewing muscles.