In the nervous system, afferent neurons--otherwise known as sensory or receptor neurons--carry nerve impulses from receptors or sense organs toward the central nervous system. This term can also be used to describe relative connections between structures. Afferent neurons communicate with specialized interneurons. The opposite activity of direction or flow is efferent.

In the nervous system there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of afferent neurons, interneurons, and efferent neurons.

A touch or painful stimulus, for example, creates a sensation in the brain only after information about the stimulus travels there via afferent nerve pathways. The structure of an afferent neuron contains a single long dendrite and a short axon; the shape of the cell body of an afferent neuron is smooth and rounded. Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the dorsal root ganglion. (See efferent nerve)

An easy mnemonic device for remembering the relationship between afferent and efferent is that an afferent connection arrives and an efferent connection exits.