Afferent pathways

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The mechanism of the reflex arc

In the nervous system, Afferent pathways are made of bundles of afferent neurons --otherwise known as sensory or receptor neurons-- which 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. Afferent neurons are pseudounipolar neurons, that have a single long dendrite and a short axon, and a smooth and rounded cell body. The dendrite is structurally and functionally similar to an axon, and is myelinated; it is these axon-like dendrites that make up the afferent nerves. 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.)

Etymology and mnemonics

Both afferent and efferent come from french, as evolution from latin (much used in medicine) of respectively ad ferentes (latin verb fero : I carry), meaning carrying into, and ex ferentes, meaning carrying away. Ad and ex give an easy mnemonic device for remembering the relationship between afferent and efferent : afferent connection arrives and an efferent connection exits.

See also

• Leminiscal system
• Spinalthalamic tracts
• Dorsal horns
• Efferent pathways
• Receptor fields

External links

• Dorlands/Elsevier n_07/12569826