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Functional Classification

Sensory neurons transduce physical stimuli, such as smell, light, or sound, into action potentials, which are then transmitted to the spinal cord or brain. Sensory neurons, which bring information into the central nervous system, are also referred to as afferent neurons. Motor neurons transmit nerve impulses away from the brain and spinal cord to muscles or glands and are also called efferent neurons. Interneurons transmit nerve impulses between sensory neurons and the motor neurons. Interneurons are responsible for receiving, relaying, integrating, and sending nerve impulses. Interneurons are found exclusively in the central nervous system and account for almost 99% of all the nerve cells in the body.



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Thibodeau, Gary A., and Kevin T. Patton. Anatomy & Physiology. 5th ed. St. Louis: Mosby, 2002.

K. Lee Lerner
Christine Miner Minderovic


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Action potential

—A transient change in the electrical potential across a membrane which results in the generation of a nerve impulse.

Afferent neuron

—A sensory neuron that carries an impulse toward the central nervous system.


—The threadlike projection of a neuron that carries an impulse away from the cell body of the neuron.


—A mental state involving awareness of the self and the environment.


—Branched structures of nerve cell bodies which receive impulses from axons and carry them to the nerve cell body.

Efferent neuron

—A motor neuron that carries an impulse from the central nervous system to muscles or glands.


—The ability to recall thoughts or events.

Myelin sheath

—A white phospholipid (fat) covering of peripheral nerve axons.


—Specialized nerve cells also called glial cells. The Schwann cell is a glial cell.


—Protective nerve covering made by Schwann cells.

Additional topics

Science EncyclopediaScience & Philosophy: Mysticism to Nicotinamide adenine dinucleotideNeuron - Structure And Function, Structural Classification, Glial Cells, Functional Classification