n. any structure or agent that brings about activity in a muscle or gland, such as a motor nerve that causes muscular contraction or glandular secretion. The term is also used for the muscle or gland itself.
adj. 1. designating nerves or neurons that convey impulses from the brain or spinal cord to muscles, glands, and other effectors; i.e. any motor nerve or neuron. 2. designating vessels or ducts that drain fluid (such as lymph) from an organ or part. Compare afferent.... efferent
one of the units (*neurons) that goes to make up the nerve pathway between the brain and an effector organ, such as a skeletal muscle. An upper motor neuron has a cell body in the brain and an axon that extends into the spinal cord, where it ends in synapses. It is thus entirely within the central nervous system. A lower motor neuron, on the other hand, has a cell body in the spinal cord or brainstem and an axon that extends outwards in a cranial or spinal motor nerve to reach an effector.... motor neuron
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