motor neuron(e) (motoneuron(e))

Alpha motor neuron from anterior horn cell to nerve terminals.

motor neuron(e) (motoneuron(e))

a nerve cell and its axon which is part of a pathway for activation of muscle. An upper motor neuron has a cell body in the brain and its axon runs to a synapse with another at a relay station, or directly with a lower motor neuron, the final link to muscle. The cell bodies of the lower motor neurons are in the anterior horns of grey matter in the spinal cord or in nuclei of cranial nerves. alpha motor neurons serve the main (extrafusal) skeletal muscle fibres; gamma motor neurons serve the (intrafusal) fibres of muscle spindles. See also gamma (motor) system, motor unit; appendix 1.1 .