A motor neuron is one of the nerve cells (neurons) that goes
to make up the nerve pathway (motor nerves)
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. See also sensory nerve.
|Photomicrograph of the body of a motor neuron. The
cell nucleus and the sensory dendrites are clearly visible. The motor
axon leaves at the bottom of the picture