Motor neuron

Definition
noun, plural: motor neurons
A type of neuron connected to a muscle fiber and originates from the central nervous system
Supplement
The motor neuron is a type of neuron in which the cell body is in the spinal cord of the central nervous system. Its axon projects from the spinal cord and connected to a muscle fiber. The motor neuron is an efferent neuron since it transmits impulses away from the central nervous system towards the periphery.
The motor neurons may be divided into upper motor neurons and lower motor neurons. The upper motor neurons are those that originate from the motor region of the cerebral cortex or from the brain stem. The lower motor neurons are those found in the anterior grey column, anterior nerve roots, cranial nerve nuclei of the brainstem, and cranial nerves (i.e. with motor function).¹ The upper motor neurons relay the motor information down to the lower motor neurons through synapses. The lower motor neurons are further classified as: (1) alpha motor neurons, (2) beta motor neurons, and (3) gamma motor neurons. The lower motor neurons effect muscle movement when neurotransmitters are released at the neuromuscular junction and activate muscle fibers.
Variant(s):

• motor neurone

Synonym(s):

See also:

• efferent neuron
• effector

Reference(s):

¹ Fletcher, T.F. “Clinical Neuroanatomy Guide”. Retrieved from ://vanat.cvm.umn.edu/mLocLesGui/clinAnat.html.