Lower motor neuron

A neuron whose axon directly activates skeletal muscle, with its cell body in a brainstem motor nucleus or the spinal cord. It forms the final neural link to voluntary muscle contraction.

Neuromuscular junction: The synapse where a motor neuron communicates with a skeletal muscle fiber. This is the contact point where a lower motor neuron's signal reaches muscle.
Anterior horn: The ventral region of spinal gray matter containing many motor neuron cell bodies. Spinal lower motor neuron cell bodies are located here.
Upper motor neuron: A neuron in the brain or spinal cord that influences movement through connections to lower motor neurons. Unlike lower motor neurons, upper motor neurons do not directly innervate skeletal muscle.
Lower motor neuron lesion: Damage to motor neurons or their axons that directly innervate skeletal muscle. It describes the clinical consequence of injury to this neural output pathway.
Corticospinal tract: A descending pathway from the cerebral cortex to spinal and brainstem motor circuits. It influences lower motor neurons, especially those controlling skilled limb movements.
Acetylcholine: A neurotransmitter that activates receptors at skeletal neuromuscular junctions. Lower motor neurons release it to trigger muscle-fiber excitation.
Cranial nerve motor nucleus: A brainstem group of neurons whose axons contribute to a cranial nerve's motor component. Many lower motor neurons controlling the head and neck lie in these nuclei.
Interneuron: A neuron that connects to other neurons rather than directly innervating an effector. Interneurons shape motor commands but are not the final neural link to muscle.
Flaccid paralysis: Weakness or paralysis accompanied by reduced muscle tone. Loss of lower motor neuron output can leave affected muscles flaccid.
Stretch reflex: A reflex contraction caused by stretching a muscle and activating its sensory receptors. Its spinal circuit excites lower motor neurons to resist sudden muscle stretch.

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