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Motor neuron
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Raising an arm, taking a step, drawing a breath, saying a word or swallowing a bite of food are different actions with one thing in common: motor neurons, the nerve cells that control skeletal muscle, the muscle that carries out all of those movements.
The command does not reach the muscle in a single leap; it usually travels in two stages, like the baton in a relay race. It first sets off from nerve cells in the brain, which is why they are called upper motor neurons. They hand the signal off to other cells that sit in the brainstem and the spinal cord, the lower motor neurons, and these are the ones that carry the signal out to the muscles throughout the body. That is how we move. And that is why the final leg matters: when the signals from the lower motor neurons to the muscle are interrupted, the muscle weakens and gradually shrinks in size, like a tool that goes unused.
In brief
Motor neurons are the cells that control skeletal muscle activity, such as walking, breathing, speaking and swallowing.
Signals from nerve cells in the brain, the upper motor neurons, typically pass to cells in the brainstem and spinal cord, the lower motor neurons, and from there to the muscles.
The order travels like a relay baton: from the brain to the spinal cord, and from there to the muscle.
If the signals from the lower motor neurons to the muscle are interrupted, the muscle begins to weaken and shrink in size.
Sources (1)
- National Institute of Neurological Disorders and StrokeMotor Neuron Diseases
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated