What does ALS do to the nervous system?
We can divide the muscle-controlling nerve cells, or motor neurons, into two types. The upper motor neurons are located in the upper part of the brain and exert some control over the lower motor neurons in the brainstem and the spinal cord. The lower motor neurons are attached to muscles through wires called axons. Bundles of these axons leave the spinal cord and extend out to the muscles all over the body. (These are the bundles that doctors are referring to when they talk about the nerves.) The function of lower motor neurons is straightforward; they send “go” signals to muscles. When these cells gradually die, as is the case with ALS, muscles become progressively weaker and eventually unable to move. This causes paralysis in patients. The lower motor neurons that control most of the body are in the spinal cord, and those that control the muscles of speaking, swallowing, and facial expression are in the brainstem. Another name for these is bulbar motor neurons, because the part of th
