Amyotrophic lateral sclerosis (ALS) is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, and causes loss of muscle control, and impacts physical functions.
ALS is a disease that affects motor neurons. These nerve cells send messages from the brain to the spinal cord and then to the muscles. There are two main types of motor neurons:
- Upper motor neuron (nerve cells in the brain)
- Lower motor neuron (nerve cells in the spinal cord to muscles)