Is als a disease of the muscles or nerves?

The nerves: Als or amyotrophic lateral sclerosis ( or "lou gehrig's disease") is a disease in which the motor nerves in the brain, or in the spinal cord degenerate and die, leaving the muscles weakened. This is progressive and results in paralysis and even death over time. The rate of progression varies with the kind of ALS and the patient. Although the disease is not curable patients benefit from support.

Nerves: Als is a disease of the nerves, affecting the central nervous system and lower motor neurons. Since nerves ultimately supply muscles, you see the muscles being affected, but that pathology lies in the nervous system.

Anterior horn cells: Als is a disease that affects nerve cells in the anterior horn (front) of the spinal cord. This is the location of nerve cells that form the 'lower circuit' to the muscles of the face, neck, spine, arms, and legs. It results in a mix of symptoms including weakness and paralysis, spasticity and muscle spasms, hyperactive reflexes, as well as muscle twitching (fasciculations), and atrophy.

Nerve: Specifically, affects the motor nerve cell in brain and spinal cord.