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Skip Navigation LinksPennsylvania Department of Health > My Health > A-Z Health Topics > A-D > Amyotrophic Lateral Sclerosis (ALS)
Amyotrophic lateral sclerosis 

What is ALS?

Amyotrophic lateral sclerosis  or ALS is often referred to as "Lou Gehrig's disease."  ALS is a nervous system disease that affects the voluntary muscles in your body.


There a 3 types of muscles in your body

  • Voluntary muscles of the skeletal system
    • Helps you control muscles in upper and lower body to do such things as walk, use your hands to write and use your arms to lift things
  • Involuntary smooth muscles
    • Handle body functions you don�t think about such as pushing food along in the digestive system and focusing your eyes
  • Involuntary cardiac muscles
    • Helps your heart beat and pump blood through your heart


How Does ALS Affect Your Voluntary Muscles?


  • Everyday your brain uses nerve cells or neurons to help you send messages to control the voluntary muscles in your upper and lower body
    • First messages are sent to your spinal column
    • Messages then travel to your voluntary muscles to help you control what you want them to do
  • When you have ALS
    • Nerve cells in your brain and spinal cord are attacked
    • Nerve cells weaken and die when attacked
    • No longer able to send the messages that cause the muscles to work
    • Muscles will become weak, waste away, and twitch
    • Eventually the brain and spinal cord lose the ability to start and control voluntary movement of these muscles


ALS is the most common neuromuscular disease in the world.

Each year an estimated 5,000 new people in the United States are diagnosed with ALS.   As many as 20,000 Americans are currently living with ALS. (NIH)  




What Types of Nerves Make Your Body Work Properly? 

ALS Nerve Cells    

The body has many kinds of nerves. There are those involved in the process of thinking, memory, and of detecting sensations (such as hot/cold, sharp/dull), and others for vision, hearing, and other bodily functions. The nerves that are affected when you have ALS are the motor neurons that provide voluntary movements and muscle power. Examples of voluntary movements are your making the effort to reach for the phone or step off a curb; these actions are controlled by the muscles in the arms and legs.


The heart and the digestive system are also made of muscle but a different kind, and their movements are not under voluntary control. When your heart beats or a meal is digested, it all happens automatically. Therefore, the heart and digestive system are not involved in ALS. Breathing also may seem to be involuntary. Remember, though, while you cannot stop your heart, you can hold your breath - so be aware that ALS may eventually have an impact on breathing.

(Source: The ALS Association's Living with ALS, Manual 1: What's It All About?)