Listed below are the organs/organ systems affected by ALS and they way in which they are affected:
Organs:
- Brain - The upper motor neurons present in the brain degenerate due to ALS. The lower motor neurons present in the brainstem also degenerate.
- Spine - The lower motor neurons in the spine degenerate due to ALS.
- Tongue - The tongue may experience chronic denervation in which the communication between nerves and the tongue has been disrupted or cut off. This is caused by the motor neurons in the brain and spine degenerating. Eventually this can lead to the tongue becoming fatty causing difficulty in eating food.
A magnetic resonance imaging (MRI) scan of an ALS patient with a fatty tongue, shown on the left, compared to the normal, muscular tongue, shown on the right.
Organ Systems:
- Nervous System
- Central Nervous System (CNS) - This system is directly affected since upper and lower motor neurons in the brain and the spine degenerate during ALS.
- Peripheral Nervous System (PNS) - This system is generally not directly affected but since the central nervous system is not functioning correctly, the messages carried by the peripheral nervous system (from the CNS) may be incorrect. In some cases, the CNS may not send out a message which it should have causing the muscles to function incorrectly since they never received the message through the PNS.
- Musculoskeletal System - Since motor neurons are no longer able to control muscle movement, the musculoskeletal system is not able to control voluntary muscles which are controlled by the motor neurons.
- Digestive System - Since the tongue can be affected by ALS, the entire digestive system can have difficulty digesting food. The tongue is essential in the mechanical breakdown of food (mastication/chewing) which means if it is fatty and cannot communicate with the brain then it is very difficult to swallow and digest food.
- Respiratory System - In the later stages of ALS, the muscles moving air in and out of the lungs may be weakened to the point at which they cannot function properly. This can cause a person to have difficulty breathing or even lead to suffocation.
It is interesting to note that generally ALS does not affect involuntary/smooth muscles such as those in the heart, esophagus, stomach and bronchi. This is why hearing, smell, sight and touch senses in an ALS patient generally remain normal. However, losing the ability to move for a prolonged amount of time may cause an indirect impact on involuntary muscles.