Question

Does amyotrophic lateral sclerosis (ALS) damage upper or lower motoneurons?

1) Upper motoneurons
2) Lower motoneurons
3) Both upper and lower motoneurons
4) Cannot be determined

Answer 1

ALS damages both upper and lower motoneurons, causing muscle weakness and paralysis.

Step-by-step explanation:

The correct answer is 3) Both upper and lower motoneurons.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that affects both upper motoneurons and lower motoneurons. Upper motoneurons are located in the cerebral cortex and provide input to lower motoneurons, which are located in the brainstem and spinal cord. In ALS, both types of motoneurons degenerate, leading to muscle weakness and eventually paralysis.

In a person with a motor disorder who cannot move their arm voluntarily but still has muscle tone, it is likely that both the upper and lower motoneurons are affected. This is because the ability to move the arm voluntarily involves both types of motoneurons working together to send signals from the brain to the muscles.

Therefore, the presence of muscle tone in this scenario suggests that the muscles still have some input from the upper motoneurons, but the ability to move the arm voluntarily is impaired due to the degeneration of both the upper and lower motoneurons.