Answer:
Multiple Sclerosis
Explanation:
Multiple Sclerosis is a potentially disabling disease of the brain and spinal cord (central nervous system).
Answer:
True
Explanation:
Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
