Question

Polio is a virus that causes muscle paralysis, for example, former President Franklin D Roosevelt used a wheelchair after contracting polio when he was 39. However, this virus NEVER directly affects muscular tissue. (a) How would this virus paralyze skeletal muscle without directly affecting the muscle tissue? (b) This virus never causes paralysis of the heart… why would it not affect the heart if it does affect skeletal muscle?

Answer 1

* Polio virus(types P1,P2,P3) are members of enterovirus family which are mainly transferred from one person to other person by the oral contact or through feacal matter. * polio virus multiply in the specialized cells of intestine and invade central nervous system by entering into the blood stream. It spreads along nerve fibres which multiply in nervous system and destroy nerve cells(motor neurons) which activate skeletal muscles. * These nerve cells cannot regenerate and leads to failure of muscle function due to lack of enervation. Legs are mostly effected compared to arm muscles during the polio condition(poliomyelitis).

*The cardiac muscle has not that much effect by poliovirus as it is not directly innervated by the motorneurons of nervous system. They sysnapse onto neurons located in ganglia of the autonomic nervous system. Therefore the heart is not directly effected by the poliovirus. However, there are some complications are seen due to the effect of poliovirus.