Check/help me with my answers PLEASE?

Could someone help/check these answers for me?


The myelin sheath on a neuron allows nerve impulses to be faster because

A. neurotransmitter molecules are released in greater amounts.

B. the myelin sheath covers the entire axon.

C. nerve impulses jump from node to node as they move down the axon.

D. the threshold is met much faster.

During a knee-jerk reflex the nerve impulse is received by the

A. thalamus.

B. brain.

C. spinal cord.

D. spinal cord then the brain.

^I think its C.

What happens when the spinal cord is injured?

A. The parts of the body using the damaged areas lose sensation.

B. The affected neurons in the CNS regenerate gradually.

C. The path of impulses in the nervous system may be disrupted.

D. Both (A) and (C).

^I think its A.

Divers instinctively prevent serious damage to arms and legs by pulling them in close to the body during a dive. Which two organ systems work together to accomplish this?

A. digestive and circulatory systems

B. muscular and digestive systems

C. nervous and muscular systems

D. circulatory and nervous systems


for the first answer, i believe it is d. for the second answer i believe it could be b because the brain usually receives messages before the body. for the third answer b is ruled out since the nerves can't regenerate fast enough. it is both a and c. for the fourth answer it's c.