check+ please+ thanks in advance?

Question

The refractory period of a neuron
A.is due to the high negative polarity of the inside of the neuron
B.occurs only during the repolarization phase
C.occurs only during the depolarization phase
D.occurs during depolarization and the repolarization phase

the asnwer is A


One way transmission of a nerve impulse across a synapse occurs because the

A.presynaptic membranes do not produce any transmitter chemicals
B.postsynaptic membranes do not produce any transmitter chemicals
C.presynaptic membranes produce more concentrated transmitter chemicals
D.postsynaptic membranes produce more concentrated transmitter chemicals

I believe the answer is:
actually not quite sure??

Answer 1

I'm not really sure either. But I'm going to use logic to answer your second question.

I think the answer is C. Chemistry tells us that chemicals diffuse away from a concentrated source. I know that transmitter chemicals must move across the synapse to achieve transmission. Answers A and B are not valid because they don't address the creation of the transmitter chemicals. Answer D is not logical because it would cause a "backward" flow if the postsynaptic membranes had more of the transmitter chemicals.
Hope this helps.