#1) during the rising phase of an action potential, incoming na+:

a)inactivates na+ channels.

b)hyperpolarizes the cell

c)depolarizes the cell.

d)often causes the membrane potential to "overshoot", going above 0 mv.

#2)

during the early portion of the falling phase of an action potential (ie: right after the "peak" of the ap), na+ channels:

a)are closed

b) are inactivated

c) permit na+ ions into the neuron.

d)
do not permit na+ ions into the neuron.

#3)

the refractory period goes from "absolute" to "relative" when:

the inactivation gate of na+ channels opens up.

the inactivation gate of na+ channels closes.

k+ channels begin to open.

k+ channels begin to close.

#4)

during the relative refractory period:

k+ channels are open.

na+ channels are inactivated.

it is impossible to fire a subsequent action potential.

it is more difficult, but possible, to elicit another action potential.