Select ALL statements that correctly describe events that occur during an action potential. a. Sodium-potassium pumps are activated when the membrane potential difference overshoots the resting potential. b. When voltage-gated Na channels are open, voltage-gated K channels are closed. c. When voltage-gated K channels are open, potassium ions (K ) move out of a neuron. d. Sodium ions (Na ) move out of a neuron in the first phase of an action potential, and then flow back into a neuron at the end of an action potential. e. Opening of voltage-gated Na channels causes more voltage-gated Na channels to open. f. Reaching the peak membrane potential reversal inactivates voltage-gated K channels.