Complete each statement by using the appropriate word or phrase from the list. Then place the statements in the order of an action potential repolarization event.
1. Through the activated channels, ___ now flows outwards causing the membrane to repolarize back towards RMP.
2. As the membrane potential _, the voltage-regulated sodium channels begin closing which in turn reduces the sodium movement to the ICF
3. With a larger duration of activation than sodium channels, the potassium channels allow for a greater movement of potassium to the ECF causing a short period of_.
4. With membrane potentials approaching +35 mV, the _______channels become fully activated.
a. Sodium
b. Voltage regulate sodium
c. Potassium
d. Rises towards zero
e. Hyperpolarization
f. Voltage regulated potassium

Membrane potential can be defined as the difference in electric charges inside and outside of a cell. The resting membrane potential (RMP) occurs when there is no net current across the membrane and therefore the cell is in a non-excited state. At the RMP, sodium ions (Na+) are more concentrated inside the extracellular fluid (ECF) than inside the intracellular fluid (ICF), while potassium ions (K+) are more concentrated inside the ICF. The diffusion of K+ outside the cell triggers its hyperpolarization, by becoming the membrane potential more negative compared to the resting potential. As the potential nears +35 mV, the voltage-regulated potassium channels are open, thereby K+ ions leave the cell down its concentration gradient, while voltage-gated Na+ channels become saturated and inactivate.