<prompt> Which event will NOT occur during depolarization phase?Na channels openCa channels openK channels openNone of the above  <response>: Na channels open, increasing the permeability of the cell membrane to Na. Sodiumions then diffuse into the cell, causing depolarization. This causes K channels to close quickly, decreasing the permeability of the cell membrane to K. The decreased diffusion of Kout of the cell also causes depolarization. Ca2 channels slowly open, increasing the permeability of cell membrane to Ca2. Calcium ions then diffuse into the cell and cause depolarization. 