Chapter 19, Problem 3CAL

Summary Introduction

Introduction:

When voltage-gated sodium ion channels open on a nodal cell temporarily, sodium increases the RMP of cells to its threshold value ( $\text{-40 mV}$). This, in turn, opens the voltage-gated calcium ion channels that push the RMP to $\text{0}\text{mV}$, that depolarizing the cell. The cell repolarizes again, when the voltage-gated calcium ion channels are closed, potassium channels are opened and sodium channels are reopened. It leads to a change in the action potential and rearranging the cell for another quick cycle ( $\text{0}\text{.8 seconds}$).