Zoology - Neural Control and Coordination Question with Solution | TestHub

The first channels to open are the sodium ion channels, which allow sodium ions to enter the cell. The resulting increase in positive charge inside the cell (up to about +40 $\mathrm{mV}$ ) starts the action potential. This is called the depolarization of the membrane. Potassium ion channels Related Theory Events that characterize the transmission of a nerve impulse. (Ref. to Fig. 25.7)