Figure 4. The fast sodium and slow calcium channels. The fast channel is in its "resting" mode;
the slow channel is in its depolarization mode, ie. active state (Ca++ ions moving through). The black dot indicates Nifedipine attachment site.
TTX = Tetrodotoxin, Nifedipine = a medically-used Ca++ channel blocker.
"m" and "h" are upper and lower gates in the Na+ channel.
"d" and "f" are upper and lower gates in the Ca++ channel.
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