Voltage Clamping

Now that you have the basics down, answer the following questions about electrical circuits to learn about Voltage Clamping. The questions will get increasingly difficult; check the answer for each as you go, but don't check the answer until you think you have it.

1. If the current is held constant when the resistance decreases, what happens to the voltage?

2. If the voltage is held constant when the resistance decreases, what happens to the current?

3. If you can't directly measure resistance, but you can measure voltage and current, how could you calculate resistance?

Now some cellular questions.

In a cell membrane, ions can't go through the lipid part of the membrane. Resistance to ionic current (ions going into or out of the cell) is a function of the number of open channels in the cell's membrane. Channels are opened and closed by voltage.

4. What would happen to the current if you changed the voltage suddenly (opening channels) and then held it constant?

5. And here's the big question. If you want to measure the number of open channels in a membrane at a specific voltage, and you could control voltage and current, how would you do it?

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