Question

if this cell is a neuron, using the voltage clamp to change the cell membrane potential from -70.0 mv to -5.0 mv should cause:
a) a current that indicates a large amount of sodium briefly entering the cell
b) a current that indicates that sodium continues to enter the cell as long as the membrane potential is set to -5 mv
c) a current that indicates a large amount of sodium briefly leaving the cell
d) no change in sodium current cross the cell

Explanation:

When the membrane potential of a neuron is changed from -70.0 mV (resting potential) to -5.0 mV (depolarization), voltage - gated sodium channels open. Sodium ions (\(Na^{+}\)) rush into the cell due to the concentration gradient (higher \(Na^{+}\) outside the cell) and the electrical gradient (inside the cell is more negative at rest). However, sodium channels have an inactivation gate. After a short time (a few milliseconds), the inactivation gate closes, and sodium influx stops. So, there is a brief influx of sodium.

Answer:

A. A current that indicates a large amount of sodium briefly entering the cell