Voltage-gated sodium channels

Question

I was wondering if a neuron would fire more often or less often than normal if the voltage-gated sodium channels lift their gates at -65mV instead of -55mV?

Answer 1

If voltage-gated sodium channels open at -65 mV instead of the usual -55 mV, the neuron would fire more often than normal.



Normally, the neuron's resting membrane potential is around -70 mV. The threshold for triggering an action potential is usually around -55 mV. If the channels open at -65 mV, the neuron will reach this threshold more easily, meaning smaller stimuli will trigger action potentials. This lower threshold makes the neuron more excitable, leading to more frequent firing in response to stimuli that wouldn't normally reach the standard threshold of -55 mV.

Answer 2

Hello!

The excitability of a cell depends on how easy it is for the cell to reach threshold from resting membrane potential (RMP). Threshold is the minimum voltage needed to activate voltage-gated sodium channels.

If threshold is farther from RMP, then it will be harder for the cell to reach threshold, and it will be less excitable. If threshold is closer to RMP, then it will be easier for the cell to reach threshold, so it will be more excitable.

Resting membrane potential is typically around -70mV, and threshold is typically -55mV. If voltage-gated sodium channels open at -65mV instead, I realize the threshold is more negative and therefore closer to RMP. Because it is closer, I know that it will take less stimulation for the voltage to go from RMP to reach threshold, so it is more excitable.

Belated, but I hope that helped. Best of luck studying for physiology!