What is the approximate threshold potential commonly cited for triggering an action potential in neurons?

What is the approximate threshold potential commonly cited for triggering an action potential in neurons?

• A. -70 mV
• B. -40 mV
• C. 0 mV
• D. -50 mV

Answer: (D)

Threshold is the depolarization level at which the action potential is triggered. For many neurons, the resting potential sits around -70 mV, and depolarizing to about -50 mV opens enough voltage-gated Na+ channels to start the rapid, self-reinforcing influx of Na+ that drives the spike. That’s why -50 mV is commonly cited as the threshold. If the depolarization doesn’t reach this level, the stimulus remains subthreshold and no action potential occurs. Resting at -70 mV would not trigger an AP, and 0 mV is far beyond the threshold and represents the spike phase rather than its initiation.

Threshold is the depolarization level at which the action potential is triggered. For many neurons, the resting potential sits around -70 mV, and depolarizing to about -50 mV opens enough voltage-gated Na+ channels to start the rapid, self-reinforcing influx of Na+ that drives the spike. That’s why -50 mV is commonly cited as the threshold. If the depolarization doesn’t reach this level, the stimulus remains subthreshold and no action potential occurs. Resting at -70 mV would not trigger an AP, and 0 mV is far beyond the threshold and represents the spike phase rather than its initiation.