What is the resting electrical threshold potential required to trigger an all-or-none action potential in human axons?
Answer and explanation
Correct answer: A. -55 millivolts (mV)
- Step 1: A resting neuron sits at -70 mV. Incoming excitatory stimuli cause graded depolarizations. Step 2. Once the membrane potential depolarizes to threshold (-55 mV), voltage-gated Na+ channels open rapidly in a positive feedback loop, generating an action potential. Answer: -55 millivolts (mV). Why not the others: 0 mV is complete depolarization; -70 mV is the resting potential; +30 mV is the peak overshoot potential.
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