A positive feedback loop occurs when the outcome of an event causes the event to continue occurring and amplifies its effects. Which of the following aspects of an action potential constitutes a positive feedback loop?
A. Opening of voltage-gated sodium channels causes voltage-gated potassium channels to open and release potassium to the extracellular environment, slowly counteracting sodium influx.
B. The sodium-potassium pump exactly balances ion leaks by pumping three sodium and two potassium ions across the membrane.
C. An initial flow of sodium ions into the neuron opens voltage-gated sodium channels, rapidly causing more sodium to enter.
D. The threshold potential is around -55mV.
Answer: C
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