A Positive Feedback Loop Occurs When the Outcome of an Event

Multiple Choice

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) An initial flow of sodium ions into the neuron opens voltage-gated sodium channels, rapidly causing more sodium to enter.
B) Opening of voltage-gated sodium channels causes voltage-gated potassium channels to open and release potassium to the extracellular environment, slowly counteracting sodium influx.
C) The sodium-potassium pump exactly balances ion leaks by pumping three sodium and two potassium ions across the membrane.
D) The threshold potential is around -55mV.