Final answer:
Potassium channels are primarily responsible for returning the membrane potential to a negative value in a neuron after an action potential. They allow the outflow of K+, which assists in quickly repolarizing the neuron.
Step-by-step explanation:
What helps the membrane potential to return quickly to a negative value in a neuron after an action potential has occurred? The element that assists in this process is the Potassium channels.
After the depolarization phase of an action potential, where sodium ions rush into the neuron, there is a need to reset the membrane potential back to its resting negative state. This repolarization occurs when Potassium channels open, allowing potassium ions (K+) to flow out of the neuron. This outflow of positively charged potassium ions helps to quickly bring the membrane potential back to its negative value. The sodium-potassium pump also plays a role in maintaining the resting membrane potential, but its operation is more gradual and involves actively transporting sodium ions out and potassium ions into the cell using ATP.