Question

During the rising phase of an action potential, voltage-gated sodium channels open (activate) in response to depolarization. There is a net movement of sodium ions into the neuron causing the membrane to depolarize further. This greater depolarization causes even more voltage-gated sodium channels to open (activate).

This phenomenon is an example of:

negative feedback loop

positive feedback loop

Answer 1

The phenomenon of voltage-gated sodium channels opening further in response to depolarization, leading to an increased inward flow of sodium ions, is an example of a positive feedback loop.

Step-by-step explanation:

When voltage-gated sodium channels open in response to depolarization of the neuron's membrane, it results in a further inflow of sodium ions, which causes a greater depolarization. This cascade effect where an initial change leads to further changes in the same direction is known as a positive feedback loop. The increasing depolarization triggers the opening of even more voltage-gated sodium channels, amplifying the effect until the action potential peaks. After this peak, mechanisms to reset the membrane potential, such as the opening of voltage-gated potassium channels and closure of sodium channels, come into play to prepare the neuron for the next potential action.