IB Diploma Biology Practice Test 2026 – Complete Exam Prep

During hyperpolarization, a neuron's membrane potential becomes more negative than its resting potential. This change occurs when potassium ions continue to flow out of the neuron or when chloride ions enter, making it more difficult for the neuron to reach the threshold needed to initiate an action potential.

As a result, the neuron's ability to generate an action potential decreases during hyperpolarization. Since the membrane is further from the threshold, it requires a stronger stimulus to prompt the voltage-gated sodium channels to open, which is necessary for the depolarization phase of an action potential. Hyperpolarization effectively makes the neuron less excitable, reflecting a reduced likelihood of firing an action potential in response to incoming signals.