Final answer:
Hyperpolarization of the postsynaptic membrane results in the membrane potential becoming more negative than the resting potential due to the delayed closing of potassium channels after repolarization.
Step-by-step explanation:
During hyperpolarization of the postsynaptic membrane, the membrane potential becomes more negative. This occurs after the cell reaches the peak of an action potential. Initially, sodium ions (Na+) enter the cell causing depolarization and a positive spike in membrane potential. Following this, potassium ions (K+) exit the cell, leading to repolarization where the membrane potential returns towards a negative value. As the K+ channels are slightly delayed in closing, the membrane potential overshoots the resting potential, causing it to become more negative than the resting potential, which is the state of hyperpolarization.
During this phase, the membrane potential may reach values lower than the usual resting potential of approximately -70 mV. This process is critical for resetting the neuronal membrane in preparation for potential subsequent action potentials. The neuron then returns to its resting potential due to the activity of non-gated ion channels and the Na+/K+ pump which manages the concentration gradients of sodium and potassium across the membrane.