Final answer:
The movement of the membrane potential from -60 mV to -70 mV is known as hyperpolarization, which is a phase following repolarization in the action potential cycle.
Step-by-step explanation:
When the membrane potential moves from -60 mV to -70 mV, this process is called hyperpolarization. This occurs after repolarization and means that the membrane voltage not only returns to the resting membrane potential but overshoots it, becoming even more negative.
This is a part of the action potential, especially just after repolarization has brought the membrane potential back toward the resting value of -70 mV. As potassium (K+) channels remain open slightly longer, more K+ leaves the cell, resulting in an even more negative membrane potential before the resting state is restored.