Final answer:
The minimal voltage change that triggers Na+ voltage-gated channels and starts an action potential is the threshold voltage, typically at -55 mV.
Step-by-step explanation:
The minimum voltage change required for the activation of the Na+ voltage-gated channels and the generation of an action potential is known as the threshold voltage. When the membrane potential reaches around -55 mV, the activation gate of the voltage-gated Na+ channels opens, allowing Na+ ions to rush into the cell. This influx of positive ions causes the membrane potential to depolarize from its resting value of -70 mV, moving towards positive values, and an action potential is initiated if the threshold is reached. The action potential is a critical component in the transmission of electrical signals in the nervous system, functioning much like a battery that releases stored charge upon activation.