Final answer:
The peak positive potential during an action potential is generated by the permeability to sodium ions (Na+), which enter the cell through voltage-gated sodium channels, causing depolarization.
Step-by-step explanation:
The permeability to sodium ions (Na+) is most important for generating the peak positive potential during an action potential. At the onset of an action potential, voltage-gated sodium channels open, allowing Na+ to rush into the neuron. This causes a rapid rise in the membrane potential, creating a positive spike known as the peak of the action potential. Following this peak, these sodium channels close, and voltage-gated potassium channels open, leading to the efflux of K+, which helps to repolarize the membrane, returning it to its resting state. This coordinated opening and closing of Na+ and K+ channels are essential for the propagation of action potentials along the axon, enabling neural communication.
Additionally, the sodium-potassium pump (Na+/K+ transporter) actively maintains the resting membrane potential by moving Na+ out of and K+ into the cell against their respective concentration gradients, using ATP as an energy source. This pump is crucial for resetting the concentrations of Na+ and K+ after each action potential, ensuring that the neuron is ready for subsequent firing.