Membrane Potentials and Action Potentials
Start with the big picture
At rest, a neuron’s membrane potential is typically about –70 mV. Potassium permeability strongly influences this value, while the Na⁺/K⁺ ATPase helps maintain the ion gradients that support it. The Nernst equation provides a way to calculate an individual ion’s equilibrium potential. When threshold is reached, an all-or-none action potential proceeds through depolarization, repolarization, and hyperpolarization before the membrane returns toward rest. Absolute and relative refractory periods describe when another action potential cannot occur or requires a stronger stimulus. Together, these concepts connect ion movement, membrane voltage, and the timing of electrical signals.
What you'll learn
- Describe how ion gradients and selective permeability contribute to resting membrane potential.
- Explain the role of the Na⁺/K⁺ ATPase in maintaining ion gradients.
- State what the Nernst equation calculates for a specific ion.
- Outline the phases of an action potential and their associated ion movements.
- Distinguish absolute from relative refractory periods.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
