Animal Form and Function

A. Resting Potential and Action Potential Definition: Resting potential is the electrical potential difference across the plasma membrane of a neuron when it is not conducting an impulse, typically around -70mV. Action potential is the rapid, temporary reversal of membrane potential that travels along the axon as a nerve impulse. Explanation: Resting potential is maintained by the sodium-potassium pump which actively transports 3 Na+ ions out and 2 K+ ions into the cell, creating an electrochemical gradient. The membrane is more permeable to K+ than Na+, causing more positive ions to leave than enter. Action potential occurs when a stimulus opens voltage-gated Na+ channels, causing rapid Na+ influx that depolarizes the membrane to about +40mV. This triggers a wave of depolarization that propagates along the axon as the nerve impulse. The process involves sequential opening and closing of ion channels in a coordinated manner. Think of it as: Think of resting potential like a loaded spring - compressed and ready to release energy.