39.4 Explain how the neuron develops and maintains a resting potential. • Neurons use electrical signals to transmit information. In a resting neuron, one that is not transmitting an impulse, the inner surface of the plasma membrane is negatively charged compared with the outside; the membrane is polarized . • The resting potential is the potential difference of about -70 mV that exists across the membrane. • Ions pass through specific passive ion channels . K+ leaks out more readily than Na+ can leak in. • The gradients that determine the resting potential are maintained by ATP-requiring sodium-potassium pumps that continuously transport three sodium ions out of the neuron for every two potassium ions coming in. 39. 5 Compare a graded potential with an action potential . • If a stimulus causes the membrane to become less negative, the membrane becomes depolarized . If the membrane potential becomes more negative, the membrane is hyperpolarized . • A
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