Decadência do potencial de repouso

Resting potential is the stable electrical voltage across a neuron's membrane when it is not actively firing, typically around -70 millivolts. This negative charge inside the cell relative to outside is maintained by the sodium-potassium pump and is essential for neuronal excitability, allowing neurons to respond to stimuli and generate electrical signals.

The sodium-potassium pump actively transports three sodium ions out of the cell and two potassium ions into the cell using ATP energy. This unequal exchange creates and maintains the concentration gradients that establish the negative resting potential, compensating for passive ion leakage across the membrane.

Ion channels allow selective passive movement of ions across the membrane based on concentration and electrical gradients. The electrochemical gradient and channel proteins determine which ions flow and at what rate, with potassium channels being more permeable at rest, contributing to the negative resting potential.

Resting potential provides the baseline electrical state from which neurons can generate action potentials. When stimulated, the membrane depolarizes from resting potential toward threshold, triggering the rapid voltage changes characteristic of action potential phases of stimulation that propagate signals along the axon.

Without the sodium-potassium pump, sodium accumulates inside the cell and potassium leaks out, causing the resting potential to become less negative and eventually depolarize. The neuron loses its ability to maintain stable electrical conditions and cannot generate normal action potentials, impairing neuronal communication.

At rest, the neuronal membrane is more permeable to potassium than sodium because more potassium channels are open. Since potassium ions flow out of the cell down their concentration gradient, this outward movement of positive charge makes the inside more negative, establishing the characteristic negative resting potential.