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The chief positive intracellular ion in a resting neuron is a potassium ion. Just inside the cell of a resting neuron, the membrane is negative.
Potassium.
sodium-potassium pump
The chief positive intracellular ion in a resting neuron is potassium (K+). At rest, the neuron has a higher concentration of K+ inside its cell membrane compared to outside. This creates a negative membrane potential, which is crucial for maintaining the resting state of the neuron.
repolarization
repolarization
Potassium ions (K+) are found in high concentration inside the neuron compared to outside. This concentration gradient is maintained by the sodium-potassium pump.
potassium ions
Opening of potassium channels allows potassium ions to move out of the neuron, leading to hyperpolarization by increasing the negative charge inside the neuron. This action increases the charge difference across the membrane, known as the resting membrane potential, making the neuron less likely to fire an action potential.
The main ions found inside a neuron are potassium and organic anions. The organic anions cannot cross the cell membrane but potassium ions can. It is the diffusion of potassium ions out of the cell which is the main cause of the resting membrane potential.
To maintain its resting potential, a neuron uses an active transport mechanism known as the sodium-potassium pump (Na+/K+ pump). This pump actively transports sodium ions (Na+) out of the neuron and potassium ions (K+) into the neuron, typically in a ratio of three sodium ions out for every two potassium ions in. This movement helps establish and maintain the negative charge inside the neuron relative to the outside environment, which is essential for the neuron's ability to transmit signals.
As potassium leaves the neuron, the inside of the cell will become progressively more negative, which will attract the positive potassium ions, preventing further exodus. If this electrical force is great enough, it will actually draw potassium ions from the outside of the cell back inside.