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The ion pump most relevant to the action potential is the sodium–potassium pump, which transports three sodium ions out of the cell and two potassium ions in. [13] [14] As a consequence, the concentration of potassium ions K + inside the neuron is roughly 30-fold larger than the outside concentration, whereas the sodium concentration outside ...
The Na + /K +-ATPase, as well as effects of diffusion of the involved ions, are major mechanisms to maintain the resting potential across the membranes of animal cells.. The relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage), as opposed to the specific dynamic electrochemical phenomena called action potential and graded ...
Potassium is the major cation (K +, a positive ion) inside animal cells, while sodium (Na +) is the major cation outside animal cells.The difference between the concentrations of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential.
Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na +), potassium (K +), calcium (Ca 2+), and chloride (Cl −) ions have been identified. [1] The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane. [2]
Since Na + ions are in higher concentrations outside of the cell, the concentration and voltage differences both drive them into the cell when Na + channels open. Depolarization opens both the sodium and potassium channels in the membrane, allowing the ions to flow into and out of the axon, respectively.
This combination of closed sodium channels and open potassium channels leads to the neuron re-polarizing and becoming negative again. The neuron continues to re-polarize until the cell reaches ~ –75 mV, [2] which is the equilibrium potential of potassium ions. This is the point at which the neuron is hyperpolarized, between –70 mV and –75 mV.
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The equilibrium potential for an ion is the membrane potential at which there is no net movement of the ion. [1] [2] [3] The flow of any inorganic ion, such as Na + or K +, through an ion channel (since membranes are normally impermeable to ions) is driven by the electrochemical gradient for that ion.