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The resting membrane potential is balanced by ion leakage and ion pumping, to get an electrical signal started the membrane potential has to lose its balance. This starts with a membrane channel opening for Na+ since Na+ concentration is higher outside the cell, ions will rush into the cell. This will change the relative voltage inside the cell. The resting potential has a voltage of -70 mV, the sodium cation entering the cell cause it to become less negative. This is known as depolarization.

The concentration gradient for Na+ will continue to enter the cell making the voltage to become positive reaching +30 mV. At the same time, this happens, other voltage-gated channels are also opening, a concentration gradient acts on K+, as well, as it leaves the cell, it takes a positive charge with it making the membrane potential to move back to its resting voltage of -70 mV. This is called repolarization.

For potassium ions to reach equilibrium the membrane voltage needs to be below -70 mV, this leads to a period of hyperpolarization that occurs while the K+ channels are open.

I annexed an image that illustrates this action potential process.

Considering the information given during depolarization there's an increase in the number of sodium leak channels (7) making the inside of the cell more positive (2) increase in the membrane potential (4), this also implies a decrease in the extracellular concentration of potassium (6)

Meanwhile, during hyperpolarization an increase in the extracellular concentration of potassium (3) decreases the membrane potential (1) making the inside of the cell more negative (5).

I hope you find this information useful and interesting! Good luck!

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3 years ago