GENERAL HISTOLOGY

Detailed explanation-1: -That ion is Na+. The high concentration of Na+ outside the cell and relatively low concentration inside the cell results in a chemical (diffusional) driving force for Na+ influx. There is also an electrical driving force because the inside of the cell is negative and this negativity attracts the positive sodium ions.

Detailed explanation-2: -Ionic species are not distributed equally on the two sides of a nerve membrane. Na and Cl are more concentrated outside the cell while K and organic anions (organic acids and proteins) are more concentrated inside. The overall effect of this ionic distribution is the resting potential.

Detailed explanation-3: -At resting potential, the charge of the outside of the neuron is-70 mV and the inside is negatively charged. The sodium-potassium pump helps maintain the resting potential. The pump will move the sodium and potassium ions the cell while it moves two potassium ions into the cell.

Detailed explanation-4: -Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron. Remember, sodium has a positive charge, so the neuron becomes more positive and becomes depolarized.