-Being polarized means that the electrical charge on the outside of the membrane is positive while the electrical charge on the inside of the membrane is negative.
-Reasons for that are;
- The outside of the cell contains excess sodium ions (Na+); the inside of the cell although contains excess potassium ions (K+),which are positive,there are excess of negatively charged proteins and nucleic acid molecules.
- There are Na+/K+ pumps on the membrane that pump the Na+ back outside and the K+ back inside,this ensures that the outside of membrane is always positively charged at rest.
- Although the concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through ion channels ,eg at rest, potassium ions (K+) can cross through the membrane easily,while at rest, chloride ions (Cl-)and sodium ions (Na+) have a more difficult time crossing and the negatively charged protein molecules (A-) inside the neuron cannot cross the membrane.
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