Structure and Functions of Cells of the Nervous System - Communication Within a Neuron - The Membrane Potential

4 important questions on Structure and Functions of Cells of the Nervous System - Communication Within a Neuron - The Membrane Potential

What is the contribution of diffusion to establishing membrane potential?

Diffusion is the process of molecules distributing themselves evenly throughout the medium in which they are dissolved. Molecules will diffuse from regions of high concentration to regions of low concentration. Diffusion tends to push K+ out of the cell and push Cl-  and Na+ to the inside of the cell.

What is the contribution of electrostatic pressure to establishing membrane potential?

Electrolytes are substances which split into two ions, each with opposing electrical charge, when they are dissolved in water. Electrostatic pressure is the force exerted by the attraction or repulsion of anions(-) and cations(+). Electrostatic pressure moves ions to a place where the concentration is low and away from a place where the concentration is high. Electrostatic pressure tends to force K+ to the inside of the cell and Cl- to the outside of the cell. Since Na+ is positively charged, electrostatic pressure pulls it inside the cell.

What ions are in the extracellular fluid and what in the intracellular?

Organic anions are found only in the intracellular fluid.  Chloride (Cl-), sodium (Na+) and potassium (K+) are found in both the intracellular and the extracellular fluid. However, K+ is mostly found in the intracellular fluid and Cl- and Na+ are mostly found in the extracellular fluid (seawater).
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What is the function of the sodium-potassium pump in establishing membrane potential?

The sodium-potassium pump makes sure that the original concentration of the ions on the inside and the outside of the cell remains the same, despite diffusion and electrostatic pressure. It consists of a lot of protein molecules embedded in the membrane. They push 3 Na+ ions out for every 2 K+ ions in.

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