When the body temperature drops, this has the effect of reducing the potential a

Question

When the body temperature drops, this has the effect of reducing the potential across the axonal membrane slightly. At a body temperature of 30°C, the potential difference is reduced from the standard 70 mV, down to 65 mV. For these conditions, the experimentally measured concentration of Na+ ions inside the lipid bilayer is 10E18 Na+ ions/cm3.

a) Compute the concentration of Na+ ions outside the lipid bilayer using only physical principles

b) Of on the other hand the experimentally measured concentration of Na+ ions outside the lipid bilayer turns out to be 1.6 E19 Na+ ions/cm3 in healthy neurons, What can you conclude is happening from a physiological point of view?

Explanation / Answer

a) difference in electrical potential from having more ions outside than inside would lead to a positive charge outside and a negative charge inside, thus causing sodium ions to migrate inward until the potential difference was canceled out.

Thus, outside concentration and the inside concentration are the same, at 1018 ions per cubic centimeter.

b) the experimentally measured concentration of ions is about 16 times larger than what the physical equilibrium would predict, something has to be breaking that equilibrium.

So to resist the effect of the electrical charge difference and forcing sodium ions to go outside even when electrostatic force is trying to pull them inward.

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