Thursday, March 12, 2009

Ca2+ and AP

This is the answer for 8atashiarase8 question in the shoutbox. The question is : Why hypercalcimea lead to weakness and hypocalcemia lead to tetanus?

Actually, Ca2+ plays a vital role in action potential conduction.

Ca2+ will bind with the Na+ channel protein molecule.

The +ve charges will alter the electrical state of the channel protein (alter voltage for opening Na+ channel)

It means that the Ca2+ will try to limit the opening of Na+ channel.

So, when there is low Ca2+, the nerves become more excitable. Why? It is because there is no control of the Na+ channel opening (since Ca2+ is low) and threshold to elicit an action potential is reduced. So, it is easily stimulated to be opened. This will lead to tetanus.

When the Ca2+ is high, the nerves become less excitable. Why? Because the presence of high Ca2+ will limit the opening of Na+ channel. So, there will be less opening of Na+ channel and action potential cannot be generated. This will lead to weakness.

Do inform me if there is any mistakes. Syukran.



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