Hi,

I'm a medical student, and one thing I've learned in med school is
that doctors often employ explanations that have little basis in fact
or logic.  One example that's really got me perplexed is that giving
someone calcium supposedly helps 'stabilize the membranes' of the
heart.  Now, you hear this *all the time* in medicine, and as a former
PhD in Physiology, this strikes me as a lot of hand waving.  Can you
provide a more precise explanation of the role of calcium in
protecting the heart under conditions of stress, e.g. with
hyperkalemia?  Don't hesitate to refer to channels, voltages, reversal
potentials, etc -- I'm looking for the real mechanism here. Thanks,
comments welcome.

well the heart uses extracellular calcium ions in muscle coctraction,
so if there was a calcium deficency it would put stress on the cardiac
muscles as they try to contract in responce to the action potentials
from the SA node, so conversly, if there is a rich supply then there
is very little/no stress put on the muscles