What is the purpose of sodium in our bodies?

Hi Shackles,

Sodium is an important ion that is used by the body in several ways:

It helps with water balance in cells and the blood.
It is an important part of muscle contraction and relaxation.
It is one of the molecules that moves between nerves to cause a neural impulse.

Here are some sites for you:

http://www.feinberg.northwestern.edu/nutrition/factsheets/sodium.html
"Sodium is the primary electrolyte that regulates the extracellular
fluid levels in the body. Sodium is essential for hydration because
this mineral pumps water into the cell. In turn, potassium pumps the
by-products of cellular processes out of the cell, eventually
eliminating these "wastes" from the body.
In addition to maintaining water balance, sodium is necessary for
osmotic equilibrium, acid-base balance and regulation of plasma
volume, nerve impulses and muscle contractions."

http://il.essortment.com/whatissodium_rtlq.htm
"In the human body, sodium works in conjunction with potassium to
balance the body?s water. It also is integral to the conduction of
nerve impulses and the contraction of muscles. Without adeqaute levels
of sodium, normal heart rhythm cannot be maintained."

http://www.traceminerals.com/inorganic.html
"Sodium: Maintain water balance; maintain acid-base balance; muscle
contraction; nerve contraction."

http://www.biology.eku.edu/RITCHISO/301notes3.htm
"The nervous system 'communicates' with muscle via neuromuscular (also
called myoneural) junctions. These junctions (Figure 1) work very much
like a synapse between neurons. In other words:
the impulse arrives at the end bulb, 
chemical transmitter is released and diffuses across the neuromuscular cleft, 
the transmitter molecules fill receptor sites in the membrane of the
muscle & increase membrane permeability to sodium,
sodium then diffuses in & the membrane potential becomes less negative, 
and, if the threshold potential is reached, an action potential
occurs, an impulse travels along the muscle cell membrane, and the
muscle contracts."

I found these sites by searching the Google database for variations on
the following keywords:
human
human health
sodium
muscles and/or nerves
limited to site:.edu

I'll be working on some of your other sodium questions as well -
please let me know if I can clarify this or any of the others further!

Librariankt

Another question would be is the sodium in NaCl (salt, sodium
chloride) the same sodium that is in, say, hot dogs.  To digest food
you need hydrochloric acid..."chloric" = the chloride in sodium
chloride.  The moral of the story is salt your proteins but don't
consume tons of sodium by way of say, canned soup.