Sodium Homestasis
J. Moore (j#d#.moore@canrem.com)
Sun, 5 Nov 95 17:24:00 -0500
I almost sent off this message with a couple of critical typos, but I
believe I caught it before it went out. This is the corrected version:
The following is another primer on sodium and homeostasis:
>IB> Anything that gets rid of salt can be a salt excretion mechanism.
>IB> I agree that unless they wept a lot it would be ineffective,
>IB> certainly not as effective as kidneys or sweating but so what.
JM> >The problem for the body, in terms of excreting of sodium (or
JM> >potassium, etc.), is maintaining a balance (homeostasis) of water
JM> >and sodium (or potassium, etc.). If an excreted solution has the
JM> >same ratio of sodium to water as is in plasma, it doesn't change
JM> >this balance, and the organ excreting this solution is not going
JM> >to be able to rid the body of excess sodium. The solution itself
JM> >is said to be isotonic. This is the situation with human tears.
Cl> That is only true if you drink fluid that has the same ratio of
sodium
Cl> to water as plasma, e.g. Gatorade(tm). If you drink
Cl> water your salt content goes down, your water content stays the
same.
Cl> You loose salt.
<snipped>
Cl> Sweating certainly does remove salt from the body.
<snipped>
Cl> This has probably nothing to do with homind evolution, but sweating
does
Cl> eliminate salt. Not enough to allow you to drink seawater but
enough to
Cl> make you sick if you don't replace it.
Cl> Tom Clarke
And if you eat salty foods instead of drinking freshwater, you
gain salt in proportion to water... so what?
You are either obstinately grasping at straws or I have not expressed
the facts simply enough. On the chance that the latter is the case,
I will try to explain it again:
Your body must maintain, within a limited range, a certain balance
of water to sodium; maintaining such balances of water and various
electrolytes is called homeostasis. Homeostasis is the regulation
of the body's internal environment within somewhat narrow limits;
one example of homeostasis in the mammalian body is the regulation
of body temperature, another is osmoregulation, the regulation of
the makeup of bodily fluids. To maintain health, your body must
maintain such a balance, and to do so, it must have a mechanism
which is capable of ridding the body of excess sodium. This is
not something which is optional; it is necessary for continued
health and life.
If you drink lots of fresh water, and nothing else, your balance
of water to sodium leans toward less sodium.
If you eat salty foods or drink very salty water (like seawater),
your balance of water to sodium leans toward more sodium.
When you produce tears, you lose water and sodium in the same
proportions as it appears in your plasma. If you produce tears
and do not drink water or eat salty foods, your body's balance of
water to sodium does not change. Therefore tears *are not* capable
of ridding the body of excess sodium.
When you produce sweat, you lose proportionately more water than
sodium as compared to plasma. If you produce sweat and do not
drink water or eat salty foods, your body's balance of water to
sodium changes toward more sodium. Therefore sweat *is not* capable
of ridding the body of excess sodium.
When you produce urine, your renal system can alter the balance of
water and sodium so that, unlike either tears or sweat, you can
lose proportionately more sodium than water as compared to plasma.
Your renal system, unlike either tears or sweat, can alter your
body's balance of water to sodium toward *less* sodium. Therefore
the renal system, dramatically unlike either tears or sweat, *is*
capable of ridding the body of excess sodium.
Jim Moore (j#d#.moore@canrem.com)
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