Re: Sodium homeostasis... was Re: tears

30 Oct 1995 22:10:57 GMT

J. Moore ( sez:

`The problem for the body, in terms of excreting of sodium (or
`potassium, etc.), is maintaining a balance (homeostasis) of water
`and sodium (or potassium, etc.). If an excreted solution has the
`same ratio of sodium to water as is in plasma, it doesn't change
`this balance, and the organ excreting this solution is not going
`to be able to rid the body of excess sodium. The solution itself
`is said to be isotonic. This is the situation with human tears.

`Human sweating excretes a substance which is hypotonic, having a
`lower ratio of sodium to water than is in plasma. Here too, the
`solution is not useful at ridding the body of excess sodium --
`quite the opposite -- since the body is eliminating proportionately
`more water than sodium from its plasma as it sweats.

Nevertheless, electrolyte loss through sweating is a problem,
because people drink fresh water to replenish their fluid loss,
so the net result is a constant fluid content, with fewer salts.
Thus the advent of electrolytically balanced drinks for athletes.

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