Describe the regulation of sodium in the body. 

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College Answer

This question was generally poorly answered. Total body sodium is regulated within 2% in 
normal individuals. The vast majority is contained in the extracellular compartment. While any 
physiological regulation involves a balance of input and output, sodium intake is essentially 
unregulated in humans. Output is regulated via renal, gastrointestinal and skin losses. Candidates 
needed to present the renal handling of Na including hormonal control and present factual 
knowledge about the level of absorption and GFR effects to attain a pass mark. Many candidates 
focused on osmolality and tonicity and some on the use of diuretics thereby not gaining marks 
on regulation of sodium. Most candidates didn’t mention either the skin and GIT role in sodium 
balance.