Library · Physiology
Sodium balance
Make it clearer
Sodium is the body's salt, and it sits mostly outside the cells: it is the main solute of the extracellular fluid, meaning the dissolved particle that matters most in the fluid around the cells and in the blood.
The kidney is what keeps it where it belongs. Its job is to control how much of the fluid it has already filtered gets taken back, and hormones such as antidiuretic hormone and aldosterone can fine-tune that decision.
That capacity for adjustment is striking. Eating ten times more sodium than usual has been shown to change the concentration of sodium in the blood relatively little, because the kidney compensates.
Think of a drain with a gate that opens wider or narrows depending on what comes in. Balance also depends on how much fluid a person is carrying and on how well the heart is working.
In brief
Sodium is the main solute of the extracellular fluid and, with chloride, the main contributor to its osmolarity.
The kidney plays a major role by controlling how much fluid it reabsorbs from the glomerular filtrate, a process hormones such as antidiuretic hormone and aldosterone can modulate.
Its range of adjustment is enormous: ten times more dietary salt changes plasma sodium very little.
A drain with a gate that opens more or less depending on what comes in.
Balance also depends on volume status and on the heart.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingHyponatremia, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Osmoregulation and Excretion, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated