Changes in Plasma Osmolarity

Changes in Body fluid osmolality is maintained by a process of osmoregulation at about 275-
295 mOsm/kg. (Note at 37°C osmolality (osmoles /kg) and osmolarity (osmoles / L)
are virtually identical). Even small changes in plasma osmolarity result in hormonal
changes that alter water uptake by the kidney and stimulate thirst. The hormonal
regulation of plasma osmolarity occurs in the late distal tubule and collecting duct
of the nephron.
It is important to realise the following, when trying to understand changes in
plasma osmolarity:
Disorders of water balance manifest as changes in body fluid osmolarity.
Symptoms reflect changes in plasma osmolarity.
The major cation of the ECF is sodium, thus changes in sodium ion concentration
occur. This is not a problem with sodium balance; changes in sodium balance affect
plasma volume (Session 4), but is a problem with osmolarity due to changes in
water balancBody fluid osmolality is maintained by a process of osmoregulation at about 275-
295 mOsm/kg. (Note at 37°C osmolality (osmoles /kg) and osmolarity (osmoles / L)
are virtually identical). Even small changes in plasma osmolarity result in hormonal
changes that alter water uptake by the kidney and stimulate thirst. The hormonal
regulation of plasma osmolarity occurs in the late distal tubule and collecting duct
of the nephron.
It is important to realise the following, when trying to understand changes in
plasma osmolarity:
Disorders of water balance manifest as changes in body fluid osmolarity.
Symptoms reflect changes in plasma osmolarity.
The major cation of the ECF is sodium, thus changes in sodium ion concentration
occur. This is not a problem with sodium balance; changes in sodium balance affect
plasma volume (Session 4), but is a problem with osmolarity due to changes in
water balance. e. Plasma Osmolarity