4. Body Fluid Balance Flashcards
What is the main positively charged ion in the ECF?
Na+
What is the main negatively charged ion in the ECF?
Cl-
What is the main positively charged ion in the ICF?
K+
What are the main negatively charged ions in the ICF?
PO4^3-
Proteins
What is osmosis?
Movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration
What is osmotic pressure?
The pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis
What is an osmole?
Refers to the number of osmotically active particles in a solution
Define osmolarity
Osmotically effective conc when expressed in osmoles/litre
Define osmolality
Osmotically effective conc expressed in osmoles/kg
Describe the effects of dehydration
- Water content of ECF decreases causing increased ECF conc
- Osmolarity ECF increases
- Water leaves cells by osmosis
- Osmolarity ICF increases
- Disruption of cell function
Describe the effects of water retention
- Excess water dilutes ECF
- Osmolarity of ECF decreases
- Water moves by osmosis into cells
- Osmolarity ICF decreases
- Disruption of cell function
Define tonicity
Measure of the osmotic pressure gradient of two solutions separated by a semipermeable membrane
Crystalloids
Clear solutions given by IV
Sterile water and electrolyte solns
Why would an isotonic saline be given?
Given to dehydrated patients
Why would a hypertonic solution be given?
Plasma osmolarity is low
Cells are overhydrated
