FLUIDS - Fluid transport and Fluid Administration Flashcards
What is diffusion?
Movement of solutes from a high to low concentration down their electrochemical gradient
What are the methods of solute diffusion across a membrane?
Diffusion across the lipid bilayer
Diffusion through protein channels
Facilitated diffusion
What is Ficks law?
Ficks law defines the rate of diffusion using the solubility of the solute, the fluid concentration on either side of the membrane and membrane thickness
What is Net flux?
Diffusion is actually a two way process, net flux describes the movement of solutes down their concentration gradient
What is active transport?
An energy dependent process where the solute is moved against its electrochemical gradient
Describe the method of primary active transport
- Solute binds to an ATPase dependent protein
- ATP breaks down into ADP+P, causing a conformational change in the protein
- Solute is moved across the membrane against its concentration gradient
Describe the method of secondary active transport
The solute moves in association with another molecule/ion that is moving down its concentration gradient, utilising its stored chemical energy
What is bulk flow?
A passive process in which large numbers of ions, molecules and particles which have dissolved within a fluid, move together in the same direction down a pressure gradient
What is the Donnan’s effect?
The presence of a charged insoluble solute causes an uneven distribution of permeable solutes across a semi-permeable membrane
What is osmosis?
Osmosis is the net water movement from a low impermeable solute concentration to a high impermeable solute concentration across a semi-permeable membrane (movement of water down its concentration gradient)
What is osmolarity and how is it measured?
Osmolarity is the measure of solute concentration in a solution (the number of solute particles per litre of solution)
What is osmolality?
Osmolality is the number of solute particles per kg
What determines tonicity/tone?
The tone exerted by a solution is determined by the concentration of impermeable solutes in the solution, determining the net water movement across a semi-permeable membrane
Describe an isotonic solution
When the concentration of impermeable solutes between two solutions is the same (regardless of the concentration of permeable solutes); no net water movement
Describe a hypertonic solution
When comparing two solutions, a hypertonic solution contains more impermeable solutes than the other solution; net water movement into the hypertonic solution
Describe a hypotonic solution
When comparing two solutions, a hypotonic solution contains less impermeable solutes than the other solution; net water movement from the hypotonic solution
What are the percentages of total body water in animals and how does this differ with age and condition?
Neonatal: 75% total body water
Adult: 55-60% total body water
Old/obese: 45% total body water
Why does the percentage of total body water change with age and weight gain?
Total body water changes depending on fat distribution
Describe the distribution of fluid between the main body fluid compartments
Intracellular fluid (2/3 of body fluid)
Extracellular fluid (1/3 of body fluid)
What are the two major electrolytes contributing to the osmolarity of the intracellular fluid compartment?
K+
PO3-
What are the two major electrolytes contributing to the osmolarity of the extracellular fluid compartment?
Na+
Cl-
What is the function of Starling’s forces?
Starling’s forces act on all water molecules and regulate the fluid movement across the capillary wall
Describe the four Starlings forces
- Capillary hydrostatic pressure: moves water out of the capillary
- Interstitial hydrostatic pressure: moves water into the capillary
- Osmotic pressure: a pressure gradient generated by interstitial fluid proteins pulling water out of the capillary
- Oncotic pressure: a pressure gradient generated by plasma proteins pulling water into the capillary