Flashcards in Lecute 7: Body Fluids Deck (24):
How is the Total Body Water monitored?
By homeostatic mechanisms
What are organs bathed in?
what does the external fluid do for organs?
What is ICF?
Interstitial fluid is the fluid inside cells
What is ECF?
Extracellular fluid is comprised of plasma, interstitial fluid and other ECF
What are the body fluid compartments seperated by?
A selectively permeable membrane
What determines the composition of each fluid?
The properties of the membranes
What is osmosis?
The movement of water molecules from a high concentration to low concentration through a selectively permeable membrane
The membrane is permeable to water but not to -insert word here-
Sodium (Na+) and Chloride (CL-)
What does water follow?
Water follows the solute (Na+)
What is the osmolarity of biological solutions dictated by?
The total number of osmotically active particles present
How do epithelial sheets move water between different body fluid compartments?
By first transporting solutes like sodium (Na+) so that water follows
What is the molarity for a substance that doesn't ionise or dissociate? Give an example
The molarity and osmolarity are equal. Osmolarity = Molarity e.g. Glucose
What's the molarity for substances that do ionise or dissociate? Give an example
Osmolarity = ~2x Molarity e.g. NaCL = Na+ and CL-
Hypotonic and its consequence
There is a higher concentration of particles on the inside of the cell than the outside. The cell will take in water and possibly burst
Hypertonic and its consequence
There is a higher concentration of particles on the outside of the cell and a lower concentration on the inside. The cell will shrivel up
Isotonic and its consequence
The concentration of particles are equal on both sides. There is no net movement of water and the cell will not shrink or burst
Describe the steps of the sodium-potassium pump
Na+ binds to pump, stimulates phosphorylation, proteins change conformation and expell Na+, K+ binds and releases phosphate, original conformation of protein restored, K+ released and Na+ sites are receptive, repeat.
Movement of 2 molecules simultaneously across a membrane in the same direction.
Transportation of 2 molecules in opposite directions.
What is the importance of the sodium-potassium pump?
It is electrogenic. It prevents cells from swelling, responsible for maintaining concentration differences and generating signals along merves and muscles.
Why are Ca2+ levels maintained at a very low concentration in the cytosol of mammalian cells?
Ions that are extensively used in the cell would form insoluble salts with calcium and the cell would calcify.
What mechanisms have cells evolved to maintain these low Ca2+ levels?
Active transport of Ca2+ out of the cell or active transport to intracellular conpartments like the ER/Mitochondria