Flashcards in Physio Deck (31):
Why can't albumin fit through the plasma membrane?
1. (-) charge
What are cells that lack direct communication with external environment? And what do they do?
1. heart and blood vessels: deliver O and nutrients
2. liver and kidneys: remove wastes and toxins
3. N.S.: monitor and regulate the organ system
**semi permeable membranes are what keep these systems separate
what is the equation for total body weight?
TBW= ECF (33%) + ICF (67%)
ECF: is made up of blood plasma and interstitial fluid which bathes cells
ICF: intracellular fluid
what is the volume of distribution?
the total volume that substance distributes after injection
-this is totally dependent upon the property of the substance
what are the different body compartments and what separates them?
blood plasma---BLOOD CAPILLARY WALLS--->interstitial fluid---CELL MEMBRANES---> Intracellular fluid
dilution principle and tracers
this principle can be used to determine the SIZE of a fluid in a compartment
-one uses the tracer because it distributes uniformly into the compartment of interest
what does tritium oxide measure?
total body weight
what does mannitol measure?
what does evans blue dye measure?
age/organs and water content
-water content decreases with age
-and different organs have different water contents kidney and heart have a lot
what is whole blood volume?
cells + plasma (ECF)
what is hematocrit?
% of blood vol. made up by cells
how does one derive total blood volume?
TBV= plasma volume x100/ (100-hematocrit)
what is simple diffusion?
when MEMBRANE PERMEABLE solutes move from high concentration to low [ ]
-only small and uncharged
ex: O2, CO2, NO, water
what is facilitated diffusion?
-only transport solutes DOWN an gradient
ex. RBC--glucose transporters: only if [ ] outside is greater than inside **ONLY IN RBCs**
**aquaporins--move water more rapidly through membrane
what is primary active transport?
-transport AGAINST gradient
-energy is required (ATP)
what is the Na-K-ATPase Transporter? What does this have to do with osmolarity?
-it is present in all cells
-3 Na out of cell
-2 K into the cell... making the cell slightly negative
-because there is more negative charge inside the cell, there may be more osmotically active particles in the cell than out
-This transporter is very important for reducing osmotic particles inside the cell --> so that they don't burst!
What is secondary active transport?
-energy isn't DIRECTLY linked to ATP
-uses one gradient to power another
What is co transport?
-it is a type of secondary transport
-both molecule are moving in the same direction
ex. Na--amino acid transporter
Na--glucose transporter: this pump works no matter what the glucose [ ] is outside of the cell
What is counter transport?
-type of secondary
-moving in opposite directions
ex. Ca-Na exchanger
-bilayer membranes are permeable to water
-flow of water from low to high [solutes]
-movement is due to differences in osmotic pressure between the 2 compartments
What is osmotic pressure? How is it calculated?
=the pressure that would be needed to externally prevent migration of water across the membrane
-it is a colligative property
What is Osmolarity? What is it determined by? What is the normal for body fluids?
-determined by the # of dissolved solute particles
= the [ ] of all particles
-Na is a major player in determining this of ECF
-ALL body fluids have the same ~290 mOsm/L
what is a reflection coefficient?
-it is dependent upon what the membrane deflects back
-water can move through so for water its 0
-albumin cannot move through so for that its 1
-it is dependent on size AND charge
What is tonicity?
=describes the tendency of an external solution to resist expansion of an intracellular volume
isotonic, hypertonic, hypotonic
-this is in relation to the the solutes in solution
isotonic= same [ ] of solutes outside and inside
hypertonic= more solutes outside, water exits and cell will shrink
hypotonic= more water outside than inside the cell, water enters the cell --> burst!
What are some IV solutions used for tx of things?
1. 154 mM NaCl-isosmotic, used in surgeries to replace plasma volume
2. 300 mM D glucose aka dextrose, isosmotic, used to tx hypernatremia
What is HYPERnatremia?
-high [ ] of Na outside of the cells
-most often due to lack of free water
tx: Dextrose 5%
enters body cells by facilitated diffusion --> CO2 and water
What is HYPOnatremia?
-excess water will result in this
-decreased Na in ECF
-swelling, arrhythmia, other things assoc. with imbalanced Na
What should one drink after 60 min. of vigorous exercise?
-gatorade OR fruit juice which will replenish carbs
*always drink in moderation though... bc can lead to hyponatremia