Chapter 5: Membrane Dynamics Flashcards
What are the two body fluid compartments?
- cells (ICF)
* ECF - fluid that surrounds the cells
the buffer between the cells and outside environment
ECF
what makes up the ECF?
interstitial fluid
blood plasma
what state are the ICF and ECF in?
osmotic equilibrium
brought about by the free movement of water between the ICF and ECF, so the fluid concentrations are balanced on the two sides of the membrane
osmotic equilibrium
an uneven distribution of solutes between ICF and ECF
chemical disequilibrium
how is disequilibrium maintained?
Living cells use energy to maintain this state of disequilibrium
- the charge difference between the ICF and ECF
* can create electrical signals
electrical disequilibrium
osmotic, chemical, and electrical disequilibrium are considered what?
dynamic steady states
what is the goal of homeostasis?
to maintain the dynamic steady states of the body compartments
- solvent for all living cells
* can move freely in and out of cells by water-filed ion channels and special water channels
water
special water channels
aquaporins
why do women have less water/kg of body mass?
due to more adipose tissue which occupies most of the cell volume
what is the cell membrane composed of and in what amounts?
ICF - 2/3
ECF - 1/3
plasma - minimal
what is extracellular fluid made of and what amounts?
plasma -25%
interstitial fluid - 75%
the movement of water across a membrane in response to a solute concentration gradient
osmosis
in which direction does water move?
Water moves to dilute the more concentrated solution or from areas where it (water) is in higher concentrations to where it (water) is in lower concentrations
when does osmosis stop?
when there is no more net movement
- pressure that opposes the movement of water into a compartment
- Measured in atmospheres (atm) or (mmHg
osmotic pressure
how can osmosis be measured quantitatively?
- osmotic pressure
* concentrations of solutions
- concentrations are expressed as this
* number of moles of dissolved solute/L of solution
molarity
the number of osmotically active particles per liter of solution (osmol/L = OsM, or milliosmoles/L =mOsM)
osmolarity
concentration expressed as osmoles of solute per kilogram of water
osmolality
why is osmolality used clinically?
because it is easy to estimate peoples body water content by weighing them