acid
Any substance capable of releasing hydrogen ions in solution
active transport
Movement of substances across a cell membrane against an electrochemical gradient
anions
Negatively charged ions
ascites
Accumulation of serous fluid in the peritoneum
baroreceptors
Stretch receptors located in major arteries and veins that monitor vascular volume
base (or alkali)
Any substance that can combine with and decrease hydrogen ions in solution; alkali
buffers
Compounds that help stabilize the pH of a solution by neutralizing added acid or base
cations
Positively charged ions
diffusion
Movement of molecules from an area of higher concentration to one of lower concentration
electrolytes
Chemical compounds that dissociate into ions when in solution; usually refers to extracellular sodium, potassium, and chloride
extracellular fluid
Body fluid outside the cells; mainly interstitial fluid and plasma
filtration
Passage of a solution through a semipermeable membrane from a region of higher pressure to a region of lower pressure
hyperosmolar
One compartment contains a greater concentration of a dissolved substance (hyperosmolar) than the other compartment (hypoosmolar)
hypertonic
Of greater concentration than in body fluids
hypoosmolar
One compartment contains a lesser concentration of a dissolved substance (hypoosmolar) than the other compartment (hyperosmolar)
hypotonic
Of lower concentration than in body fluids
interstitial fluid
Fluid between the cells
intracellular fluid
Portion of body fluid contained within the cells
intravascular fluid
Fluid inside the blood and lymphatic vessels
ions
Charged particles formed by the dissociation of electrolytes in a solution
milliequivalent
Unit used to give the concentration of an electrolyte in solution; commonly expressed as mEq/L
osmolality
Concentration of solutes in a solution, expressed as milliosmols per kilogram
osmolarity
Concentration of solutes in a solution expressed as milliosmols per liter
osmosis
Movement of a fluid through a semipermeable membrane from a region of lower to higher solute concentration
osmotic pressure
Pressure exerted by nondiffusible particles in a solution across a semipermeable membrane; tends to hold fluid within its container and is opposed by hydrostatic pressure
tonicity
Fluid's effect on cell size