This document discusses fluid and electrolyte movements in the body through processes like osmosis, diffusion, filtration, and active transport. It defines key terms like osmosis, osmotic pressure, oncotic pressure, and tonicity. Osmosis occurs when water moves through a membrane from an area of lower solute concentration to higher concentration until concentrations are equal. Filtration allows fluids to move from the intravascular to interstitial compartments based on hydrostatic pressure gradients. The sodium-potassium pump actively transports sodium out of and potassium into cells against concentration gradients by expending energy.