Fluid and Electrolytes made easy study notes.

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Fluid and Electrolytes


t State of equilibrium in internal environment of body, naturally maintained by adaptive responses that promote healthy survival

t Body fluids and electrolytes play an important role

Water Content of the Body

t Accounts for 60% of body weight in adult

t 70-80% of body weight in infant

t Varies with gender, body mass, and age


t Intracellular fluid (ICF)

t Extracellular fluid (ECF)

l Intravascular (plasma)

l Interstitial

t Transcellular

Intracellular Fluid (ICF)

t Fluid located within cells

t 42% of body weight

t Most prevalent cation is potassium (K+)

t Most prevalent anion is phosphate (PO4-)

Extracellular Fluid (ECF)

t Fluid spaces between cells (interstitial fluid) and the plasma space

t Interstitial

l Most prevalent anion is chloride (Cl-)

l Most prevalent cation is sodium (Na+)

l Expands and contracts

l 2/3 of ECF in interstitium

t Intravascular (IV)

l Within vascular space

l Measured with blood tests

l 1/3 of ECF

Transcellular Fluid

t Small but important fluid compartment

t Approximately 1L

t Includes fluid in

l Cerebrospinal fluid

l Gastrointestinal (GI) tract

l Pleural spaces

l Synovial spaces

l Peritoneal fluid spaces

Mechanisms Controlling Fluid and Electrolyte Movement

t Diffusion

o Movement of molecules from an area of high concentration to low concentration

o Occurs in liquids, solids, and gases

o Membrane separating two areas must be permeable to substance for diffusion to occur

t Facilitated diffusion

t Very similar to diffusion

t Specific carrier molecules involved to accelerate diffusion

t Active transport

o Process in which molecules move against concentration gradient

o Example: sodium-potassium pump

o ATP is energy source

t Osmosis

t Movement of water between two compartments by a membrane permeable to water but not to a solute

t Water moves from area of low solute concentration to...