Controlling Movement Flashcards
ECF main cations
Mainly sodium with small amounts of potassium, calcium and magnesium
ECF main anions
Mainly chloride, with small amounts of bicarbonate, sulfate, and phosphate anions
ICF main cations
The main cation is potassium, with small amounts of magnesium and sodium.
ICF main anions
The main ICF anion is phosphate, with some protein and a small amount of bicarbonate.
Cations
Cations are positively charged ions. Examples include sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) ions
Anions
Anions are negatively charged ions. Examples include bicarbonate ( ), chloride (Cl − ), and phosphate ( ) ions. Most proteins bear a negative charge and thus are anions.
Electrolytes
Electrolytes are substances whose molecules dissociate, or split, into ions when placed in water. Electrolyte composition varies between ECF and ICF.
Ions
Ions are electrically charged particles
Diffusion
Diffusion is the movement of molecules from an area of high concentration to low concentration
Facilitated diffusion
Facilitated diffusion involves the use of a protein carrier in the cell membrane. The protein carrier combines with a molecule, especially one too large to pass easily through the cell membrane and helps move the molecule across the membrane from an area of high to low concentration.
An example of facilitated diffusion is glucose transport into the cell.
Active transport
Active transport is a process in which molecules move against the concentration gradient. External energy is needed for this process. An example is the sodium-potassium pump. The concentrations of sodium and potassium differ between the ICF and ECF.
Osmosis
Osmosis is the movement of water “down” a concentration gradient, that is, from a region of low solute concentration to one of high solute concentration, across a semipermeable membrane. Osmosis requires no outside energy sources. It stops when the concentration differences disappear or when hydrostatic pressure builds and opposes any further movement of water.
Osmolality
Osmolality measures the number of milliosmoles per kilogram of water or the concentration of molecules per weight of water. Osmolality is the preferred measure to evaluate the concentration of plasma, urine, and other body fluids.
Plasma osmolality
Normal plasma osmolality is between 280 and 295 mOsm/kg. A value greater than 295 mOsm/kg means that the concentration of solute is too great, or the water content is too little. This condition is termed water deficit. A value less than 275 mOsm/kg means there is too little solute for the amount of water or too much water for the amount of solute. This is termed water excess. Both conditions are clinically significant.
Isotonic
Fluids with the same osmolality as the cell interior are isotonic.
Hypotonic
Changes in the osmolality of ECF change the volume of cells. Solutions in which the solutes are less concentrated than in the cells are hypotonic (hypoosmolar).
Hypertonic
Fluids with solutes more concentrated than in cells, or an increased osmolality, are hypertonic (hyperosmolar). If hypertonic fluid surrounds a cell, water leaves the cell to dilute ECF. The cell shrinks and may eventually die.
Hydrostatic pressure
Hydrostatic pressure is the force of fluid in a compartment pushing against a cell membrane or vessel wall. In the blood vessels, hydrostatic pressure is the BP generated by the heart’s contraction.
Oncotic pressure
Oncotic pressure (colloidal osmotic pressure) is the osmotic pressure caused by plasma colloids (large molecules) in solution.
Plasma flow
As plasma flows through the capillary bed, 4 factors determine if fluid moves out of the capillary and into the interstitial space or if fluid moves back into the capillary from the interstitial space. The amount and direction of movement are determined by the interaction of (1) capillary hydrostatic pressure, (2) plasma oncotic pressure, (3) interstitial hydrostatic pressure, and (4) interstitial oncotic pressure.
Fluid spacing
Fluid spacing is a term used to describe the distribution of body water.
First spacing
First spacing describes the normal distribution of fluid in ICF and ECF compartments.
Second spacing
Second spacing refers to an abnormal accumulation of interstitial fluid (i.e., edema).
Third spacing
Third spacing occurs when excess fluid collects in the nonfunctional area between cells. This fluid is trapped where it is difficult or impossible for it to move back into the cells or blood vessels. Third spacing occurs with ascites; fluid leaking into the abdominal cavity with peritonitis or pancreatitis; and edema from burns, trauma, or sepsis.
Insensible water loss
Insensible water loss occurs with the invisible vaporization from the lungs and skin. It helps regulate body temperature.
Aldosterone
Aldosterone is a mineralocorticoid with strong sodium-retaining and potassium-excreting capabilities. Decreased renal perfusion or decreased sodium in the distal part of the renal tubule activates the renin-angiotensin-aldosterone system (RAAS), resulting in aldosterone secretion.
