Controlling Movement

Question 1

ECF main cations

Answer 1

Mainly sodium with small amounts of potassium, calcium and magnesium

Question 2

ECF main anions

Answer 2

Mainly chloride, with small amounts of bicarbonate, sulfate, and phosphate anions

Question 3

ICF main cations

Answer 3

The main cation is potassium, with small amounts of magnesium and sodium.

Question 4

ICF main anions

Answer 4

The main ICF anion is phosphate, with some protein and a small amount of bicarbonate.

Question 5

Cations

Answer 5

Cations are positively charged ions. Examples include sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) ions

Question 6

Anions

Answer 6

Anions are negatively charged ions. Examples include bicarbonate ( ), chloride (Cl − ), and phosphate ( ) ions. Most proteins bear a negative charge and thus are anions.

Question 7

Electrolytes

Answer 7

Electrolytes are substances whose molecules dissociate, or split, into ions when placed in water. Electrolyte composition varies between ECF and ICF.

Question 8

Ions

Answer 8

Ions are electrically charged particles

Question 9

Diffusion

Answer 9

Diffusion is the movement of molecules from an area of high concentration to low concentration

Question 10

Facilitated diffusion

Answer 10

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.

Question 11

Active transport

Answer 11

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.

Question 12

Osmosis

Answer 12

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.

Question 13

Osmolality

Answer 13

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.

Question 14

Plasma osmolality

Answer 14

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.

Question 15

Isotonic

Answer 15

Fluids with the same osmolality as the cell interior are isotonic.

Question 16

Hypotonic

Answer 16

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).

Question 17

Hypertonic

Answer 17

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.

Question 18

Hydrostatic pressure

Answer 18

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.

Question 19

Oncotic pressure

Answer 19

Oncotic pressure (colloidal osmotic pressure) is the osmotic pressure caused by plasma colloids (large molecules) in solution.

Question 20

Plasma flow

Answer 20

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.

Question 21

Fluid spacing

Answer 21

Fluid spacing is a term used to describe the distribution of body water.

Question 22

First spacing

Answer 22

First spacing describes the normal distribution of fluid in ICF and ECF compartments.

Question 23

Second spacing

Answer 23

Second spacing refers to an abnormal accumulation of interstitial fluid (i.e., edema).

Question 24

Third spacing

Answer 24

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.

Question 25

Insensible water loss

Answer 25

Insensible water loss occurs with the invisible vaporization from the lungs and skin. It helps regulate body temperature.

Question 26

Aldosterone

Answer 26

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.