Chr. 27 - Fluid, Electrolyte, and Acid-Base Homeostasis Flashcards
[27.1] What is a body fluid?
A substance produced by the body consisting of water and dissolved solutes.
Two main types: intracellular fluid and extracellular fluid.
[27.1] What is intracellular fluid?
Fluid with the cell.
[27.1] What is extracellular fluid?
Fluid existing outside cells.
[27.1] What is interstitial fluid?
Extracellular fluid existing in the microscopic spaces between tissue cells. 80% of extracellular fluid.
[27.1] What is blood plasma?
Extracellular fluid composing the liquid portion of blood. 20% of extracellular fluid.
[27.1] What is fluid balance?
The required amount of water and solutes correctly proportioned among the various compartments.
[27.1] What is the largest signle component of the body?
Water, 45-75% of total mass.
[27.1] What is an electrolyte?
Inorganic compounds that dissociate into ions when dissolved. Affects fluid balance through osmosis.
[27.1] What is metabolic water?
Water produced in the body when electrons are accepted by oxygen during aerobic respiration. 200mL/day
[27.1] What is the thirst center?
An area of the hypothalamus governing the urge to drink.
[27.1] What is dehydration?
A decrease in water volume and increase in osmolarity of body fluids.
[27.1] What are osmoreceptors?
Receptors in the hypothalamus that detect increased blood osmolarity and stimulate the thirst center.
[27.1] What receptors stimulate the thirst center?
Water BANS:
1. Baroreceptors in blood vessels
2. Angiotensin II
3. Neurons within the mouth detecting dryness.
4. Stretch receptors in the atria
[27.1] How does elimination of excess body water occur?
Mainly by control of urine output.
[27.1] What is the main factor of urine output determining body fluid volume?
Urinary salt loss.
[27.1] What is the main hormone regulating water loss?
Antidiuretic hormone.
[27.1] Which other hormones play a role in fluid balance?
Aldosterone and atrial natriuretic peptide.
[27.1] How does aldosterone play a role in fluid balance?
Promotes reabsorption of sodium in the distal convoluted tubule and collecting ducts. Water follows the sodium, increasing blood volume.
[27.1] How does atrial natriuretic peptide play a role in fluid balance?
Promotes natriuresis, elevated excretion of sodium into urine leading to increase water loss.
[27.1] What is hypertonicity of extracellular fluid?
When solutes occur in greater concentration within extracellular fluid, drawing out fluid from within cells and causing them to shrink.
[27.1] What is hypotonicity of extracellular fluid?
When solutes within a cell occur at greater concentration than extracellular fluid, leading to movement of water into cells and causing swelling.
[27.1] What is water intoxication?
A state in which excessive body water causes cells to swell dangerously, occurs when water intake occurs faster than kidneys can excrete it.
[27.2] List the four general functions of ions within the body.
- Control osmosis of water between compartments
- Maintain acid-base balance
- Carry electrical current
- Serve as cofactors for enzymes.
[27.2] What is milliequivalents per liter (mEq/liter)?
The unit of measurement expressing the concentration of ions. Typically 1mmol/liter for ions with a single charge, and 2mmol/liter for ions with two charges, positive or negative.
[27.2] What is an equivalent?
A positive or negative charge equal to the charge of one mole of hydrogen; 1g of hydrogen.
[27.2] What is a milliequivalent?
One one-thousandth of an equivalent.
[27.2] What is the most abundant ion in extracellular fluid?
Sodium, most abundant ion, and most abundant positive ion.
136 - 148 mEq/liter in blood plasma.
[27.2] What is hyponatremia?
Blood plasma concentration of sodium below 135 mEq
[27.2] What is hypernatremia?
Blood plasma concentration of sodium above 148 mEq
[27.2] What is the most abundant negative ion in extracellular fluid?
Chloride.
95 - 105 mEq in blood plasma.
[27.2] What is the most abundant cation in intracellular fluid?
Potassium
3.5 - 5 mEq in blood plasma.
[27.2] Why does the mEq/liter of bicarbonate fluxuate?
As blood absorbs carbon dioxide from cellular metabolic waste, it combines with water in the blood plasma to form bicarbonate.
22 - 26 mEq in arterial blood plasma
23 - 27 mEq in venous blood plasma
[27.2] What is the most abundant mineral in the body?
Calcium.
4.5 - 5.5 mEq in blood plasma.
[27.2] Describe the presence of phosphate in the body.
Occurs as calcium phosphate salts in bones and teeth, as phosphate ions ((H2PO4)-, (HPO4)2-, and (PO4)3-) acting as intracellular anions and a buffer for hydrogen ions.
1.7 - 2.6 mEq in blood plasma.
[27.2] What hormones regulate calcium and phosphate levels?
Parathyroid hormone and calcitriol.
[27.2] Describe the presence of magnesium in the body.
Occurs as magnesium salts forming bone, as well as intracellular cations. Also acts as a cofactor for enzymes.
1.3 - 2.1 mEq in blood plasma.
[27.3] List the major mechanisms for removal of hydrogen ions from body fluids.
- Buffer systems
- Exhalation of carbon dioxide
- Kidney excretion of hydrogen
[27.3] What is a buffer system?
A mechanism composed of a weak acid and a weak base, typically a salt formed from the acid. Prevents rapid, drastic changes of pH by converting strong acids and bases to weaker ones.
[27.3] Describe the protein buffer system.
A prolific buffer system between intracellular fluid and blood plasma utilizing the carboxyl and amino groups of amino acids, as well as side chains of 7/20 amino acids. Able to buffer acids and bases.
[27.3] Describe the carbonic acid - bicarbonate buffer system.
A buffer system utilizing bicarbonate as a weak base and carbonic acid as a weak acid. Carbonic acid provides flexibility, removing excess hydrogen and dissociating into water and carbon dioxide, or release hydrogen ions and forming bicarbonate.
[27.3]
