A&P 26: Fluid, Electrolyte, & Acid-Base Balance Flashcards
Fluid compartments
water occupies 2 main ___ ______ within the body
Intracellular fluid compartment (ICF)
almost 2/3 by volume of the water in the body is in this compartment
Extracellular fluid compartment (ECF)
1/3 of the water in the body is in this compartment
Plasma
fluid portion of the blood
Interstitial Fluid (IF)
fluid in the microscopic spaces between tissue cells
Nonelectrolytes
substances that have bonds (usually covalent) that prevent them from dissociating in solution
Electrolytes
chemical compounds that do dissociate into ions in water
Milliequivalents per liter (mEq/L)
measure of the electrical charges in 1 L of solution
Metabolic water (water of oxidation)
body water produced by cellular metabolism
Insensible water loss
water that vaporizes out of the lungs in expired air or that diffuses directly through the skin
Thirst mechanism
driving force for water intake
Obligatory water losses
output of certain amounts of water is unavoidable; helps to explain why we can’t survive for long without drinking
Sensible water loss
minimum daily water loss of 500mL in urine
Dehydration
fluid loss, either the loss of water or the loss of water and solutes together
Hypotonic hydration
cellular overhydration
Hyponatremia
hallmark of hypotonic hydration; low ECF Na+ concentration; promotes net osmosis into tissue cells, causing them to swell as they become abnormally hydrated
Edema
atypical accumulation of fluid in the interstitial space, leading to tissue (but not cell) swelling
Hypoproteinemia
condition of unusually low levels of plasma proteins; results in tissue edema because protein-deficient plasma has abnormally low colloid osmotic pressure
Electrolyte balance
salt balance in the body
Aldosterone
hormone that “has the most to say” about renal regulation of sodium ions
Atrial natriuretic peptide (ANP)
reduces blood pressure and blood volume by inhibiting nearly all events that promote vasoconstriction and Na+ and water retention
Estrogens
chemically similar to aldosterone; like aldosterone, enhance NaCl reabsorption by the renal tubules; female sex hormone; responsible for water retention when its levels rise during the menstrual cycle and the edema during pregnancy
Progesterone
decreases Na+ reabsorption by blocking the effect aldosterone has on the renal tubules; diuretic-like effect; promotes Na+ and water loss
Glucocorticoids
cortisol and hydrocortisol; enhance tubular reabsorption of Na+ ; promote an increase glomerular filtration rate that may mask their effect on the tubules
Parathyroid hormone (PTH)
ECF calcium ion levels are closely regulated by this hormone
Acid-base balance
nearly all biochemical reactions are influenced by the pH of their fluid environment; closely regulated
Alkalosis
whenever the pH of arterial blood rises above 7.45; AKA alkalemia
Acidosis
a drop in arterial pH below 7.35 results in this condition; AKA acidemia
Chemical buffer
system of 1 or more compounds that resists changes in pH when a strong acid or base is added; binds to H+ when pH drops and releases them when pH rises
Bicarbonate buffer system
mixture of carbonic acid and its salt, sodium bicarbonate, in the same solution; buffers the ICF, but is the ONLY important ECF buffer
Alkaline reserve
if enough acid enters the blood so that all available HCO3- ions, referred to as __ ___, are tied up, the buffer system becomes ineffective and blood pH changes
Phosphate buffer system
operation of this system is nearly identical to that of the bicarbonate buffer; components = sodium salts of dihydrogen phosphate and monohydrogen phosphate
Protein buffer system
proteins in plasma and in cells are the body’s __ ___ ___; 3/4 of all the buffering power of body fluid resides and cells & most of this reflects the powerful buffering activity of intracellular proteins
Amphoteric molecules
molecules that can function reversibly as either an acid or base depending on the pH of its environment
Volatile acid
an acid that can be eliminated by the lungs; carbonic acid is converted to CO2, which diffuses into the alveoli
Nonvolatile (fixed) acids
acid generated by cellular metabolism that must be eliminated by the kidneys
Respiratory acidosis
common cause of acid-base imbalance; most often occurs when a person breathes shallowly or when gas exchange is hampered by diseases such as pneumonia, cystic fibrosis, or emphysema
Respiratory alkalosis
results when CO2 is eliminated from the body faster than it is produced; AKA hyperventilation; results in the blood becoming more alkaline; often due to stress or pain
Metabolic acidosis
2nd most common cause of acid-base imbalance; recognized by low blood pH and HCO3- levels; typical causes = ingesting too much alcohol (metabolized to acetic acid), excessive loss of HCO3- (persistent diarrhea), accumulation of lactic acid during exercise or shock, ketosis in diabetic crisis/starvation, kidney failure (infrequent)
Metabolic alkalosis
indicated by rising blood pH and HCO3- levels; much less common than its opposite; typical causes = vomiting the acidic contents of the stomach (or loss of those secretions through GI suctioning), intake of excess base (too many antacids)
Respiratory and renal compensations
the respiratory system attempts to compensate for metabolic acid-based imbalances, and the kidneys (though much slower) work to correct imbalances caused by respiratory disease; recognized by resulting changes in plasma Pco2 and bicarbonate ion concentrations
