two compartments within the body that water occupies
Intracellular Fluid (ICF) Compartment
which actually consists of trillions of tiny individual “compartments”
Extracellular Fluid (ECF) Compartment
one-third or so of body water is outside cells
the fluid portion of blood
Interstitial Fluid (IF)
the fluid in the microscopic spaces between tissue cells.
have bonds (usually covalent bonds) that prevent them from dissociating in solution, and for this reason, no electrically charged species are created when nonelectrolytes dissolve in water
chemical compounds that do dissociate into ions in water. Because ions are charged particles, they can conduct an electrical current—and so have the name electrolyte.
Milliequivalents per liter (mEq/L)
a measure of the number of electrical charges in 1 liter of solution
water of oxidation, Body water produced by cellular metabolism.
Insensible Water Loss
Water that vaporizes out of the lungs in expired air or diffuses directly through the skin
is the driving force for water intake
Obligatory Water Losses
Output of certain amounts of water is unavoidable this helps to explain why we cannot survive for long without drinking.
Sensible water loss
of 500 ml in urine.
When water output exceeds intake over a period of time and the body is in negative fluid balance
when there is renal insufficiency or when an extraordinary amount of water is drunk very quickly, a type of cellular overhydration
low ECF Na_ concentration, which promotes net osmosis into the tissue cells, causing them to swell as they become abnormally hydrated
is an atypical accumulation of fluid in the interstitial space, leading to tissue (but not cell) swelling.
a condition of unusually low levels of plasma proteins, results in tissue edema because proteindeficient plasma has an abnormally low colloid osmotic pressure. Fluids are forced out of the capillary beds at the arterial ends by blood pressure as usual, but fail to return to the blood at the venous ends. As a result, the interstitial spaces become congested with fluid.
usually refers to the salt balance in the body
“has the most to say” about renal regulation of sodium ion concentrations in the ECF
appears to decrease Na reabsorption by blocking the effect aldosterone has on the renal tubules. Thus, progesterone has a diuretic-like effect and promotes Na and water loss.
such as cortisol and hydrocortisol, is to enhance tubular reabsorption of Na , but they also promote an increased glomerular filtration rate that may mask their effects on the tubules. However, when their plasma levels are high, the glucocorticoids exhibit potent aldosterone-like effects and promote edema.
in the heart and in the large vessels of the neck and thorax (carotid arteries and aorta) alert the cardiovascular centers in the brain stem. Shortly after, sympathetic nervous system impulses to the kidneys decline, allowing the afferent arterioles to dilate.
Parathyroid hormone (PTH)
Closely regulate ECF calcium ion levels
PTH activates bone-digesting osteoclasts, which break down the bone matrix, resulting in the release of Ca2+ and HPO4 2- to the blood.
PTH enhances intestinal absorption of Ca2+ indirectly by stimulating the kidneys to transform vitamin D to its active form, which is necessary for Ca2+ absorption by the small intestine.
PTH increases Ca2+ reabsorption by the renal tubules while decreasing phosphate ion reabsorption. In this way, calcium conservation and phosphate excretion go hand in hand. The product of Ca2+ and HPO4 2- concentrations in the ECF remains constant, preventing calciumsalt deposits in bones or soft body tissues.
pH of arterial blood rises above 7.45
drop in arterial pH to below 7.35 results
a system of one or more compounds that acts to resist changes in pH when a strong acid or base is added.
Bicarbonate Buffer System
a mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3, a weak base), in the same solution. Although it also buffers the ICF, it is the only important ECF buffer.
all the available HCO3- ions
Phosphate Buffer System
nearly identical to that of the bicarbonate buffer. The components of the phosphate system are the sodium salts of dihydrogen phosphate (H2PO4 -) and monohydrogen phosphate (HPO4 2-).NaH2PO4 acts as a weak acid.Na2HPO4,with one less hydrogen atom, acts as a weak base.
Protein Buffer System
Proteins in plasma and in cells are the body’s most plentiful and powerful source of buffer.
Metabolic (fixed) Acids
acids generated by cellular metabolism: phosphoric, uric, and lactic acids, and ketone bodies.
the most common cause of acid-base imbalance. It most often occurs when a person breathes shallowly or when gas exchange is hampered by diseases such as pneumonia, cystic fibrosis, or emphysema. Under such conditions, CO2 accumulates in the blood. Thus, respiratory acidosis is characterized by falling blood pH and rising PCO2
results when carbon dioxide is eliminated from the body faster than it is produced. This is called hyperventilation, and results in the blood becoming more alkaline
is recognized by low blood pH and HCO3- levels, The second most common cause of acid-base imbalance
indicated by rising blood pH and HCO3- levels, is much less common than metabolic acidosis
As a rule, changes in respiratory rate and depth are evident when the respiratory system is attempting to compensate for metabolic acid-base imbalances.
When an acid-base imbalance is of respiratory origin, renal mechanisms are stepped up to compensate for the imbalance.