Extracellular means
all of the fluid that resides outside the cells
Intracellular fluid means
Fluid inside the cell (most of the body is water resides inside cells)
What is transcellular fluid?
Miscellaneous extracellular fluid that includes cerebrospinal fluid, synovial fluid in the joints, vitreous and aqueous humors of the eye, and digestive secretions
If the concentration of electrolytes (therefore the osmolarity) of tissue fluid rises, water moves…
Out of the cells and into the tissues
If the osmolarity of tissue fluid falls, water moves…
Out of the tissues and into cells
What mainly determines the amount and direction of flow of fluid?
The concentration of solutes (particularly electrolytes) within each compartment
What is osmolarity?
The concentration of a solution expressed as the total number of solute particles per litre
What affects osmolarity?
Changes in water content, temperature and pressure
What are the mechanisms that increase fluid intake?
- Physical changes stimulate the thirst center in the hypothalamus.
- Salivation decreases, causing dry mouth and thirst.
- Water consumption occurs
What are the mechanisms to decrease output?
- Physical changes stimulate the hypothalamus.
- This stimulates the posterior pituitary to secrete antidiuretic hormone (ADH).
- ADH prompts the kidneys to reabsorb water and produce less urine.
- Fluid loss slows until water is ingested
What effect does antidiuretic hormone (ADH) have on the body?
Prompts the kidneys to reabsorb more water
Disorders of water balance can result from an abnormality in
Fluid volume
Fluid concentration
Distribution of fluid between compartments
When blood volume and pressure are too high, or blood osmolarity is too low, the hypothalamus inhibits the release of
ADH (This causes the renal tubule’s to reabsorb less water, leading to an increased urine output a decline in total body water)
Volume depletion results from
Blood loss or the loss of both water and sodium
Dehydration results when
The body eliminates more water than sodium
How do the kidneys usually compensate for excessive fluid intake?
By producing more urine
Fluid accumulation involves
The accumulation of fluid between compartments
Edema occurs when
Fluid accumulates in interstitial spaces, causing tissues to swell
What is the main electrolyte in extracellular fluid?
Sodium
What electrolyte determines the volume of total body water and influences how body water is distributed between fluid compartments?
Sodium
Sodium levels are primarily regulated by what 2 hormones? What do they adjust?
Aldosterone - Adjust the excretion of sodium
ADH - Adjust the excretion of water
If serum Na+ (water excess) is low, serum osmolarity is low, although strong prompts what To reabsorb Na+
Renal tubules
Once the renal tubule‘s reabsorb Na+ , What hormone release is suppressed, causing the kidneys to secrete more water?
ADH
Hypernatremia Refers to a plasma sodium concentration greater than 146 mEq/l. It usually indicates a
Water deficit
If and corrected, hypernatremia can cause
Edema, lethargy, and weakness
Hyponatremia refers to a plasma sodium concentration of less than 139 mEq/l. It usually results from
An excess of body water
Uncorrected, hyponatremia can result in
Pulmonary or cerebral edema as fluid moves into cells
What electrolyte is the chief cation of intracellular fluid?
Potassium
Hyperkalemia refers to a plasma concentration of K+ high. What effect does Hyperkalemia have on nerve and muscle cells?
Makes nerve and muscle cells irritable, leading to potentially fatal cardiac arrhythmias
Hypokalemia refers to a plasma concentration of K+ low. It results in
Muscle weakness, depressed reflexes, and cardiac arrhythmias
Besides strengthening bones, calcium plays a key role in what other 3 things?
Muscle contraction, nerve transmission, and blood clotting
Hypercalcemia inhibits
Depolarization of nerve and muscle cells
Hypocalcemia Increases…
Excitation of nerves and muscles
Why are electrolytes important?
Electrolytes allow the nervous system to conduct charges which the body needs to function properly
The pH of blood and tissue fluid ranges from
7.35 to 7.45
Chloride, the most abundant extracellular anion, is strongly linked to sodium. What is its role?
Contributes to the formation of stomach acid and also helps regulate fluid balance and pH
The pH of a solution is determined by
It’s concentration of hydrogen ions
