4 Body Fluids Flashcards
Solutes in the body fluid compartments create what?
osmotic pressure
What hormone directly controls water homeostasis?
ADH- vasopressin
T-F– there is osmotic and non-osmotic control of ADH release?
True
Disorders of water homeostasis or disorders of osmoregulation are disorders of the serum _____concentration?
Na
What is the total body water percentage in males? in females?
60% and 50% of body weight
What is the intracellular fluid vs. extracellular fluid total body water?
60% of TBW and 40% of TBW
What is the breakdown of extracellular fluid into percentages with regards to interstitial fluid, plasma, and trancellular?
75%, 20%, 5% of ECF
Is Na or K largely intracellular?
K…Na is extracellular
What is the typical volume of liters in men of water?
42
What is it called when extracellular fluid is shifting to intercellular? about how much at any given time?
trancellular—1 liter
Movement of ions across cell membranes is dependent on what?
transport proteins
What is the most abundant cation in the ECF?
Na—[major determinant of the osmolarity of ECF Posm= 2Na+Glu/18+BUN/2.8=280-290 mosm/kg]
what is the hydrostatic pressure produced by a difference in concentration between solutions on the two sides of a surface?
osmotic pressure
T-F–osmotic pressure is proportional to the size, weight and valence of solute particles?
False–only to the number of particles
What determines the distribution of water in body fluid compartments?
osmotic pressure
What is a homeostatic mech of organisms to reach balance in osmotic pressure?
osmoregulation
What prevents the body fluids from becoming too dilute or too concentrated?
osmoregulation
T-F the ICF and ECF compartments are generally not in osmotic equilibrium?
False- they are
What is the effect of a solution on the volume of a given cell?
tonicity
T-F– all substances create an osmotic pressure?
False- substances that cross cell membranes do not create osmotic pressure
Is urea an ineffective osmole?
yes
What are the three different types of tonicities in solution?
isotonic
hypotonic [water flows into cell]
hypertonic [water flows out of cell]
What is the normal intake of water / day?
1200 ml
Does water intakes only include oral intake?
No- also that generated by cell metabolism [also maybe an IV in a hospitalized patient]
Besides renal excretion–how else can water leave the body?
respiration in lungs and evaporation in the skin– these are known as insensible water loss [also feces—amount increases in diarrhea]
is skin, sweat and exhaled air easy to measure in regards to water loss?
No- need formulas to estimate
Where is ADH synthesized?
hypothalamus-supraoptic and paraventricular nuclei of hypothalamus
Where do the secretory granules of ADH travel down axons to?
neurohypophysis
What is the site of action of ADH?
cortical (and medullary) collecting tubule and duct
What is diuresis? antidiuresis?
- large volume of urine [dilute]
- small volume of urine [concentrate]
What is a separate group of cells located in proximity to thirst center and to supraoptic and paraventricular nuclei main function?
Osmoreceptors- sensitive to as little as 1% change in Posm
What is the set point for release of ADH?
280 mOSm/Kg H2O
what are non-osmotic receptors that function to maintain water homeostatis?
baroreceptors
Where are the low-pressure baro-receptors?
Left atrium, lung vasculature
Where are the high pressure baroreceptors?
carotid sinus and aortic arch
What fibers carry baroreceptor information?
Vagus an Glossopharyngeal nerves.
Is sensitivity for baroreceptors higher or lower than that for osmolality?
lower
Why would sensitivity for baroreceptors be lower than that for osmolality?
need to maintain circulating volume supersedes that of osmolality
T-f— the volume stimulus for ADH supersedes the osmotic stimulus?
TRUE
T-F– water is unable to freely move across all body fluid compartments?
False- can freely move
