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Flashcards in Sodium and Water Balance Deck (18)
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what hormone controls water balance and where is it secreted from

ADH(anti-diuretic hormone), secreted from posterior pituitary


what class of hormones controls sodium balance and where is it secreted from

Steroids, secreted from adrenal glands


describe the action of ADH

causes water reabsorption from the renal tubules, makes you pee less


what affect does increased and decreased ADH have on urine

increased ADH = small volume conc. urine
decreased ADH = large volume dilute urine


describe what urine osmolality is

a measure of the urine conc./dilution


describe high and low osmolality in terms of urine

high osmolality = concentrated urine
low osmolality = dilute urine


what is the effect of steroids on Na balance called and what does it refer to

mineralocorticoid activity, refers to Na reabsorption in renal tubules in exchange for K+/H+


give 2 examples of steroids with mineralocorticoid activity

aldosterone(main one) and cortisol


what affect does too much and too little mineralocorticoid have on the sodium balance

too much = sodium gain
too little = sodium loss


what is the equation to calculate Na conc.

(mmol Na) / (1L H2O)


what does hyponatraemia and hypernatraemia mean

hyponatraemia = low [Na]
hypernatraemia = high [Na]


in terms of water and sodium what are the two ways in which hyponatraemia can occur

Na is too low
or H20 is too high


in terms of water and sodium what are the two ways in which hypernatraemia can occur

Na is too high
or H20 is too low


what is the [Na] in extracellular fluid compared to intracellular fluid

extracellular = 140 mmol/L
intracellular = 4mmol/L


water is present in all body compartments, what does this mean in terms of water gain and loss

when water is lost or gained it is lost and gained from all tissues equally, not more in different compartments


what compartment is sodium confined to and by what, and what does this mean for sodium loss/gain

confined to extracellular fluid(ECF), by Na/K ATP pump
so Na loss/gain is only in ECF


considering water moves by osmosis describe how Na affects water movement

[Na] is vastly greater than anything else, so water follows Na
ie if you lose/gain Na, you lose/gain water


when you lose/gain water due to sodium loss or gain, where is that water lost/added from/to

lost or added from/to the ECF, as that is where the sodium is confined to and lost/added from/to, and water follows sodium
(results in significant water gain/loss due to smaller volume of ECF)