Renal 5 Flashcards
why do we focus on 4 variables
body is in constant flux
- ingest 2l of fluid containing 6-15g NaCl
- take in varying ions
what is mass balance for fluid and electrolyte balance
whatever comes in must be excreted if not needed
how are fluids and electrolytes excreted
kidneys are primary route, small amounts in feces and sweat, lungs lose water and help remove H+, HCO3 by excreting CO2
why are we concerned with homeostasis fo H20 and Na
determine ECF and osmolarity
why are we concerned with K+ balance
can cause problems with cardiac and muscle function
why are we concerned with Ca2+
involved in many processes in body
why are we concerned with H+ and HCO3
determine body pH
why is maintaining osmolarity in the body important
water can cross most cell membranes freely
- can affect cell volume and most cells do not have mechanisms
what cells have independent mechanisms for maintaining cell volume
renal tubule cells
liver cells
how is fluid and electrolyte balance an integrative process
involves the respiratory, cardiovascular and renal systems as well as behavioural responses
what controls cardiovascular and respiratory systems
neural control and are rapid
what controls renal responses
endocrine and neuroendocrine control
slower
what can CV and resp. systems do before renal response
can kick in for temporary fix but renal will completely fix
- pathways overlap
what triggers homeostatic reflexes
volume receptors in atria and carotid and aortic baroreceptors respond to change in volume or bp
if decrease in blood volume and BP what does CV system do
increase cardiac output and vasoconstriction to increase BP
If decrease in blood volume and BP what does Behaviour response do
increases thirst which increase ECF and ICF volume and increases BP
if decrease in blood volume and BP what do kidneys do
conserve salt and water to minimize further volume loss
if increase blood volume and BP what does CV system do
decrease cardiac output and vasodilation to decrease BP
if increase in blood volume and BP what does kidneys do
excrete salts and H2O in urine, decreases ECF and ICF volume which decreases BP
water makes up how much of body weight
50-60%
water intake must match what
excretion
how much water in ICF
2/3
how much water in ECF
1/3
Plasma (25%)
interstitial fluid (75%)
what kind of mechanism is water loss in urine under normal conditions
regulated
how is water gained
food and drink, metabolism
how is water lost
skin, lungs, urine, feces
what can the kidneys not do
can remove excess and conserve fluid but cannot replace what is lost
what does volume loss result in
reduced GFR, volume loss in urine is reduced, reabsorption can be increased
what must volume loss be replaced through
behavioural mechanisms
what creates concentrated urine
renal medulla
what is the osmolarity of urine a measure of
how much water is excreted by kidneys
when removal of excess water is required what happens
kidneys produced large volume of dilute urine
- as low as 50mOsM
if kidneys need to conserve water what do they do
low volume of concentrated urine
- up to 1200mOsM
how do the kidneys control urine concentration
vary amounts of water and Na reabsorbed in distal nephron (distal tubule and collecting duct)
how do kidneys produced dilute urine
distal nephron must reabsorb solute without allowing water to follow by osmosis (regulated aquaporins)
how do kidneys produces concentrated urine
distal nephron must reabsorb water and little solute
what happens in proximal tubule
only water reabsorbed (interstitial has lot of solute)
what is osmolarity as further and further down medulla
more and more concentrated
how do distal tubule and collecting duct alter their permeability to water
adding and removing water pore in apical membrane
what are the aquaporins under direction of
posterior piuitary hormone vasopressin (AVP)
what is another word for vasopressin
antidiuretic hormone (ADH)
with max vasopressin what occurs
collecting duct is freely permeable
- water leaves carried away by vasa recta
- urine is concentrated
what happens with absence of vasopressin
collecting duct is impermeable to water and urine is dilute
- large volume urine and no rebsorption
what is insertion of AQP2
graded, depends on amount of AVP
what stimulates vasopressin secretion
blood volume, pressure, and osmolarity (most potent)
How does circadian rythm affect AVP
at night it is increased, prevents peeing, increased reabsorption of H20
what is osmolarity monitored by
osmoreceptor neurons
what is low blood volume sensed by
atrial stretch receptors
what is decreased BP sensed by
carotid and aortic baroreceptors
what produces and releases AVP
magnocellular neurosecretory cells (MNC’s)
what are osmoreceptors
stretch sensitive neurons that increase firing rate as osmolarity increases
what do the osmoreceptors signal to
to MNC’s where APs fire causing release of AVP containing vesicles
what else signals to MNC’s
baro and atrial receptors
where are vesicles containing AVP stores
posterior pituitary
what is the countercurrent multiplier
the loop of henle
what is necessary to create the concentration gradient for osmotic movement of water out of collecting duct
high osmolarity within the medullary interstitum
what created hyperosmotic interstitium
countercurrent exchange systems
urea
what is the countercurrent exchange system
loop of henle and vasa recta run in opposite directions and loop of henle close together
