Fluid and elcetrolyte
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73 Terms
what is the main intracellular ion
potassium
what is the main extracellular ion
sodium
where is the majority of the work of the kidney undertaken
in the cortex of the nephrons
what is glomerular filtration rate controlled by
blood flow
intraglomerular pressure
transmembrane pressure
oncotic pressure
what components make up the control of blood flow in glomerular filtration rate
angiotensin II
myogenic control
SNS
baroreceptor
what does SNS cause to control blood flow in GFR
direct vasocontriction
what will occur in the instance of reduced blood flow
baroreceptor – SNS / renin – ADH / AgII – increased sodium reabsorption ‘distal sensing’
what are the two ways in which the kidney control fluid and electrolytes
tubular reabsorption and tubular secretion
how does tubular reabsorption control fluid and electrolytes
active via channels
passive down concentration or osmotic gradients
what % of filtrate is reabsorbed
99%
how is excretion calculated
excretion = (filtration - reabsorption) + secretion
normal concentration of solutes in plasma
285-295mosmol/kg
what % of reabsorption occurs in the PCT
70%
what will follow sodium in PCT
almost everything
what hormone is involved in the PCT
only really angiotensin II which partially controls sodium
how long is the proximal convoluted tubule
14mm
what are the loop rules
Thick ascending limb is impermeable to water, but actively transports sodium, potassium and chloride
Thick ascending limb provides the concentration gradient to promote water reabsorption from the thin DLH
Thin descending limb is freely permeable to salt and water
Vasa recta doesn’t wash away the gradient by using countercurrent exchange
what is the thick ascending limb impermeable and permeable to
impermeable to water
permeable to sodium, potassium and chloride
what does the thick ascending limb provide
the concentration gradient for water to be reabsorbed are the thin DLH
what is the thin descending limb permeable to
salt and water
what does the vasa recta NOT do
it will not wash away the gradient by using countercurrent exchange
where does osmotic equilibrium occur
in the thin descending limb
where is NaCl reabsorbed
in the water permeable ascending limb
what does reabsorption of water in the thin ascending limb cause
a hypotonic fluid which will pass to the distal tubule
what are the vasa recta capillary walls
highly permeable
how is dissipation of the medullary osmotic gradient minimised
due to the U shaped arrangement of the vessels in the vasa recta
what channel is responsible for NaCl movement in the thick ascending limb
NKCC2
how long is the distal convoluted tubule
1mm
what channel is responsible for the movement of NaCl in the distal tubule
NCC
what hormone is used to regulate action of the collecting duct
antidiuretic hormone
what will antidiuretic hormone cause
it will cause aquaporins to be inserted into the membrane which will allow for the movement of water
what will trigger the synthesis of ADH in the hypothalamus
serum osmolarity high
decreased stretch detected by baroreceptors
decreased stretch in the atrial receptors
what will hypothalamus synthesis of ADH cause
thirst
direct vasoconstriction
ADH will go to the posterior pituitary where it can be released from
what does release of ADH from the posterior pituitary cause
it will cause aquaporins to be inserted into the membrane which will allow for water movement
what does thirst, vasocontriction and water reabsorption cause
intravascular volume maintenance
what receptor will ADH act on for aquaporins action
V2 receptors which will cause cAMP release, cAMP will cause vesicles containing aquaporin to be fused with the membrane
what channel is responsible for sodium reabsorption in the collecting duct
ENaC
what channels are found in the PCT
NaK ATPase, Na/H antiporter
SGLT2
what channel is found in the thick ascending loop
NKCC2
what channel is found in the DCT
NCC
what channels are found in the collecting duct
ENaC
aquaporins
what is SGLT2
sodium dependant glucose co transporter
what % of glucose is reabsorbed at the PCT by SGLT2
98%
what happens to transporters when there is high amount of filtered glucose
it will cause the co transporter to be saturated and glucose is excreted in the urine
where do SGLT2i work
on SGLT2 in the PCT
where do loop diuretics work
on NKCC2 in thick ascending limb
where do thiazide diuretics work
on NCC in the DCT
where do K sparing diuretics work
on ENaC in collecting duct
give an example of PCT inhibitor
acetazolamide
give an example of NKCC2 inhibitor
loop
give an example of NCC inhibitor
thiazide
give an example of ENaC inhibitor
amiloride
what are the main measured waste products
urea and creatinine
what may high urea and creatinine levels attribute to
uraemic syndrome
what is urea
a breakdown product of amino acid metabolism in the liver
where is urea reabsorbed
in the collecting duct
what is urea involved in
the countercurrent exchange and maintaining concentration gradient
what is creatinine
a breakdown product of muscle - creatinine phosphate
where is creatinine freely filtered
glomerulus
what is the tubular secretion of creatinine
minimal
what are the urinary electrolytes
sodium, potassium, calcium and chloride
what may high urinary chloride suggest
suspected diuretic abuse
what is urinary calcium used to differentiate
between Bartters and Gitelmans
what is urinary sodium used to assess cause of
hyponatraemia
what is induced natiuresis
caused by diuretics
osmolarity and volume of maximum urine output
12L and 50mosmol
osmolarity and volume of minimum urine output
0.5L at 1400mosmol
what mosmol of waste is excreted per day
600mosmol
how much ml is filtered by glomeruli per minute
100ml
what is reabsorbed proximally after glomerulus has filtered plasma
sodium, glucose water and amino acids
what happens to waste products after plasma has been filtered by the glomerulus
they will concentrate the urine, this is urea and creatinine
what happens to Na and water in the distal nephron
fine tuning which is regulated by aldosterone and angiotensin II
what % of filtrate is reabsorbed and excreted
99% reabsorbed
1% excreted