11 Volume Regulation Flashcards
What does the kidney use to measure body volume?
effective circulating volume
When might effective ciculating volume and actual volume change independently?
heart failure
What is the structure of the juxtaglomerular apparatus?
the late distal tube comes into contact with the afferent arteriole
What secretes renin?
granular cells of the afferent arteriole
What is the thickening in the distal tubule called?
macula densa
What does the macula densa detect?
low Na+ in the distal tubule
What do juxtaglomerular cells do?
release renin
What does renin do?
converts angiotensinogen into angiotensin 1
Where is angiotensinogen formed?
liver
adipose tissues
What happens to angiotensin 1?
converted to angiotensin II by angiotensin converting enzyme (ACE) in the lungs
What does angiotensin II do?
efferent arteriole vasocontristion
stimulates aldosterone release
increases sodium reabsorption
What are the 2 main triggers for aldsoterone?
ATII
Hyperkalaemia
What does aldosterone do in the collecting ducts?
reabsorbs sodium, and drives potassium excretion
What broad effect does inhibiting the renin angiotensin system do?
reduces blood pressure, acting as an antihypertensive
Name 4 types of antihypertensives associated with the renin angiotensin system
ACE inhibitors
AT(1) receptor antagonists
aldosterone receptor antagonsits
renin inhibition
Name 2 types of ACE inhibitors?
captopril
enalopril
What is the problem with using ACE inhibitors?
How is this avoided?
ACE has other functions, like breaking down bradykinin, an inflammatory marker
people hence get a dry cough
we just put them on something else lol, that acts downstream of ATII
What is the familial pharmaceutical name for AT(1) receptor antagonists?
sartans
What is the agonist for AT(1)?
ATII
Name a type of aldosterone receptor antagonist
spironolactone
Name a type of renin inhibitor
aliskiren
what do AT(1) receptors do?
Gq linked so vasoconstriction in efferent arteriole
How does angiotensin II increase circulating volume?
increases Na / H+ exhcnage in proximal tubule and hence proximal Na+ absorption
increase in aldosterone release
causes ADH release
causes thirst
How does Haemorrhage lead to increased renin release
…. decreased circulating volume, decreasing blood pressure and increasing sympathetic activity
sympathetics act on granule cells
What are the 3 key sympathetic effects on the afferent arteriole?
vasoconstriction upstream of granule cells (amplifies apparent fall in volume)
direct stimulation of renin release from granule cells
afferent arteriole vasoconstriction to lower GFR
What does noradrenaline binding to alpha 1 adrenoreceptors cause?
vasoconstriction
what does noradrenaline binding to beta 1 adrenoreceptors cause?
why is this unusual?
on granule cells to regulate renin release
these receptors are usually found in the heart!
What are the 3 key stimuli to renin release?
intrinsic renal mechanisms because of less Na+
sympathetic mediated release
decrease in venous pressure
How does decreasing venous pressure stimulate renin release?
it is transmitted to vesa recta capillaries, decreasing hydrostatic pressure
this increases uptake of fluid from renal interstitial space, increasing water reabsorption
this decreases sodium delivery to the distal tubules
what stimulates ADH release?
change in osmolality
change in volume a lil bit
how does changing volume affect ADH?
decreased cardiac output, decreased activation of baroreceptor reflex
AtII increases ADH release following haemorrhage (increases water reabsorption, lowering osmolality, this mechanism does not retain Na+)
What will the acute response to haemorrhage be?
hyponatraemia
Why does beer cause diuresis?
it increases water load and also inhibits ADH
Why do spirits dehyrdrate you?
you aren’t really taking in enough water to facilitate that loss
What is ANP and what does it do?
Atrial Natriuretic Peptide
atrial stretch in volume overload cuases its’ release
travels to the kidney acting on ANP receptors increasing cGMP
this increases renal Na+ excretion
Name a peptide similar to ANP produced in the kidney
Urodilatin
What do prostaglandins do?
PGE2 and PGI2 increase Na+ excretion
Why do we have to watch out when giving renally compromised people NSAID’s?
they have problems with volume retention anyway, and NSAID’s tend to be nephrotoxic on top of this
What does dopamine do?
angonist to D1 receptors, increasing cAMP, decreasing activity of Na+ / H+ exchanger in the proximal tubule
this increases Na+ excretion
