control of blood pressure: role of the kidney Flashcards
what is blood (basic)
comprises red blood cells and plasma
what is the influence of blood on the kidneys
red blood cell mass is altered by erythropoietin
plasma volume is altered by salt excretion by RAAS, anti-diuretic hormone (ADH) and atrial natriuretic peptide (ANP)
the state of circulation is communicated to the kidneys by hormones and pressure natriuesis
influence of hormones on blood
hormones which control water excretion and renal salts are influences by cardiovascular receptors and intitiates hormonal control
Renin-Angiotensin-aldosterone systemw
what is the hormonal control delivered by RAAS
decreased renal perfusion pressure, a decrease in effective circulating volume = decreased stretch on afferent arterioles which increases renin
rise in sympathetic nervous system activity to kidneys
decreased NaCl concentration in the macula densa
3 main mechanisms independently or in combination to stimulate renin production
what is renin
produced by juxtaglomerular cells
cleaves angiotensinogen to angiotensin I
proteolytic
how does RAAS increase blood pressure
- stimulation of aldosterone so more water is absorbed
- stimulation of generalised vasoconstriction
- stimulation of thirst
what is angiotensin II
a vasoconstrictor peptide
produced after a fall in BP
how is angiotensin II produced
stimulated by secretion of renin
stored in afferent arterioles of the kidney
produced by conversion from angiotensin I by angiotensin converting enzymes (ACE) in the lung
what is the influence of angiotensin II on aldosterone
stimulates aldosterone from the adrenal cortex
aldosterone stimulates Na+ reabsorption
requires; Na+/K+ pump insertion on basal membrane and Na+ channel on apical membrane
increase in Na+ reabsorption leads to an increase in H2O absorbance via osmosis
stimulation of osmosis which contributes to maintenance of plasma volume and blood pressure
what is the contribution of angiotensin II in vasoconstriction
binds to At1 receptor on vascular cells
stimulates contraction and therefore vasoconstriction
contributes to changes in total peripheral resistance
what is the contribution of angiotensin II on the sympathetic nervous system
increases sympathetic outflow directly in the brain - stimulates sympathetic nervous system action potential generation
what causes the release of renin
- hypotension > juxtaglomerular cells in arterioles inhibited by stretch, fall in blood pressure causes release
- increased renal sympathetic nervous system activity > stimulates renin secretion by activation of adrenergic receptros
- a fall in NaCl concentration > activates cascaded starting from macula densa
RAAS summary
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ADH hormonal control
release is influenced by veno-arterial receptor traffic
delivered by cardiopulmonary baroreceptors
ANP hormonal control
released in response to atrial stretch
