Cardio 9 Flashcards
Describe RAAS.
‘Renin-Angiotensin-aldosterone-system’
-slower than baroreceptor bc is hormonal
-activated in response to decrease in MAP
-responses that attempt to restore arterial pressure to normal
Describe what happens when there’s a decrease in MAP.
-causes decrease in renal perfusion pressure
-sensed by mechanoreceptors in kidney
-baroreceptors are in walls of afferent arterioles of kidney
>detect changes in BP
>message sent to juxtaglomerular cells/granular cells
Describe juxtaglomerular cells.
-secrete renin
-enzyme catalyses conversion of angiotensinogen to angiotensin I
>decrease in BP (hypotension) stimulates release of renin
>renin secretion is increased by sympathetic activation & decrease in Na levels
-in lungs & kidneys Angiotensin I is converted to angiotensin II
>catalyzed by angiotensin converting enzyme (ACE)
Describe what happens when there’s a decrease in renal perfusion.
Describe angiotensin II.
peptide with biological actions in:
-adrenal cortex
-vascular smooth muscle
-kidneys
-brain
-heart
Ang II binds to AT1
Describe the zona glomerulosa cells of the adrenal cortex.
-angiotensin II acts on these cells
-stimulates production of aldosterone
>mineralocorticoid
>requires gene transcription & new protein synthesis
-act on principle cells of renal distal tubule & collecting duct
-increases Na, Cl, & H2O absorption & excretion of K+
>increases blood volume
Describe the effect angiotensin II has on the kidney.
-stimulates Na & H+ ion exchange in renal proximal tube
-increase reabsorption of Na & bicarbonate
maintains pH
Describe how angiotensin II acts directly on the arterioles.
-by binding to AT1R
-activates IP3/Ca second messenger system = causes vasoconstriction
-increase total peripheral resistance & increase MAP
Describe how angiotensin II acts on the hypothalamus.
-increases thirst & water intake
-hypothalamus = body’s ‘thirst center’
>osmoreceptors (chemoreceptor) = senses change in ECF osmolality (amount of solutes in blood/osmotic pressure)
>cerebral & peripheral osmoreceptors = water balance
>decrease in blood volume or increase [Na] stimulates water ingestion
Describe angiotensin II & ADH.
-angiotensin II stimulates secretion of ADH
-ADH is produced by neuro-hypophysis & increases water reabsorption in kidney
-by increasing total body water = effect complement aldosterone effects
>increase ECF volume, blood volume & BP
Describe how ADH increases water reabsorption.
- Vasopressin binds to membrane receptor
- Receptor activates cAMP second messenger system
- Cell inserts AQP2 water pores into membrane
- Water absorbed by osmosis into blood
Describe angiotensin II & contractility.
-angiotensin II increases contractility
-causes vascular & cardiac hypertrophy & myocardial fibrosis
Describe the effect of RAAS in increasing MAP.
What aids in regulating MAP?
- ADH
- Atrial natriuretic peptide
- Chemoreceptors for O2
- Chemoreceptors for CO2
Describe cardiopulmonary low pressure baroreceptors.
-sense changes in blood volume
-located in veins, atria, pulmonary arteries
-called ‘cardiopulmonary volume receptors’
-located in venous side of circulation
Describe the relationship between blood volume & CVP.
-when blood volume increases, CVP increases
-cardiopulmonary volume receptors return volume to normal
>increases excretion of Na & water
How do cardiopulmonary volume receptors interfere with BP?
How do peripheral chemoreceptors interfere with BP?
How do central chemoreceptors interfere with BP?
