21. Renin-angiotensin-aldosterone system Flashcards Preview

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Flashcards in 21. Renin-angiotensin-aldosterone system Deck (32):

Angiotesin II activation axoin

Angiotensinogen (liver) + Renin --> Angiotensin I
Angiotensin I + ACE ( lungs and kindney ) ---> angiotensin II


renin is secreted by

juxtaglomerual kidney cells


renin seretion is triggered by

1. low blood pressure ( JG cells)
2. Low Na+ deliverly ( macula densa cells --> distal convoluted tubule)
3. increased sympathetic tone ( β1-receptors)


increased sympathetic tumors increase Renin secretion via .... receptors



angiotensin - converting enzyme - location

capillaries of the lungs but can also be found in endothelial and kidney epithelial cells


beside its action in agiotensin - aldosteron axons , ACE also

causes Bradykinin breakdown


Angioensin II action

1. acts at angiotensin II receptor ( type 1-AT1) on vascular SMC --> vasoconstriction --> increases BP
2. constricts EFFERENT arteriole of glomerus --> increaes
Filtration fraction to preserve GFR in low volumes states ( eg. when low RBF)
3. Aldosterone secretion ( adrenal gland ) --> increases NA channel and Na/K pump in principal cells b. enhance K+ and H+ excretion by way of principal cell K channels and α- intercalated cells H+ ATPase --> creates favorable Na+ gradient for Na and H2O reabsorption
4. ADH posterior pituitary --> increases aquaporin insertion in principal cells --> H2o reabsorption
5. increases pCT Na/H+ exchanger activity --> Na+. HCO3- and H2O reabsorption --> permit contraction alkalosis
6. Stimulates hypothalamus --> thirst


angiotensin action on vessles

1. acts at angiotensin II receptor ( type 1-AT1) on vascular SMC --> vasoconstriction --> increases BP
2. constricts EFFERENT arteriole of glomerus --> increaes
Filtration fraction to preserve GFR in low volumes states ( eg. when low RBF)


angiotensin action on CNS

1. ADH posterior pituitary ---> increases aquaporin insertion in principal cells--> H2o reabsorption
2. Stimulates hypothalamus --> thirst


angiotensin action on PCT

Na/H+ exchanger activity ---> Na+, HCO3- and H2O reabsorption ---> permit contraction alkalosis


angiotensin action on adrenal gland

activates aldosterone synthase ( zona gloemerulosa) --> aldosterone secretion


in addition to its pressor efect, ATII also

affects baroreceptor function --> limits reflex bradycardia which would normally accompany its pressor effects


ADH primary regulates .... also respond to ......

low blood volume sttates


ANP and BNP are released from ........( and when )

from atria ( ANP) and ventricle ( BNP0 in response to increased volume --> may act as a check of renin - angiotensin - aldosterone system


ANP and BNP - action

1. relaxes vasculae smooth muscle via cGMP ---> increase GFR and decrease Renin
2. dilates afferebt arteruike, constricts efferent arteriole and promote natriuresis


• What five actions of angiotensin II increase intravascular volume and blood pressure?

Vasoconstriction, increased PCT Na+ reabsorption, adrenal cortex aldosterone release, pituitary ADH release, thirst (drinking more water)


• A patient is found to have decreased renin activity. Where would this defect have consequences in the RAAS system?

It causes a backup of angiotensinogen from the liver and decreased angiotensin I


• What are the two main sources of angiotensin-converting enzyme (ACE)? What is their effect on angiotensin I?

Lung and kidney epithelia; they cleave angiotensin I into angiotensin II


• For unknown reasons, an inpatient has high plasma renin. An attending asks you for causes; what four responses could you propose?

A decrease in blood pressure, a decrease in distal Na+ macula densa delivery, an increase in sympathetic tone, or a renin-secreting tumor


• One action of angiotensin II is stimulation of the release of aldosterone from the ____.

Adrenal gland


• Antidiuretic hormone (ADH) mainly regulates ____ (osmolarity/blood volume); aldosterone mainly regulates ____ (osmolarity/blood volume).

Osmolarity; blood volume


• A patient is in hemorrhagic shock with iso-osmolar volume loss. ADH will be (low/high) and aldosterone will be (low/high)

High; high (both rise in states of severe volume depletion)


• What hormone, released from the atria, may act as a check on the renin-angiotensin system to prevent volume overload?

Atrial natriuretic peptide (ANP)


• How does aldosterone secretion from the adrenal gland create favorable conditions for salt and water retention?

Increases number of luminal sodium channels and basolateral sodium-potassium antiporters, and water passively follows sodium influx


• Atrial natriuretic peptide (ANP) ____ (increases/decreases) renin secretion and ____ (dilates/constricts) afferent arterioles.

Decreases; dilates


• An experimental drug blocks the activity of atrial natriuretic peptide (ANP). How does this affect the glomerular filtration rate (GFR)?

Decreases the GFR, because dilation of afferent arteriole (action of ANP) is inhibited


• Decreased Na+ delivery to the ____ (juxtaglomerular apparatus [JGA]/macula densa) triggers renin release from the ____ (JGA/macula densa).

Macula densa (a sodium sensa); JGA


• Which hormone in the renin-angiotensin-aldosterone system alters baroreceptor responses to prevent reflex bradycardia?

Angiotensin II (otherwise, the increase in blood pressure caused by angiotensin II would lead to a slower heart rate


• A drug blocks AT II production, causing bradykinin-induced flushing. How is AT II inhibited, and why is bradykinin increased?

Via an angiotensin-converting enzyme (ACE) inhibitor; ACE, which breaks down bradykinin, is blocked by ACE inhibitors, so bradykinin rises


• How does angiotensin II (AT II) promote contraction alkalosis?

Increases PCT Na+/H+ activity, promoting reabsorption of HCO3-, Na+, and water, ultimately promoting contraction alkalosis


• What hormone, released by the ventricles, acts very similarly to ANP? By way of what second messenger system do both of these hormones act?

BNP; via cGMP (relaxes smooth muscle)


• Name the three stimuli that upregulate renin activity.

Decreased BP (detected by JG cells), decreased Na+ delivery to macula densa, increased sympathetic tone via β1-receptors

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