R e n i n - a n g i o t e n s i n - a l d o s t e r o n e s y s t e m
F i g u r e 1 5 . 1 3
In a complex series of events involving several organs, the renin-angiotensin-
aldosterone system increases sodium and water reabsorption in the kidney
and restores blood volume and blood pressure.
Afferent
arteriole
Juxtaglomerular cell
2.
The liver makes a
protein called
angiotensinogen
and releases it into
the blood.
3.
In the blood, renin converts
.>.
angiotensinogen into
andiotensin
I.
1.
When blood volume and pressure
decrease, the walls of the afferent
arteriole stretch less and cause the
juxtaglomerular cells
(specialized
cells in the afferent arteriole) to secrete
renin
.
6.
All constricts
blood vessels.
4.
As the blood passes
through the lungs, another
enzyme called
angiotensin converting
enzyme (ACE)
converts
angiotensin I into an
active protein called
angiotensin II (All).
5.
All constricts
afferent arterioles
and reduces GFR.
t
7.
All stimulates Na+, Cl-,
and water reabsorption
in PCT.
V
10.
The increased reabsorption
of Na+ and water increases
blood volume
.
8.
All acts on the
adrenal cortex to
release
aldosterone
.
Adrenal cortex
9.
Aldosterone stimulates Na
reabsorption and K+ excretion
in principal cells of DCT and
collecting ducts. Water gets
osmotically reabsorbed in
response to Na+ reabsorption.
t
11.
Increased blood volume and vasoconstriction
restore blood pressure
.
Excess secretion of aldosterone might result
in depletion of which of the following ions?
a. K+
b. Ca2+
c. Na+
d. Mg2+
V____________________________________
J
The Kidneys Regulate the Composition of Body Fluids 457
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