Page 1030 - Fundamentals of anatomy physiology

Chapter 26 The Urinary System 1017

Figure 26–11 The Response to a Reduction in the GFR.

Renin–Angiotensin-Aldosterone System

Integrated endocrine and
neural mechanisms activated

Endocrine Renin in the bloodstream Angiotensin II triggers
response triggers formation of increased aldosterone
Juxtaglomerular
complex increases angiotensin I, which is then secretion by the
production of renin activated to angiotensin II adrenal glands
by angiotensin converting
Aldosterone
enzyme (ACE) in the increases
capillaries of the lungs Na+ retention
Increased fluid
Angiotensin II constricts consumption Angiotensin II
peripheral arterioles and Increased fluid triggers
retention neural
further constricts the Constriction of
efferent arterioles venous reservoirs responses

if insufficient to restore normal GFR HOMEOSTASIS Increased Increased Increased
RESTORED systemic blood stimulation of
Increased volume thirst centers
glomerular blood Increased ADH
pressure pressure
production
Increased
cardiac output Increased
sympathetic
motor tone

Together, angiotensin II
and sympathetic activation

stimulate peripheral
vasoconstriction

Autoregulation HOMEOSTASIS 26
RESTORED
Immediate local if sufficient
response in the Normal
kidney GFR

Increased
glomerular
blood pressure

Dilation of HOMEOSTASIS Start HOMEOSTASIS
afferent arterioles DISTURBED Normal

Contraction of Decreased GFR glomerular
mesangial cells resulting in filtration rate

Constriction of decreased filtrate
efferent arterioles and urine
production