Physiology : Renin Angiotensin System

Question 1

What are the components of the Renin angiotensin Aldosterone system ?
how does it work ?

Answer 1

1) BP drops
2)Sympathetic nervous system is activated = fight or flight
3)Kidneys are stimulated =>cells called juxtaglomerular cells(JG cells) PRODUCE RENIN
3)RENIN Activates angiotensinogen in liver
4)This forms angiotensin 1
5)vascular endothelial cells in lung = Angiotensin-converting Enzyme = ACE enzyme converts angiotensin 1 –>angiotensin 2
6)Angiotensin 2 = vasoconstrictor ! increases blood volume and blood pressure ! It has the following functions :
1-Causes kidney to keep Na+=increase water retention
2-Adrenal gland releases ALDOSTERONE =Retains na+ and secretes k+
=water retention
3-pituitary gland releases ADH ( vasopressin )which increases thirst , and tells Kidney to hold onto the water !

Question 2

what is the role of RAAS ?

4

Answer 2

• increases water retention , -blood pressure
• blood volume !
• increases angiotensin 2 =vasoconstrictor

Question 3

how can we suppress RAAS activity ?

4

Answer 3

1-Beta adrenergic blockers :(noradrenaline binds here ) Beta receptors on JG cells cause release of renin , so if they’re blocked , renin decreases !
2-Renin inhibitors
3-ACE inhibitors (enzyme that converts angiotensin 1–>2)
4-AT receptor antagonists and blockers

Question 4

pharmacological classification of angiotensin receptors , tissue distribution effects associated with each subtype
(6)

Answer 4

ANGIOTENIS 2 BINDS TO BOTH RECEPTORS BELLOW:

1=AT1 receptor causes vasoconstriction( most common one)

• smooth muscle
• G protein linked to phospholipase C in vascular smooth muscle )
• increase ca2+ = contraction increases
• activates tyrosine kinases too

2=AT2 receptor causes vasodilation (less common in adults)

• G-protein linked too
• antagonise growth effect
• open K+ channels
• increases NO production = vasodilation

Question 5

role of ADH (vasopressin)

4

Answer 5

• Anti diuretic hormone released from pituitary glad
• causes kidney to retain na+ and hence water retention
• also increases thirst

Question 6

how can overactivity of RAAS be bad ?

2

Answer 6

• Hypertension !

- causes many cardiovascular problems !

Question 7

how is renin released ( 3 ways)

6

Answer 7

1) baroreceptors in kidney = detect low pressure in AFFERENT ARTERIOLE =cuases release of renin from JG cells
2) Sympathetic nerve mechanism = Beta adrenergic receptors on JG cells cause renin release

3)Macula densa mechanism
these are chemoreceptors which detect change in pH –>prostaglandin is released –>travels to JG cells–>increases cAMP–>causes renin release from granules !