RAAS

Question 1

What does RAAS stand for

Answer 1

Renin-Angiotensin-Aldosterone System

Question 2

What is the role of RAAS

Answer 2

Essential for regulation of blood pressure and fluid balance

Question 3

What are the hormones of the RAAS system

Answer 3

Renin

Angiotensin II

Aldosterone

Question 4

What is RAAS primarily regulated by

Answer 4

Renal blood flow

Question 5

What is the first stage of RAAS

Answer 5

Renin release

Question 6

Where is renin released

Answer 6

Granular cells of the juxtaglomerular apparatus (JGA)

Question 7

What are the 3 factors which result in the release of renin

Answer 7

1. reduced sodium delivery to the distal convoluted tubules
2. reduced perfusion pressure in the kidney
3. sympathetic stimulation of juxtaglomerular apparatus

Question 8

How is reduced sodium delivery to the distal convoluted tubules detected

Answer 8

By macula densa cells

Question 9

How is reduced perfusion pressure in the kidney detected

Answer 9

By baroreceptors in the afferent arteriole

Question 10

How is sympathetic stimulation of juxtaglomerular apparatus completed

Answer 10

Via B1 adrenoreceptors

Question 11

What is the release of renin inhibited by

Answer 11

Atrial natriuretic peptide

Question 12

When is ANP released

Answer 12

Stretch in the atria in response to increased blood pressure

Question 13

What is angiotensinogen

Answer 13

Precursor protein produced in the liver

Question 14

How is angiotensin I formed

Answer 14

Angiotensinogen cleaved by renin

Question 15

How is angiotensin II formed

Answer 15

Angiotensin I converted by angiotensin converting enzyme (ACE)

Mainly occurs in the lungs where ACE is produced by vascular endothelial cells

Question 16

How does angiotensin II exert its action

Answer 16

By binding to various receptors throughout the body

Question 17

What receptors does angiotensin II bind to

Answer 17

One of two G-protein coupled receptors

AT1 and AT2 receptors

Question 18

Where does most angiotensin II bind to

Answer 18

AT1 receptor

Question 19

In the adrenal cortex what is the action of angiotensin II

Answer 19

Stimulates release of aldosterone

Question 20

In the hypothalamus what is the action of angiotensin II

Answer 20

Increase thirst sensation
- increase fluid consumption
- raises circulating volume = increase BP

Stimulates anti-diuretic hormone (ADH) release ( posterior pituitary gland)
- production of more concentrated urine
- reduce loss of fluid

Question 21

In the kidney what is the main action of angiotensin II

Answer 21

Stimulates NA+ reabsorption

Question 22

In the arterioles what is the main action of angiotensin II

Answer 22

Vasoconstriction

Question 23

In the sympathetic nervous system what is the main action of angiotensin II

Answer 23

Increased release of noradrenaline (fight or flight)
- increase cardiac output
- vasoconstriction of arterioles
- release of renin

Question 24

What are the areas of the kidney that angiotensin II targets

Answer 24

Renal artery and afferent arteriole

Efferent arteriole

Mesangial cells

Proximal convoluted tubule

Question 25

Describe the affect of angiotensin II on the renal artery and afferent arteriole

Answer 25

Vasoconstriction

Question 26

Describe the affect of angiotensin II on the efferent arteriole

Answer 26

Vasoconstriction (greater than the afferent arteriole)

Question 27

Describe the affect of angiotensin II on the mesangial cells

Answer 27

Contraction, leading to a decreased filtration rate

Question 28

Describe the affect of angiotensin II on the proximal convoluted tubule

Answer 28

Increased Na+ reabsorption

Question 29

What does angiotensin also play an important role in

Answer 29

Tubuloglomerular feedback Helps maintain a stable GFR

Question 30

What does angiotensin II act on to stimulate the release of aldosterone

Answer 30

Adrenal cortex

Question 31

Describe aldosterone

Answer 31

Mineralocorticoid Steroid hormone released from the zona glomerulosa of the adrenal cortex

Question 32

What does aldosterone act on

Answer 32

Principal cells of the collecting ducts in the nephron

Question 33

What is the action of aldosterone

Answer 33

Increases expression of apical epithelial Na+ channels to reabsorb urinary sodium

Question 34

What can aldosterone cause

Answer 34

Increased levels can cause reduced levels of potassium in blood due to increased activity of sodium/potassium pump

Question 35

What is ADH also known as

Answer 35

Vasopressin

Question 36

What is ADH secreted by

Answer 36

Posterior pituitary gland

Question 37

What controls the release of ADH

Answer 37

Changes in plasma osmotic pressure and volume status Other factors - exercise - angiotensin II - emotional state e.g. pain

Question 38

What is ADH release inhibited by

Answer 38

ANP

Question 39

ADH What would a fall in plasma volume cause

Answer 39

Would be an increase in plasma sodium concentration = increase in osmolarity Water moves down its concentration gradient into the plasma Stimulates osmoreceptors to control Increases release of ADH

Question 40

ADH What would an increase in plasma volume cause

Answer 40

Reduce plasma osmolarity Osmoreceptors cells would expand - water moves down its concentration gradient out of the plasma Decrease release of ADH

Question 41

Where are signals for ADH sent

Answer 41

Afferent signals from hypothalamus to posterior pituitary

Question 42

Where does ADH act

Answer 42

Distal convoluted tubule Collecting ducts

Question 43

How does ADH act

Answer 43

Increased plasma osmolarity Through G-protein coupled receptors to increase insertion of Aquaporin-2 channels to the apical membrane of the DCT and CD cells

Question 44

Describe ACEi (inhibitors)

Answer 44

Inhibit action of angiotensin converting enzyme so reduce levels of angiotensin II in the body - decreased arteriolar resistance - decreased arteriolar vasoconstriction - decreased cardiac output - reduces potassium excretion in the kidneys