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Kidney > RAAS > Flashcards

RAAS Flashcards

1
Q

What does RAAS stand for

A

Renin-Angiotensin-Aldosterone System

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2
Q

What is the role of RAAS

A

Essential for regulation of blood pressure and fluid balance

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3
Q

What are the hormones of the RAAS system

A

Renin

Angiotensin II

Aldosterone

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4
Q

What is RAAS primarily regulated by

A

Renal blood flow

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5
Q

What is the first stage of RAAS

A

Renin release

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6
Q

Where is renin released

A

Granular cells of the juxtaglomerular apparatus (JGA)

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7
Q

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

A
  1. reduced sodium delivery to the distal convoluted tubules
  2. reduced perfusion pressure in the kidney
  3. sympathetic stimulation of juxtaglomerular apparatus
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8
Q

How is reduced sodium delivery to the distal convoluted tubules detected

A

By macula densa cells

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9
Q

How is reduced perfusion pressure in the kidney detected

A

By baroreceptors in the afferent arteriole

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10
Q

How is sympathetic stimulation of juxtaglomerular apparatus completed

A

Via B1 adrenoreceptors

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11
Q

What is the release of renin inhibited by

A

Atrial natriuretic peptide

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12
Q

When is ANP released

A

Stretch in the atria in response to increased blood pressure

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13
Q

What is angiotensinogen

A

Precursor protein produced in the liver

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14
Q

How is angiotensin I formed

A

Angiotensinogen cleaved by renin

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15
Q

How is angiotensin II formed

A

Angiotensin I converted by angiotensin converting enzyme (ACE)

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

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16
Q

How does angiotensin II exert its action

A

By binding to various receptors throughout the body

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17
Q

What receptors does angiotensin II bind to

A

One of two G-protein coupled receptors

AT1 and AT2 receptors

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18
Q

Where does most angiotensin II bind to

A

AT1 receptor

19
Q

In the adrenal cortex what is the action of angiotensin II

A

Stimulates release of aldosterone

20
Q

In the hypothalamus what is the action of angiotensin II

A

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

21
Q

In the kidney what is the main action of angiotensin II

A

Stimulates NA+ reabsorption

22
Q

In the arterioles what is the main action of angiotensin II

A

Vasoconstriction

23
Q

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

A

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

24
Q

What are the areas of the kidney that angiotensin II targets

A

Renal artery and afferent arteriole

Efferent arteriole

Mesangial cells

Proximal convoluted tubule

25
Q

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

A

Vasoconstriction

26
Q

Describe the affect of angiotensin II on the efferent arteriole

A

Vasoconstriction (greater than the afferent arteriole)

27
Q

Describe the affect of angiotensin II on the mesangial cells

A

Contraction, leading to a decreased filtration rate

28
Q

Describe the affect of angiotensin II on the proximal convoluted tubule

A

Increased Na+ reabsorption

29
Q

What does angiotensin also play an important role in

A

Tubuloglomerular feedback

Helps maintain a stable GFR

30
Q

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

A

Adrenal cortex

31
Q

Describe aldosterone

A

Mineralocorticoid

Steroid hormone released from the zona glomerulosa of the adrenal cortex

32
Q

What does aldosterone act on

A

Principal cells of the collecting ducts in the nephron

33
Q

What is the action of aldosterone

A

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

34
Q

What can aldosterone cause

A

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

35
Q

What is ADH also known as

A

Vasopressin

36
Q

What is ADH secreted by

A

Posterior pituitary gland

37
Q

What controls the release of ADH

A

Changes in plasma osmotic pressure and volume status

Other factors
- exercise
- angiotensin II
- emotional state e.g. pain

38
Q

What is ADH release inhibited by

A

ANP

39
Q

ADH

What would a fall in plasma volume cause

A

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

40
Q

ADH

What would an increase in plasma volume cause

A

Reduce plasma osmolarity

Osmoreceptors cells would expand - water moves down its concentration gradient out of the plasma

Decrease release of ADH

41
Q

Where are signals for ADH sent

A

Afferent signals from hypothalamus to posterior pituitary

42
Q

Where does ADH act

A

Distal convoluted tubule

Collecting ducts

43
Q

How does ADH act

A

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

44
Q

Describe ACEi (inhibitors)

A

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

Kidney (7 decks)

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