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Human physiology (2) > Hormonal control of the kidney > Flashcards

Hormonal control of the kidney Flashcards

1
Q

What us the % of sodium reabsorbed in:

a) The PCT
b) Thick ascending limb
c) DCT
d) Top of collecting duct
e) bottom of collecting duct

A

a) PCT: 60-70% reabsorbed
b) TAL: 25% reabsorbed
c) DCT: 6% reabsorbed
d) T CD: 2% reabsorbed
e) B CD: <1% reabsorbed

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2
Q

What does RAAS stand for?

A

Renin-Angiotensin-Aldosterone-System

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3
Q

What is renin?

A

Renin is an enzyme contained within specialised smooth muscle cells in the walls of afferent and efferent arterioles

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4
Q

How is renin stimulated? (3)

A

> Reduced perfusion pressure in the afferent arteriole
Increased sympathetic nerve activity in fibres innervating efferent and efferent arterioles
Decreased Na+ concentration flowing through DCT

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5
Q

What is the role of a renal baroreceptor?

A

Decrease renal perfusion (pressure in vessels sensed by renin-secreting cells) leading to increased renin release

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6
Q

What is the role of a catecholamines?

A

Beta-adrenoreceptor stimulation leads to increased renin release

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7
Q

What is the role of macula densa mechanisms?

A

Sense a decrease in Na+ delivery to distal tubule, ;ending to increased renin release

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8
Q

How does renin effect the function of blood volume and pressure? (8)

A
  1. Angiotensinogen + Renin
  2. Angiotensin 1
  3. Angiontensin 2
  4. Adrenal gland
  5. Aldosterone
  6. Increased Na+ and H2O reabsorption in distal tubes
  7. Homeostasis blood pressure volume (low vol or high pressure)
  8. Change will occur
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9
Q

What is angiotensin 2 and what does it stimulate (2)?

A

Angiotensin 2 increases blood pressure by constricting arterioles

  • Stimulates reabsorption of Na+
  • Stimulates the release of the hormone aldosterone from the adrenal gland, acts of DCT to increase Na+ and H2O reabsorption. Blood vol. and pressure increase
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10
Q

What is aldosterone?

A

Steroid hormone released from zona glomerulosa of adrenal cortex

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11
Q

What is the function of aldosterone? (2)

A
  • Increases in plasma K+ and angiotensin 2 or decreases in plasma Na+ lead to elevated levels of aldosterone
  • Acts via intracellular receptors in the DCT to increase Na+ channels - water follows
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12
Q

What are the consequences of aldosterone? (3)

A

Na+ retention
K+ loss
H+ loss

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13
Q

What is the Na+ largely controlled by?

A

Aldosterone

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14
Q

What happens when there is a decrease in blood pressure in the RAAS? (3)

A
  • Reduced pressure near DCT stimulates release of renin from juxtaglomerular apparatus
  • RAAS acts to increase permeability in the collecting duct, increasing blood volume and causing vasoconstriction
  • Result is elevation in blood pressure
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15
Q

How does RAAS contribute to aldosterone production? (2)

A
  • Angiotensin 2 causes adrenal gland to secrete aldosterone

- Helps to increase reabsorption of Na+

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16
Q

How does the RAAS contribute to volume sensors?

A

Renin rebased in response to low body fluid osmolality, low blood volume, low blood pressure

17
Q

What is the effect of ADH/vasopressin? (2)

A
  • Acts on the DCT to regulate filtrate volume and osmolality
  • Changes in osmolality of body fluids are sensed by osmoreceptors in the hypothalamus which trigger release of ADH from stores in posterior pituitary
18
Q

What senses a decrease in blood volume?

A

Cardiopulmonary baroreceptors - increase ADH release

19
Q

How does ADH regulate water loss? (2)

A

Increase permeability to water in collecting duct

Produces concentrated urine

20
Q

What is the primary function of ADH?

A

Regulate extracellular fluid volume by affecting renal handling of water - acts on V2 receptors on renal collecting ducts

21
Q

What happens when ADh is at high and low levels?

A

High levels of ADH: More water is reabsorbed and less is excited
Low levels of ADH: Large volume of water are excreted (hydrated)

22
Q

What are the 2 modes of action from ADH stimulation?

A

V1 - vasoconstriction - increased arterial pressure

V2 - renal fluid reabsorption - increased blood volume - increased arterial pressure

23
Q

What is ANP?

A

Atrial natriuretic peptide - hormone released in response to an increase in blood volume and pressure

24
Q

Where is ANP released?

A

Released by cardiac atrial cells when stretched - volume overload

25
Q

What is the effect of ANP? (4)

A

> Opposes the RAAS and inhibits the release of renin
Causes Na+ and water loss by inhibiting aldosterone
Increases GFR
Also acts as a vasodilator

26
Q

What does ANP counteract?

A

Counteracts the vasoconstrictor actions of sympathetic renal nerves and angiotensin 2

27
Q

What is the purpose of ANP?

A

Promotes sodium excretion and water excretion to counteract changes in blood volume and pressure

Human physiology (2) (22 decks)

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