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BIOM20002 - HSF > Lecture 63 - Filtration and Clearance > Flashcards

Lecture 63 - Filtration and Clearance Flashcards

1
Q

What happens to GFR when the afferent arteriole dilates?

A

GFR increases

NB as the arteriole dilates, the pressure of the blood in the glomerulus does not decrease.

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2
Q

What happens to renal blood flow when the afferent arteriole dilates?

A

Resistance decreases (Poiseuille’s equation)

Thus, blood flow increases

(Flow proportional inversely proportional to resistance)

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3
Q

What is the difference between plasma and blood?

A

Blood: plasma + RBC
Plasma: fluid component

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4
Q

What is Inulin used for?

Why?

A

GFR

Because:

  • not reabsorbed
  • not secreted
  • none metabolised
  • exogenous

Compare amount in the urine per unit time and the amount in the blood per unit time. This will give us GFR

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5
Q

What is renal clearance?

A

Rate of urinary excretion of a substance, relative to its plasma concentration

UV/P

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6
Q

In UV/P, what are the parameters?

A

U: concetration of substance in urine
V: volume of urine excreted per unit time

P: plasma concentration of substance

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7
Q

What happens to GFR when MAP increases?

How?

A

Stays the same
Kidneys regulate their blood flow to keep it roughly constant, despite MAP

Autoregulation:

  1. Myogenic response
  2. Tubuloglomerular feedback
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8
Q

What is the myogenic response?

Where does it happen?

A

In arterioles and small arteries

When there is stretch, the smooth muscle constricts

Mechanism:
• stretch
• ion channels open
• Ca2+ influx
• cross bridge cycling
• smooth muscle contraction
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9
Q

Describe tubuloglomerular feedback

A
  1. Increased pressure
  2. Increased GFR
  3. Increased flow past macula densa, nascent urine is more concentrated
  4. Paracrine diffuses from macula densa to afferent arteriole
  5. Afferent arteriole constricts
  6. Decrease in GFR
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10
Q

Which processes affect renal excretion?

A
  • RAAS
  • Sympathetic nervous system
  • Atrial natriuretic peptide
  • Vasopressin
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11
Q

What is the fundamental change that RAAS and sympathetic nervous system bring about?

A

Increase in BP

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12
Q

What are determinants of MAP?

A

CO

TPR

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13
Q

What element of the vasculature is most important for TPR?

A

Arterioles

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14
Q

What is atrial natriuretic peptide?

A

Natriuretic: excretion of Na+

Peptide from the atria of the heart that leads to salt excretion

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15
Q

Describe what happens in the atria with increased BP

A
  1. Increase BP in atria
  2. Stretch on atrial cells
  3. Release of natriuretic peptide (ANP)
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16
Q

What does stand for ANP?

A

Atrial natriuretic peptide

17
Q

What is vasopressin?

Describe its function

A

Also known as ADH

  1. Increased osmolarity of blood
  2. Detected by osmolarity receptors
  3. Release of ADH from posterior pituitary
  4. ADH acts on V2 receptor in collecting duct
  5. G-protein / cAMP system activated
  6. AQP2 put into apical membrane
  7. Increased water resorption
18
Q

Where does aldosterone come from?

A

Adrenal glands

19
Q

What is the action of Angiotensin II?

A
  1. Constriction of efferent arteriole
    • Increased GFR
  2. Increased resorption
20
Q

Where is renin released from?

A

Juxtaglomerular cells; specifically, granular cells in the afferent arterioles

21
Q

What hormones act on the proximal and distal nephron?

A

Proximal: angiotensin II
Distal: aldosterone

22
Q

What is the action of aldosterone on the nephron?

A

Increased Na resorption in distal nephron

  1. Diffuses into DCT cell
  2. Binds to Aldosterone receptor
  3. Acts as transcription factors
  4. Production of channels: Na+ and K+
    Increased Na/K ATPase activity
  5. Increased sodium reabsorption
23
Q

What is the action of NA on the nephron?

A
  1. Constriction of afferent arteriole

2. Increased Na resorption in PCT

24
Q

Where does Angiotensin II act?

A

Efferent arteriole

NB efferent more sensitive to A II than afferent

25
Q

Where does aldosterone act?

A

Distal nephron

26
Q

Where does noradrenaline act?

A

Afferent arteriole

PCT

27
Q

Where does ANP act?

A

Afferent arteriole

Collecting duct

28
Q

Describe the mechanism of action of ANP?

A
  1. Dilation of afferent arteriole
    Increased flow into glomerulus
    Increased GFR
  2. Collecting duct
    Inhibition of Na reabsorption

Inhibits:

  • ADH
  • Aldosterone
  • renin
29
Q

Do ANP and Angiotensin work together?

A

No, they are roughly antagonistic

30
Q

Describe the mechanism of RAAS

A
  1. Release of renin
  2. Angiotensinogen –> ANG I
  3. ANG I –> ANG II under ACE
  4. ANG II has many effects
  5. Increased BP
31
Q

What are the stimuli for release of renin?

A
  1. Decreased NaCl transport across macula densa
  2. Decreased stretch on granular cells
  3. Baroreceptor reflex
32
Q

What are the effects of ANG III?

A
  • vasoconstriction
  • ADH release
  • Aldosterone release
  • vasoconstriction of the afferent arteriole
  • increased reabsorption in the PCT
  • thirst
  • increased SNS activity
33
Q

Is aldosterone a short or long term response?

A

Long

Involves gene transcription

34
Q

What are the two main stimuli for aldosterone release?

A
  1. ANG II

2. Hyperkalaemia

35
Q

What are the stimuli for release of ADH / vasopressin?

A
  1. Increased osmolarity of the blood

2. ANG II

36
Q

What is the primary system for regulation of water balance?

What about salt balance?

A

Water balance: ADH / vasopressin

Salt balance: RAAS

37
Q

What affects NaCl transport across the Macula densa?

A

Decreased BP → Decreased GFR → Decreased NaCl transport

Increased BP → increased Transport

BIOM20002 - HSF (60 decks)

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