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Physiology #5 > RP5: Regulation of Tubular Reabsorption > Flashcards

RP5: Regulation of Tubular Reabsorption Flashcards

1
Q

What are the local control mechanisms for tubular reabsorption?

A

➢ Tubuloglomerular Feedback Response (TGF)
➢ Glomerulotubular Balance (GTB)
➢ Pressure natriuresis/diuresis

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2
Q

What is the tubuloglomerular feedback response (TGF)?

A

Autoregulation of GFR.
➢ Keeps GFR constant
➢ Afferent and Efferent arteriolar resistance related to flow rate of NaCl by macula densa
➢ Example: GFR increase-increased NaCl to macula densa- TGF response decreases GFR

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3
Q

What is the glomerular tubule balance (GTB)?

A

Autoregulation
of PT reabsorption rate
➢ PT reabsorption rate related to tubular load
➢ As tubular LOAD increases, rate of REABSORPTION increases.
➢ Depends on changes in peritubular capillary and renal interstitial fluid Starling’s forces.
➢ Example: GFR increase-GT balance increases PT Na+/H20 reabsorption to maintain Na+/H20 balance

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4
Q

What do TGF and GTB together prevent?

A

prevent overloading of the distal tubule segment when GFR increases due to pressure changes or other disturbances

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5
Q

What does pressure natriuresis ensure?

A

assure that large changes in salt and water intake accommodated with only minor changes in ECF volume, CO, and MAP

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6
Q

What are the systemic control hormones that regulatetubular reabsorption?

A

aldosterone
angiotensin II
antidiuretic hormone (ADH)
atrial natriuetic peptide (ANP)

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7
Q

What is the local effector response of aldosterone?

A

➢ Stimulates Na+ Reabsorption
➢ Stimulates K+ Secretion
➢ Stimulates H+ Secretion
(α-Intercalated cells)

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8
Q

What is the systemic effector response for aldosterone?

A

➢ increase Na+
➢ decrease K+
➢ increase ECF pH

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9
Q

What controls the release of aldosterone?

A

Increase release of aldosterone
- increased Ang II
- increased K+
- increased H+

Decrease the release of aldosterone
- increased ANP
- increased Na (weak inhibitor)

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10
Q

What is the mechanistic explanation for why aldsterone has a slow onset and long duration response?

A
  • slow onset since it takes 2 hours to change gene expression
  • long duration since steroid hormones don’t like water so they are bound to proteins which increases their half-life
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11
Q

When is ANP secreted?

A

volume increases

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12
Q

What is aldosterone a regulator of?

A

ECF Osmolarity

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13
Q

What is angiotensin II a regulator of?

A

ECF volume, ECF osmolarity, and TPR

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14
Q

What is the local effector response for angiotensin II?

A

➢ Stimulates aldosterone production and secretion from Zona Glomerulosa.
➢ Directly increases Na+
reabsorption
➢ Increases H+ secretion
➢ Constricts efferent arterioles; increase GFR
➢ Constricts systemic arterioles
➢ Increases thirst
➢ Increases ADH Secretion

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15
Q

What is the systemic effector response for angiotensin II?

A
  • increase ECF volume
  • increase TPR
  • increase MAP
  • increase pH
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16
Q

What controls renin secretion which in turn controls angiotensin II secretion?

A

Increases renin/angiotensin II
- decreased MAP
- decreased blood volume
- decreased renal blood flow
- increased sympathetic activity
- decreased NaCl delivery to macular densa (TGF)

Decreases renin/angiotensin II
- increased ANP

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17
Q

What is ADH a regulator of?

A

ECF Volume and Osmolarity

18
Q

What is the local effector response for ADH?

A

increased H2O Reabsorption in Distal nephron

19
Q

What is the systemic effector response for ADH?

A

increased ECF volume
decreased ECF Osmolarity
increased MAP

20
Q

What is the mechanism of ADH?

A

➢ Activation of Gαs Protein linked
receptor
➢ Increases the synthesis and insertion of AQP-2 into luminal membrane.

21
Q

Where does ADH have effects in the nephron?

A

Late Distal Tubule
Collecting Duct

22
Q

Where does aldosterone have effect in the nephron?

A

principal cell
alpha intercalated

23
Q

Where does angiotensin II have effect in the nephron?

A

Prox tubule
TAL of Henle
distal tubule
collecting duct

24
Q

What controls the secretion of ADH?

A

Increased secretion of ADH
- increase ECF osmolarity
- decreased blood volume
- decresead blood pressure
- nausea
- hypoxia
- nicotine and morphine
- angiotensin II
- ecstasy

Decreased secretion of ADH
- ethanol
- cold

25
Q

What does atrial natriuretic peptide (ANP) regulate?

A

ECF volume

  • only hormone we discussed that decreases blood pressure
26
Q

What controls the secretion of ANP?

A

Increased secretion of ANP
- cardiac atria stretching due to blood volume increase

Decreased secretion of ANP
- decreased blood volume

27
Q

What is the local effector response for ANP?

A

➢ Directly inhibits Na+ and H2O reabsorption in PT
➢ Increases GFR (dilates afferent, constricts efferent arterioles).
➢ Inhibits renin release and aldosterone formation.
➢ Helps to minimize blood volume expansion (CHF).

28
Q

What is the systemic effector response to ANP?

A
  • decreased ECF osmolarity
  • decreased blood volume
29
Q

Where does ANP have an effect in the nephron?

A

proximal tubule

30
Q

What is aldosterone escape?

A

the sodium excretion returns to normal even though MAP is high

31
Q

What causes aldosterone escape?

A
  • increasing ANP
  • increasing pressure natriuresis
32
Q

Which disease is characterized by hyperaldosteronism?

A

Conn’s syndrome

33
Q

What does the sympathetic nervous system regulate in the renal system?

A

ECF Volume and MAP

34
Q

What is the local effector response of the sympathetic nervous system?

A

➢ Constricts arterioles
➢ Stimulates renin release.
➢ increases RAA and increases REA (Decreases GFR and
renal blood flow)
➢ Directly stimulates Na+ reabsorption via α receptors on tubule epithelial cells in PT and TAL.

35
Q

What is the systemic effector response for the sympathetic nervous system?

A
  • increased ECF volume
  • increased TPR
  • increased MAP
36
Q

What increases the response of the sympathetic nervous system?

A
  • decreased MAP
  • increased stress
37
Q

What is the effect of aldosterone?

A

↑ NaCl, H2O reabsorption
↑ K+ secretion
↑H+ secretion

38
Q

What is the effect of angiotensin II?

A

↑ NaCl
↑ H2O reabsorption
↑ H+ secretion

39
Q

What is the effect of ADH?

A

↑ H2O reabsorption

40
Q

What is the effect of ANP?

A

↓ NaCl reabsorption

Physiology #5 (9 decks)

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