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Renal Physiology > Regulation of Salt & H20 Balance > Flashcards

Regulation of Salt & H20 Balance Flashcards

1
Q

Na+ load = …

A

ECF = Blood P

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2
Q

When there is a HIGH Na+ load, …

A

Increased H20 reabsorption

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3
Q

When there is a LOW Na+ load, …

A

Decreased H20 reabsorption

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4
Q

Granular cells (in the Juxtaglomerular apparatus) secrete renin in response to…

A

Decreased NaCl

Decreased ECF volume

Decreased Blood P

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5
Q

What are the 3 mechanisms of renin release?

A
  1. Granular cells are BARORECEPTORS
  2. Macula Densa cells detect NaCl in tubule (DCT)
  3. Granular cells are innovated by SNS
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6
Q

When there is decreased NaCl/ECF vol./Arterial B.P. , which hormone release pathway is stimulated? Explain this pathway.

A

RAAS pathway.

  • Liver releases Angiotensiongen
  • Kidney releases Renin
  • Lungs release ACE

Angiotensiongen –> Angiotensin 1
(by Renin)

Angiotensin 1 –> Angiotensin 2
(by Angiotensin Converting Enzyme [ACE])

Angiotensin 2 –> Aldosterone (BY ADRENAL GLAND)
~> Vasopressin
~> Thirst
~> Arteriolar vasoconstriction

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7
Q

Angiotensin 2 –> Aldosterone (BY ADRENAL GLAND)
~> Vasopressin
~> Thirst
~> Arteriolar vasoconstriction

Discuss the outcomes that follow.

A

Aldosterone –> Na+ reabsorption (increased Cl- reabsorption follows passively) –>

Na+ (& Cl-) conserved –>

Na+ (& Cl-) osmotically hold more H20 in ECF –>

H20 conserved

~Vasopressin --> Increased H20 reabsorption -->
   H20 conserved ~***Thirst --> Increased fluid intake --> ~***Art. vasocon. -->

~*** LEAD TO THE REVERSAL OF
decreased NaCl/ECF vol./B.P

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8
Q

Vasopressin release is caused by 2 factors. What are these factors?

A

Osmolarity change

Baroreceptors

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9
Q

What occurs when NO vasopressin is present?

A

Dilute urine

High vol. output

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10
Q

What occurs when vasopressin IS present?

A

Concentrated urine
Low vol. output
Increased H20 reabsorption
Increased blood P

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11
Q

What is the outcome of Osmolarity change in terms of vasopressin release?

A

DEHYDRATION (neg f.b)

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12
Q

What is the outcome of Barorecpetors in terms of vasopressin release?

A

HAEMORAGE

THUS, decrease blood P (neg f.b)

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13
Q

Discuss what happens when vasopressin in present (released) in the urinary system.

A

Vasopressin binds to receptors on BASOLATERAL MEM.

ATP –> cAMP

cAMP increases luminal membranes permeability to H20 by promoting the insertion of aquaporins

Water exits through a different aquaporin on basolateral membrane and into blood.

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14
Q

Discuss the outcomes of having Diabetes Insipidus (related to Ectasy (MDMA))

A

INABILITY TO PRODUCE VASOPRESSIN

  • excessive thirst
  • excessive urine production
  • severe dehydration
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15
Q

Where is Atrial Natriuretic Peptide (ANP) released from?

A

The atria of the heart

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16
Q

Where is Brain Natriuretic Peptide (BNP) released from

A

The ventricle of the heart

17
Q

What stimulates ANP and BNP release?

A

High plasma volume detected by baroreceptors

18
Q

What is the function of ANP and BNP?

A

REDUCE B.P. IN NEPHRON
by:

  1. inhibiting Na+ reabsorption
  2. inhibiting effect of RAAS
  3. dilation of afferent arteriole

ALSO ACT ON SNS TO DECREASE CARDIAC OUTPUT

19
Q

How do ANP and BNP reduce blood P in the nephron by (1.) inhibiting Na+ reabsorption?

A
  • ANP shuts down Na+ channels on luminal mem.

- Blocks Na+ and H20 reabsorption

20
Q

How do ANP and BNP reduce blood P in the nephron by (2.) inhibiting effect of RAAS?

A
  • ANP blocks action of Aldosterone
  • Blocks Na+ channel synthesis & opening
  • Blocks Na+K+ATPase pump
  • Blocks Na+ and H20 reabsorption
21
Q

How do ANP and BNP reduce blood P in the nephron by (3.) dilating the afferent arteriole?

A
  • ANP increases GFR
  • increase glomerular capillary blood P
  • increase net filtration P
  • increase GFR
  • increase H20 excretion
22
Q

What is Hyperkalemia?

A

HIGH ECF K+

-decreases resting mem. potential
-decreases excitability by keeping voltage-gated Na+
channels CLOSED

23
Q

What is Hypokalemia?

A

LOW ECF K+

-increases resting mem. potential
-decreases excitability by increasing amount of
depolarisation required to reach threshold

24
Q

Where + what percentage does K+ reabsorption occur?

A 
PCT   (>65%)
ASCENDING LOH   (20-30%)
25
Q

Where + what percentage does K+ secretion occur?

A 
DCT
Collection Ducts   (1-80%)
26
Q

What effect does Aldosterone have on the renal handling of K+?

A

High K+ Diet –>
Increase plasma K+ –>

INCREASE ALDOSTERONE –>

Increase K+ secretion –>
Increase K+ excretion

27
Q

What effect does Aldosterone have on the renal handling of Na+?

A

Decrease ECF volume –>
Increase Renin –>
Increase Angiotensin II –>

INCREASE ALDOSTERONE –>

Increase Na+ reabsorption –>
Decrease Na+ excretion

28
Q

What effect does Aldosterone have in Cardiac Failure?

A

OVERSTIMULATION OF RAAS PATHWAY
VERY LOW BLOOD P.

Decrease plasma volume –>
[Increase SNS and Decreas GFR] (–>) Increase Renin –>
Increase Angiotensin II –>

INCREASE ALDOSTERONE –>

Increase Na+ reabsorption –>
FLUID RETENTION ODEMA

29
Q

What substance is used to prevent the overstimulation of the RAAS pathway (i.e. Cardiac Failure [low blood P])?

A

ACE inhibitors

-cause increase fluid loss by preventing salt reabsorption!

30
Q

What other factors are involved in K+ secretion?

A

Low K+ Diet
–K+ channels on luminal mem. BLOCKED

Distal capillary blood flow
–CANNOT diffuse across capillary into interstitial fluid

31
Q

What effect does haemorrhage have on K+ ?

A

INHIBITS increased K+ secretion
THUS, inhibiting K+ excretion
THUS, leading to ION CONSERVATION

Haemorrhage also ACTIVATES the RAAS pathway, also leading to ion conservation.

32
Q

What is the negative feedback loop concerning the outcome of Osmolarity change in terms of vasopressin release?

A 
Dehydration -->
Increase plasma osmolarity -->
Hypothalamic osmoreceptors stimulated -->
Increase Vasopressin secretion -->
Increase H20 reabsorption
33
Q

What is the negative feedback loop concerning the outcome of Baroreceptors in terms of vasopressin release?

A 
Haemorrhage -->
Decrease B.P. -->
Hypothalamic baroreceptors stimulated -->
Increase Vasopressin secretion -->
Increase H20 reabsorption
34
Q

What are the effects of dehydration?

A

Decrease plasma vol.
THUS, increase salt conc.
THUS, increase osmolarity

35
Q

What are the effects of increased H20 reabsorption after dehydration?

A

Increase plasma vol.
THUS, decrease salt conc.
THUS, decrease osmolarity

Completes neg. f.b. loop!

36
Q

What are the effects of haemorrhage?

A

Decrease plasma vol.
THUS, decrease stretch in vessels
THUS, increase stimulation of baroreceptors

37
Q

What are the effects of increased H20 reabsorption after haemorrhage?

A

Increase plasma vol.
THUS, increase stretch in vessels

Completes neg. f.b. loop!

Renal Physiology (5 decks)

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