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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
Where + what percentage does K+ secretion occur?
``` DCT Collection Ducts (1-80%) ```
26
What effect does Aldosterone have on the renal handling of K+?
High K+ Diet --> Increase plasma K+ --> INCREASE ALDOSTERONE --> Increase K+ secretion --> Increase K+ excretion
27
What effect does Aldosterone have on the renal handling of Na+?
Decrease ECF volume --> Increase Renin --> Increase Angiotensin II --> INCREASE ALDOSTERONE --> Increase Na+ reabsorption --> Decrease Na+ excretion
28
What effect does Aldosterone have in Cardiac Failure?
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
What substance is used to prevent the overstimulation of the RAAS pathway (i.e. Cardiac Failure [low blood P])?
ACE inhibitors -cause increase fluid loss by preventing salt reabsorption!
30
What other factors are involved in K+ secretion?
Low K+ Diet --K+ channels on luminal mem. BLOCKED Distal capillary blood flow --CANNOT diffuse across capillary into interstitial fluid
31
What effect does haemorrhage have on K+ ?
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
What is the negative feedback loop concerning the outcome of Osmolarity change in terms of vasopressin release?
``` Dehydration --> Increase plasma osmolarity --> Hypothalamic osmoreceptors stimulated --> Increase Vasopressin secretion --> Increase H20 reabsorption ```
33
What is the negative feedback loop concerning the outcome of Baroreceptors in terms of vasopressin release?
``` Haemorrhage --> Decrease B.P. --> Hypothalamic baroreceptors stimulated --> Increase Vasopressin secretion --> Increase H20 reabsorption ```
34
What are the effects of dehydration?
Decrease plasma vol. THUS, increase salt conc. THUS, increase osmolarity
35
What are the effects of increased H20 reabsorption after dehydration?
Increase plasma vol. THUS, decrease salt conc. THUS, decrease osmolarity Completes neg. f.b. loop!
36
What are the effects of haemorrhage?
Decrease plasma vol. THUS, decrease stretch in vessels THUS, increase stimulation of baroreceptors
37
What are the effects of increased H20 reabsorption after haemorrhage?
Increase plasma vol. THUS, increase stretch in vessels Completes neg. f.b. loop!

Renal Physiology (5 decks)

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