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Physiology > Regulation Of ECF Volume > Flashcards

Regulation Of ECF Volume Flashcards

1
Q

What happens when there is a Net increase in Total Body Na+? A Net decrease in Total Body Na+?

A

Increase Net Na+: Increased Osmolarity, and Body Fluid volume
Decreased Net Na+: Decreased Osmo. And Body Fluid Volume

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2
Q

How do kidneys Regulate Total Body Na+?

A

Via Excretion of Na+:

Excretion = (GFR x Plasma [Na+]) - Na+ Reabsorbed

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3
Q

What are the 3 ways to adjust Na+ Excretion?

A

1) Control Plasma Na+ (Eating and Drinking)
2) change in GFR
3) change in Na+ Reabsorption

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4
Q

What are some Factors that control GFR?

A 
Renal Sympathetic Nerves 
Renin-Angiotensin System 
Prostaglandins 
Glomerular Tubular Balance 
Autoregulation: Tubular Glomerular Feedback Mechanism
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5
Q

What are the sensors that can detect Changes in Na+ Balance?

A

Extrarenal Baroreceptors: Carotid sinuses, arteries, cardiac chambers and great veins

Intrarenal Baroreceptors: Renal Juxtaglomerular Apparatus and Macula Densa Cells that control Renin Secretion

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6
Q

How do Renal Sympathetic Nerves control GFR?

A

Increased Nerve Activation Causes:

Increased Constriction –> Decreased Pgc –> Decreased Renal BF -> Deceased GFR

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7
Q

How does the Renin Angiotensin System Control GFR?

A

Increased Renin Release Causes:

Increased Plasma Ang II –> Decreased Renal BF –> Decreased GFR

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8
Q

How do Prostaglandins Control GFR?

A

Prostaglandins such as: Prostacyclin, are vasodilator a that prevent platelet aggregation and Increase GFR.

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9
Q

How does Glomerular Tubular Balance Control GFR?

A

1) Under normal conditions GTB allows for 60-65% Na+ Reabsorption
2) If there is an increase in GFR, there will be an increase in Glucose and Increase in a.a. Filtration which increases Na+ Reabsorption.

This balance is important to maintain proper Na+ balance in the event of GFR changes.

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10
Q

How does Autoregulation: Tubular Glomerular Feedback Mechanism Control GFR?

A

Autoregulation allows GFR to remain relatively constant over a wide range of Perfusion pressures (systemic pressure)

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11
Q

What Controls Na+ Reabsorption?

A 
Aldosterone 
Renal Sympathetic Nerves
Angiotensin II 
Atrial Natriuretic Peptide (ANP) 
Antidiuretic Hormone (ADH)
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12
Q

What is Aldosterone?

A

It is a hormone that is secreted by the Adrenal Cortex (Zona Glomerulosa)

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13
Q

What stimulates The Adrenal Cortex and Aldosterone Secretion?

A

1) Increased Adrenocorticotropic Hormone (ACTH)
2) Increased Plasma K+
3) Increased Angiotensin II (due to stimulated Renin:low volume and low Na+)

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14
Q

What is the Function of Aldosterone?

A

1) It increases the # of Na+ channels in Lumen (collecting ducts)
2) Increases # of Na+/K+ pumps in Basolateral membrane (Collecting Ducts)
3) Increases ATP generation

All of these lead to Na+ Reabsorption

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15
Q

How Do Renal Sympathetic Nerves Control Na+ Reabsorption?

A

A) Via Alpha Adrenergic Receptors:
- Which Cause Vasoconstriction of Aff and Eff Arterioles
- Altering Starling Forces and FF (increased oncotic and decreased hydrostatic in PTC)
B) Via Beta Adrenergic Receptors:
- Stimulation of B Receptors in Granular Cells –> Renin Secretion –> DIRECT stimulation of Na+ Reabsorption in Prox. Tubules

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16
Q

How Does Ang II effect Na+ Reabsorption in Proximal Tubules?

A

1) DIRECT EFFECTS:
- Stimulates Na+/H+ exchanger in Proximal Tubules & Na+ Reabsorption
- Increased FF & Na+ Reabsorption in Prox Tubules
2) INDIRECT EFFECTS:
- Increased Aldosterone Secretion

17
Q

How does Atrial Natriuretic Peptide (ANP) control Na+ Reabsorption?

A
  • Atrial cells secrete ANP due to high volume stretching
    1) ANP Inhibits Na+ Reabsorption in the Collecting Ducts by
    2) Increasing cGMP
    3) Vasodilator of Renal Arterioles
    4) Inhibits Renin Secretion
18
Q

How does Antidiuretic Hormone (ADH) control Na+ Reabsorption?

A

ADH only has a MINOR effect on Na+ Reabsorpton

It Increases Na+ Reabsorption in Thick ALoH, Distal Tubules, and Collecting Duct

19
Q

What is the MAJOR control Factor of Water Excretion?

A

The RATE of Water Reabsorption, which is determined by ADH levels

20
Q

What is the MAJOR function of Antidiuretic Hormones (ADH)?

A

The MAJOR function is to Increase Permeability of the Cortical and Medullary Collecting Ducts to Water and Decrease Water Excretion.

21
Q

What Controls Antidiuretic Hormone (ADH) secretion?

A

Baroreceptors and Osmoreceptors.

22
Q

How do Baroreceptors Control ADH secretion?

A

Baroreceptors Detect Stretch, which is mediated by volume and Pressure.

HEMORRHAGE:
Decreased Cardiovascular pressure –> Decreased Baroreceptor Firing –> Increased ADH secretion –> Collecting Duct Permeability –> Increased H20 Reabs and Decreased H20 excretion.

**This Process helps to restore ECF volume via Increased H2O Reabsorption and increased BP **

23
Q

The Regulation of Na+ is directly tied to what?

A

Maintenance of Body Fluid Volume.

24
Q

How do Osmoreceptors Control ADH secretion?

A

Osmoreceptors react to changes in Osmolarity.
A) Thirst Response (high Osmo)
Decreased Blood Vol. –> Incr. ADH secret –> Incr Collecting Duct perm. To H2O –> incr.H2O reabs and thirst response

B) Excess H2O Ingested (low Osmo)
High [H2O] –> Decr ADH secret –> Decr Collecting Duct Perm. To H2O –> decr H2O reabs –> Incr H2O excretion

25
Q

What controls Na+/H2O Reabsorption/Excretion During Euvolumia?

A

Euvolumia (Normal ECF volume)

  1. Proximal Tubules and LoH: Reabs 90% of Na+, and the other 10% gets deliver to distal tubules
  2. Distal Tubules and Collecting Ducts: Reabsorbed Na+ will be regulated so that Na+ excreted = Na+ ingested
26
Q

What mechanisms constantly make sure that Na+ gets delivered to Distal Tubules?

A 
Autoregulation 
Glomerular Tubular Balance 
Sympathetic Nerve Activation 
Angiotensin II 
Metabolites( Prostaglandins, NO-, Dopamine)
27
Q

What hormones Regulate Na+ Reabsorption in the Distal Tubules and Collecting Duct?

A 
Aldosterone 
Atrial Natriuretic Peptide (ANP) ( vasodilator) 
Antidiuretic Hormone (ADH) (minor fun)
28
Q

How is Na+/H2O Reabsorption/Excretion Regulated during ECF Contraction?

A

Isovolumic Contraction occurs during: Diarrhea or Hemorrage.

  1. A decrease in H2O and Na+ happens first
  2. Decr Plasma Volume and Increase Arterial Oncotic Press
  3. A series of events occurs that effect ( systemic pressure, Renal symp nerves, Renin, Ang II, and Constriction occurs)
  4. Leading to Decr GFR
  5. **Ultimately leading to Decreased Na+ and H2O excretion and Increased Na+ and H2O Reabsorption **
29
Q

What causes ECF Expansion?

A
  1. Congestive Heart Failure

2. Primary Hyperaldosteronism

30
Q

How does Congestive Heart Failure controls Na+/H2O during ECF Expansion?

A

During Congestive Heart Failure, Neurohumoral Compensatory Mechanisms Activate to Increase Na+ and H2O Retention and Edema .

  1. Increased Sym. Nerve Stimulation
  2. Increased Renin-Angiotensin system
  3. Increased ADH release
  4. Increased Aldosterone release
  5. Increased Na+ and H2O retention
31
Q

What stimulates the sympathetic Nervous System?

A

Low CO
Failing Heart
Low Volume in Arterial System
Low Perfusion Pressures –> Renin release

32
Q

How does Primary Hyperaldosteronism cause ECF expansion, and how is Na+/H2O regulated?

A

Hyperaldosteronism - is the over secretion of Aldosterone.

  • W/ the increased level of Aldosterone, there is an Initial increase Na+, but then a couple days later, that Na+ is excreted and Na+ levels return to normal despite the continued presence of Aldosterone.
  • The change in [Na+] “escapes” because there is an Increase in ECF, Increased GFR, Decreased Renal Symp. Nerve Activity, and Decreased Ang II
33
Q

What causes Hypernatremia?

A

A. Central Diabetes Insipidus - which is a decrease in ADH release in the pituitary gland, which causes an increase in H2O excretion in the urine.

B. Nephron enact Diabetes Insipidus - which is when you have Normal levels of ADH, but the Tubules don’t respond to circulating ADH, and there is an increased H2O excretion in the urine.

34
Q

What is the function of the Neurohumoral Compensatory Pathway?

A

It “overrides” the Autoregulatory Mechanisms during extreme situations such as Diarrhea or Hemorrhage. It causes Na+ and H2O retention and exacerbates Edema

Physiology (9 decks)

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