Crr Week 3: Regulation Of Sodium Balance

Front 1

What kind of sensors/receptors detect changes in sodium balance?

Where are they located?

Back 1

Baroreceptors (volume-dependent receptors)

*Afferent arterioles, carotid sinus, aortic arch, and right atria

Front 2

List 4 major effectors of the volume regulatory pathway.

Back 2

1. Renin-angiotensin-aldosterone
2. Atrial natriuretic peptide
3. ADH
4. Norepinephrine

Front 3

Which portion of the extracellular fluid compartment is sensed by the baroreceptors?

Back 3

Plasma volume
(effective circulating volume)

Front 4

How does GFR affect sodium excretion?

Back 4

Increases in GFR increase sodium excretion, decreases in GFR decrease sodium excretion

Front 5

What is direct the function of Angiotensin II on the nephron?

Back 5

Stimulates the Na+-H+ exhcanger in the proximal tubule
(increases sodium reabsorption)

Front 6

Which substances stimulate the Na+-H+-exchanger in the proximal tubule?

Back 6

1. Angiotensin II
2. Norepinephrine

Front 7

What is the most important site on the nephron for the regulation of sodium reabsorption?

Back 7

Distal tubule and collecting duct

Front 8

What are the actions of aldosterone on the nephron?

Back 8

1. Increases tubular reabsorption of Na+ by principal cells in cortical collecting ducts

2. Stimulates proton secretion by intercalated cells in the outer medullary sections of the collecting tubule.

Front 9

Does the loss of aldosterone decrease plasma concentration of Na+?

Back 9

No
Loss of sodium will be accompanied by loss of osmotically-obligated water in the urine, so the concentration will not be changed

Front 10

List 4 factors that stimulate aldosterone release.

Back 10

1. Decreased ECF volume (low Na+ diet)
2. Increased plasma K+ concentration
3. Increased plasma angiotensin II concentration
4. ACTH

Front 11

What is the most important regulation system for Na+ reabsorption?

What is the rate-limiting step?

Back 11

Renin-angiotensin-aldosterone system

Renin release is the rate-limiting step

Front 12

List 3 controls for renin release

Back 12

1. Extrarenal baroreceptors (carotid sinus) + intrarenal baroreceptors (afferent arterioles)
2. Macula densa mechanism
3. Sympathetic nerve activity

Front 13

What is the initial stimulus for the renin-angiotensin-aldosterone system?

Back 13

Decreased plasma volume
(sensed by carotid sinus and afferent arteriole baroreceptors, and macula densa cells)

Front 14

List 2 ways that angiotensin II decreases sodium excretion.

Back 14

1. Decreasing Na+ filtration (decreased GFR)
2. Increasing Na+ reabsorption in proximal and distal nephron

Front 15

Sympathetic nerve activity increases Na+ reabsorption through actions on which parts of the nephron?

Back 15

1. Afferent and efferent arterioles
2. Juxtaglomerular cells (secrete renin)
3. Proximal tubule cells

Front 16

Which hormone functions in the "Na+ losing" system?

Back 16

Atrial Natriuretic Peptide

Front 17

Does Norepinephrine participate in the Na+-conserving or Na+-losing system?

Back 17

Na+-conserving system

Front 18

What is the effect of Norepinephrine on GFR and RPF?

Back 18

Both are decreased
(due to vasoconstriction)

Front 19

What is the effect of ANP on GFR and RPF?

Back 19

Both are increased
(due to vasodilation)

Front 20

Is proximal reabsorption increased or decreased with Norepinephrine?

Back 20

INCREASED
(NE stimulates Na+-H+ exchanger, and increases the filtration rate, resulting in a greater peritubular reabsorptive force)

Front 21

What is the effect of Angiotensin on proximal reabsorption?

Back 21

Proximal reabsorption is INCREASED
(AGII stimulates Na+-H+ exchanger, and increases the filtration rate, resulting in a greater peritubular reabsorptive force)

Front 22

What is the effect of Aldosterone on distal reabsorption?

Back 22

INCREASED reabsorption

Front 23

What is the effect of ANP on proximal reabsorption?

Back 23

DECREASED reabsorption
(due to vasodilation, which leads to less peritubular reabsorptive force-- diluted osmotic gradient)

Front 24

What is the effect of ANP on distal reabsorption?

Back 24

DECREASED reabsorption
(inhibits Na+ diffusion in collecting duct)

Front 25

Is medullary blood flow increased or decreased in Na+-conserving systems?

Back 25

Decreased
(better gradient, more water reabsorbed)

Front 26

Does ANP increase or decrease medullary blood flow?

Back 26

Increase

Front 27

List 2 ways the water retention occurs.

Back 27

1. Disinhibition of left atrial baroreceptors, enhancing ADH release
2. Stimulatory effects of sympathetic activity and angiotensin II on ADH release and thirst

Front 28

For osmoregulation, what is sensed?
What are the sensors and effectors?

Back 28

Plasma osmolality is sensed
Sensors: hypothalamic osmoreceptors
Effectors: ADH and thirst

Front 29

For volume regulation (sodium balance) what is sensed?
What are the sensors and effectors?

Back 29

Effective tissue perfusion is sensed
Sensors: afferent arteriole, atria, carotid sinus
Effectors:
1. Renin-angiotensin-aldosterone
2. ADH
3. ANP
4. Norepinephrine

Front 30

What is the effective arterial blood volume (EABV)?

Back 30

Portion of the ECF volume in the blood that is "effectively" perfusing the tissues.

Front 31

With edema, do both the ECF volume and effective arterial blood volume increase?

Back 31

NO.
ECF volume increases, EABV decreases (due to excessive filtration of fluid out of the capillaries into the interstitial fluid)