Hormonal Regulation of Salts

Question 1

How do the kidneys keep the ECF volume constant?

Answer 1

They match the excretion of NaCl to the ingested NaCl.

Question 2

What are positive and negative Na balances?

Answer 2

Positive Na Balance - intake > excretion

Negative Na Balance - excretion > intake

Question 3

What does the Na+ balance affect in the ECF?

Answer 3

It affects the volume of the ECF but not the [Na+]

Question 4

How does an increase in Na+ affect the ECF?

Answer 4

It will increase the ECF’s volume

Question 5

What is the effective circulating volume (ECV) and how is it different from the ECF?

Answer 5

ECV is the portion of the ECF that is in the circulatory system and is perfusing tissues.

Question 6

What is ECV related to?

Answer 6

Arterial Pressure

Cardiac Output

Question 7

What is the effect of decreased ECF on ECV?

Answer 7

Decreased ECF will lower blood volume, BP or cardiac output and the ECV will decrease.

Question 8

What is the effect of increased ECF on ECV?

Answer 8

It will increase blood volume, BP or cardiac output and the ECV will increase

Question 9

Can the ECF and ECV vary independently?

Answer 9

They can in some diseases such as:

congestive heart failure
hepatic cirrhosis
pleural effusion

Question 10

What happens with a trigger of the atrial stretch receptors?

Answer 10

Atrial Natriuretic Peptide would be released which leads to the increased excretion of Na and water.

Question 11

What happens with pulmonary vascular engorgement?

Answer 11

The sympathetics would become less active and ADH would be decreased leading to diuresis and increased urine output.

Question 12

What happens with increased stimulation of the aortic and carotid baroreceptors?

Answer 12

Sympathetic nerve activity will decrease and ADH will decrease. This leads to increased urine flow and diuresis.

Question 13

What happens when tubular flow becomes very slow?

Answer 13

The juxtaglomerular apparatus is stimulated and renin is increased which leads to increased aldosterone and will increase the reabsorption of water and Na.

Question 14

What happens with increased liver pressure?

Answer 14

Decreased sympathetic activity leading to decreased ADH and increased Na excretion

Question 15

What happens with increased portal vein Na sensors?

Answer 15

Decreased sympathetic activity leading to decreased ADH and increased Na excretion

Question 16

What happens with increased [Na] in the carotid artery and the CSF?

Answer 16

Sympathetic activity will be decreased and Na excretion will increase.

Question 17

What is the effect of increased renal sympathetic nerves?

Answer 17

This occurs as a response to decreased GFR.

Renin secretion will increase which will lead to increased Na reabsorption along the nephron.

Question 18

What is the effect of increased Renin-Angiotensin-Aldosterone activity?

Answer 18

Increases in AT-II will stimulate reabsorption of Na along the nephron and it will stimulate secretion of ADH.

Increases in aldosterone will stimulate Na reabsorption in the thick ascending limb, distal tubule and the collecting duct.

-> Salt Retention

Question 19

What happens with increased ANP secretion?

Answer 19

This occurs as a response to increased GFR.

It will decrease renin secretion and aldosterone secretion. This leads to decreased water and Na reabsorption by the CD and the ADH secretion will be decreased as well.

-> Salt Excretion

Question 20

What happens with increased ADH secretion?

Answer 20

Leads to increased H2O reabsorption in the distal tubule and the collecting duct.

Question 21

What are the 3 factors that are important in renin secretion?

Answer 21

• Perfusion pressure of the afferent arteriole which acts like a baroreceptor
• Sympathetic nerve activity will activate renin secretion
• NaCl delivery to the macula densa via TG feedback where if there is decrease NaCl to the macula densa then the renin secretion will increase

Question 22

What is the negative feedback loop concerning the macula densa?

Answer 22

As ECV decreases, BP will decrease and so sympathetics will increase leading to decreased renal perfusion and decreased GFR to the macula densa which will increase the renin secretion and raise the ECV.

Question 23

What is the pathway of renin?

Answer 23

Renin activates angiotensinogen into AT-I
AT-I -> AT-II in the lung via ACE
AT-II stimulates ADH release and aldosterone production
Aldosterone increases the number of Na-K ATPase pumps which leads to increase Na and H2O reabsorption

Question 24

What is the effect of ANP on sympathetics?

Answer 24

It will decrease sympathetic activity which will decrease ADH and increase GFR.

Decreased ADH will lead to water diuresis.
Increased GFR will lead to increased Na excretion

Question 25

What is the effect of ANP on aldosterone?

Answer 25

It will decrease aldosterone and lead to decreased Na reabsorption

Question 26

What is the effect on ANP on renin?

Answer 26

It will decrease renin and lead to decreased Na reabsorption

Question 27

What is glomerulotubular balance?

Answer 27

In the PT Na reabsorbed load is proportional to the filtered load

Question 28

Describe the reabsorption of Na in the TAL. What is it proportional to?

Answer 28

Na reabsorption in the TAL is proportional to the Na delivery rate

Question 29

What is Na reabsorption in the DT and CD stimulated by?

Answer 29

Increased Na loads

Question 30

What are the 3 main responses to increased ECV?

Answer 30

Increased GFR
Decreased Na reabsorption in the PT
Decreased Na reabsorption in the CD

Question 31

What are the 3 main responses to decreased ECV

Answer 31

Decreased GFR
Increased Na reabsorption in the PT
Increased Na reabsorption in the CD