Regulation of Plasma Sodium and ECF Volume (13)

Question 1

Where are the osmolarity sensors?

Where are the volume sensors?

Answer 1

Osmolarity sensors: Hypothalamus

Volume sensors: Carotid sinus, aortic arch, renal afferent arteriole, atria

Question 2

How are changes in ECF volume “sensed”?

Answer 2

Volume receptors that sense stretch

Question 3

True or False: You can consume Na+ much faster than your kidney can get rid of it.

Answer 3

True

Question 4

What is a rapid increase in body weight a measure for?

Answer 4

It is a measure of rapid increase in ECF volume (which shows an abrupt increase in NaCl)

Question 5

What is positive Na balance?

Answer 5

Not excreting as much as consuming.

It is an increase in the amount of NaCl in the ECF, resulting in an acute increase in an isosmotic expansion of the ECF volume

Question 6

What is negative Na balance?

Answer 6

Not consuming as much as excreting

Question 7

With an abrupt increase in Na consumption, what happens to plasma osmolarity and ADH levels?

Answer 7

Both increase

Question 8

What is the effective circulating volume?

Answer 8

A functional, not an anatomical, blood volume reflecting the extent of tissue/ organ where blood pressure is sensed

Question 9

True or False: The effective circulating volume normally parallels the total ECF volume

Answer 9

True

Question 10

Regulation of sodium excretion is induced by….Changes in Effective circulating volume or the total ECF volume?

Answer 10

Changes in the effective circulating volume

Question 11

When there is decreased circulating volume, what happens to renal perfusion?

Answer 11

It decreases, which leads to activation of the RAA system (which then further increases Na retention and edema)

Question 12

Which edematous disease states are associated with increased capillary hydrostatic pressure?

Answer 12

CHF, and Pulmonary edema

Question 13

Which edematous disease states are associated with decreased plasma oncotic pressure?

Answer 13

Liver disease and nephrotic syndrome

Question 14

Which is more important, low pressure sensors or high pressure sensors?

Answer 14

Low pressure sensors

Question 15

What are the systems of feedback control of effective circulating volume?

Answer 15

1. RAA hormonal system
2. Increased renal sympatheic nerve activity
3. The posterior pituitary releases ADH
4. Reduced ECF volume also decreases the release of ANP

Question 16

What is angiotensinogen?

Answer 16

Synthesized by liver and relseased into systemic circulation, it is the substrate of renin

Question 17

What is renin?

Answer 17

Synthesized and stored in granular cells of the JG apparatus of the kidney

Question 18

What is angiotensin I?

Answer 18

Substrate of ACE

Question 19

What is the action of angiotensin II?

Answer 19

1- Induces aldosterone release from adrenal cortex

2- Acts on hypothalamus to increase thirst and release ADH

3- Vasoconstricts renal and other systemic vessels

4- Enhances Na/H exhange in the proximal tubule, which increases sodium reabsorption

Question 20

What are the three renal mechanisms regulating renin release?

Answer 20

1- local real baroreceptors in afferent arterioles respond to low pressure and increase secretion of renin by granular cells

2- decreased systemic arterial blood pressure stim baroreceptor reglec which caused release of renin by JG apparatus stimulation

3- Cells of macula densa sense tubular fluid Na concentration….if low it causes the release of renin from granular/ JG cells

Question 21

What is aldosterone?

Answer 21

A mineral corticoid secreted into circulation by the adrenal cortex

Question 22

What is the primary long term regulator of salt balance and extracellular fluid volume and therefore BP?

Answer 22

Aldosterone

Question 23

What does aldosterone do to the kidney tubules?

Answer 23

Increases the reabsorption of Na and increases the secretion and excretion of K+

Question 24

Which cells does aldosterone act on?

Answer 24

Principal cells in the distal tubule and early collecting duct of the renal cortex

Question 25

How does aldosterone increase Na reabsorption?

Answer 25

Increased basolateral membrane Na/K pumps Increased apical Na channels Increased mitochondrial enzymes (ATP)

Question 26

True or False: Soulte reabsorption in cortical nephron segments participates in the counter current multiplication of the corticomedullary solute concentration gradient

Answer 26

False...it is actually rapidly returned to the general circulation and DOES NOT participate in the counter current multiplication of the cortico-medullary solute concentration gradient

Question 27

WHen in Na balance, what percentage of filtered Na is excreted?

Answer 27

0.4%

Question 28

Can sodium be secreted?

Answer 28

No...only filtered and reabsorbed (and then excreted)

Question 29

Where is the majority of Na reabsorbed?

Answer 29

The proximal tubule

Question 30

In the distal tubule/ collecting duct, what is Na reabsorption coupled to?

Answer 30

The secretion of K+

Question 31

What is hypernatremia?

Answer 31

An increase in plasma sodium concentration to a level above normal range

Question 32

What is normal sodium range?

Answer 32

135-145 mEq/L

Question 33

What are the symptoms of hypernatremia?

Answer 33

Lethargy, weakness and irritability

Question 34

What are the severe symptoms of hypernatremia and when is it seen?

Answer 34

Seizures and coma may occur at levels above 158 mEq/L

Question 35

In general, what is hypernatremia caused by?

Answer 35

A loss of water in excess of solutes from th eplasma due to inadequate consumption of water in excess of solute and/ or An inappropriate renal excretion of water in exces of solute

Question 36

The following are causes of what condition? Inadequate water consumption Extreme sweating Severe diarrhea Excessive renal excretion of water (polyuria)

Answer 36

Hypovolemia Hypernatremia

Question 37

What two medical conditions are associated with excessive renal excretion of water?

Answer 37

Diabetes mellitus and diabetes insipidis

Question 38

In central diabetes insipidus, what is the cause of polyuria?

Answer 38

Inadequate release of ADH from the posterior pituitary in response to an increase in plasma osmolariy

Question 39

What is the cause of polyuria in nephrogenic diabetes insipidus?

Answer 39

An inability of the collecting tubule and collecting duct to respond to ADN by increasing water permeability despite adequate release of ADH in response to increased plasma osmolarity

Question 40

What are the causes of hypervolemic hypernatremia?

Answer 40

Excessive hypertonic fluid consumption (seawater) IV infusion of hypertonic saline Hyperaldosteronism

Question 41

What is hyponatremia?

Answer 41

Decrease in sodium concentration to a level below the normal range

Question 42

What are the symptoms of hyponatremia?

Answer 42

Nausea, vomiting, headache, lethargy, fatigue, loss of appetite, restlessness and irritability, muscle weakness, spasms or cramps

Question 43

What are the symptoms of severe hyponatremia and what level are they seen at?

Answer 43

Neuro deficits, brain swelling, seizures, coma Na levels below 125 mEq/L

Question 44

In general, what is the cause of hyponatremia?

Answer 44

Caused by a gain of water in excess of solutes in the plasma due to: An extreme, excess consumption of water and an inappropriate increase in "free water" reabsorbed by the kidney

Question 45

What are the causes of hypervolemic hyponatremia?

Answer 45

In appropriate reab or water in excess of solutes from the tubular fluid to the plasma effectively increases plasma volume and dilutes plasma Na

Question 46

What are some diseases associated with hypervolemic hyponatremia?

Answer 46

CHF, kidney failure, liver failure, Syndrome of Inappropriate Anti-Diuretic Hormone, Polydispia

Question 47

What are some causes of hypovolemic hyponatremia?

Answer 47

May occur in a clinical setting where plasma volume reduction is extreme where consumption of water as well as increased "water in excess of solute" reabsorption by the kidney is insufficient to correct volume depletion by is sufficient to decreases plasma Na

Question 48

What clinical conditions are associated with hypovolemic hyponatremia?

Answer 48

Addison's disease (adrenal insifficiency) Severe vomiting or diarrhea