Regulation of ECF Volume and NaCl Balance

Question 1

• High ADH can do what to sodium levels?

Answer 1

Can cause hyponatremia

Question 2

• When ADH is always high, _ is no longer controlled by ADH
• _ is then controlled by amount of free water you take in

Answer 2

Sodium

Sodium

Question 3

Urine should be _ in hyponatremia

Answer 3

diluted

Question 4

• How do you distinguish if the kidneys are responding appropriately to hyponatremia?**

Answer 4

• Urine is diluted
  
  • Kidneys are responding appropriately
  • ADH levels are low (where they should be)
  • Problem is outside of the kidneys

Question 5

• Maintaining _ balance is important for long-term regulation of ECF volume
• Maintaining _ balance is important for regulating ECF osmolarity

Answer 5

Salt

Water

Question 6

• ECV (Effective Circulating Volume)

Answer 6

• Portion of the ECG volume that is in the arterial system ubder particular pressure and is effectively perfusing the tissues
• Not a measurable and distinct body fluid compartment

Question 7

How much of the vascular volume forms the ECV?

Answer 7

• 0.7 L (20% plasma, 5% of ECF, 1.7% TBW, 1% of body weight)

Question 8

• How is effective circulative volume changed in a person with congestive heart failure?
• How is this counteracted

Answer 8

• CHF patients have a low effective circulating volume (d/t decreased cardiac output)
• 4 Ways this is counteracted
• 1) Activation of RAAS system
• 2) Stimulation of sympathtetic nervous system via baroreceptor reflex
• 3) Increased ADH​ secretion
• 4) Increaed renal fluid retention via altered Starling’s forces in the peritubular capillaries

Question 9

• How is ECF volume changed in a person with CHF?

Answer 9

• Increased (Na+ and fluid retention-edema)

Question 10

• Where are osmoreceptors located?
• What do they respond to?
• How do they respond?

He included this twice, so probably will be on the test

Answer 10

• Supraoptic and paraventricular areas of the hypothalamus
• Changes in plasma osmolarity
• Respond in two ways:
  
  • Regulate ADH release
  • Regulate thirst

Question 11

• ADH secretion is controlled by what two receptors?
• Which is more sensitive?

Answer 11

• Osmoreceptors, barorecceptors
• Osmoreceptors

Question 12

Most important non-osmotic stimulus of ADH release

Answer 12

Decrease in sensed body volume/Decline in blood pressure (20% or greater)

Question 13

• With volume expansion, secretion of ADH is _
• With volume contraction, secretion of ADH is _

Answer 13

• Decreased
• Increased

Question 14

• _ baroreceptors have an important influence on the hypothalamus and secretion of ADH
• _ baroreceptors have major role in RAAS pathway

Answer 14

• Cardiopulmonary (in cardiac atria and pulmonary arteries)
• Intrarenal

Question 15

Identify the following types of baroreceptors

Answer 15

• Arterial
• Cardiopulmonary
• Intrarenal

Question 16

• Problems with Na+ balance manifest as altered _
• What senses this?
• What is the effector?
• What is affected a a result?

Answer 16

• ECF volume
• Arterial and cardiac baroreceptors
• Angiotensin II, Aldosterone, SNS, ANP
• Urine Na+ excretion

Question 17

• Problems with _ balance manifest as altered plasma osmolality, which is reflected in an alteration in plasma _
• What is sensed?
• What is the sensor?
• What is the affector?
• What is the effect?

Answer 17

• Water, Na+
• Changes in plasma osmolality
• Hypothalamic osmoreceptors
• AVP/ADH
• Urine osmolality (H20 output) and thirst

Question 18

• Decrease in total body Na+ content leads to eventual ECF _
• Increase in total body Na+ content leads to eventual ECF _

Answer 18

• Contraction
• Expansion

Question 19

• How do the renal sympathetic nerves act as volume sensors?
• What actions do they perform?

Answer 19

• Respond to changes in ECFV delivery to kidney
• In the event of low ECFV:
  
  • Decrease GFR
  • Increase Renin Secretion
  • Increase Na+ reabsorption along the nephron

Question 20

• How does the RAAS system respond to changes in ECFV?

Answer 20

• In the event of low NaCl and water delivery to the kidney
• Increase of angiotensin II to stimulate Na+ reabsorption along neprhon
• Aldosterone stimulates Na+ reabsorption in the distal tubule and collecting duct (and to a lesser extent in the ascending LOH)
• Increased angiotensin II stimulates secretion of ADH
• ADH increases water reabsorption in the collecting duct

Question 21

• How do naturiretic peptides (ANP, BNP, Urodilatin) respond to changes in ECFV?

Answer 21

• Increased secretion leads to increased NaCl excretion
• • Increase in GFR
• Decrease in renin secretion
• Decreased aldosterone secretion (indirect via angiotensin II and direct on adrenal gland)
• Decrease NaCl and water reabsorption by the collecting duct
• Decrease ADH secretion

Question 22

• How does AVP/ADH respond to changes in ECFV?

Answer 22

• Increases H2O reabsorption by the distal tubule and collecting duct

Question 23

• 3 mechanisms for the regulation of renin release

Answer 23

1. Perfusion pressure
   
   1. Low perfusion pressure in afferent arterioles stimulates renin secretion
   2. High perfusion pressure in afferent arterioles inhibits renin secretion
2. Sympathetic nerve activity
   
   1. Activation of sympathetic nerve fibers in afferent arterioles increases renin secretion
3. NaCl Delivery to the macula densa (tubuloglomerular feedback)
   
   1. When NaCl delivery to the macula densa is decreased, renin secretion is stimulated

Question 24

• Renin is responsible for catalyzing which reaction?

Answer 24

• Conversion of angiotensinogen to angiotensin I

Question 25

• Where is ANP produced?
• When is ANP released?
• What are the effects of ANP?

Answer 25

• Atrial cardiac muscle cells
• ECF volume is increased and receptors are stretched in muscle cells
• Directly inhibit Na+ reabsorption in the distal parts of the nephron (increasing Na+ excretion and accompanying osmotic H2O excretion in the urine)
• Also increases Na+ excretion by inhibiting RAAS
  
  • Inhibits renin secretion by the kidneys and acts on adrenal cortex to inhibit aldosterone secretion
  • Inhibits secretion and action of vasopressin

Question 26

• What happens to Na+ with volume expansion?

Answer 26

• Decreased activity of renal sympathetic nerves
• Increased release of ANP and BNP from the heart and urodilatin from the kidneys
• Inhibition of ADH/AVP secretion from posterior pituitary and decreased ADH action on the collecting duct
• Decreased renin secretion and thus decreased production of angiotensin II
• Decreased aldosterone secretion
• OVERALL INCREASE IN NA+ AND H2O EXCRETION

Question 27

• What happens to Na+ with volume contraction?

Answer 27

• Sodium is reabsorbed
• Increase in sympathetic nerve activity in the kidney
• Increased secretion of renin, angiotensin and aldosterone
• Stimulation of ADH secretion by the posterior pituitary
• NET EFFECT IS LESS Na+ and H2O SECRETION AND MORE REABSORPTION

Question 28

• Hyponatremia
  
  • Serum Na+ levels
  • Serum Osmolality
• What types of fluid shifts will occur

Answer 28

• Serum Na+ < 135 mEq/L and serum osmolarity <280 mOsm/kg
• Since serum Na+ levels are decreased, more water will shift from the ECF to the ICF and can cause cerebral edema and hypovolemia

Question 29

• Mechanisms for regulating ECF volume
• Outcomes if the variable is not normal

Answer 29

• Maintenance of salt balance; accomplished by aldosterone controlled adjustments of Na+ excretion in the urine
• If salt balance is not properly regulated
• Decrease in ECF volume leads to a decrease in arterial BP
• Increase in ECF volume leads to an increased in arterial BP

Question 30

• What are the mechanisms for regulating ECF osmolarity?
• What happens if osmolarity is not normal?

Answer 30

• H2O balance; Vasopressin controlled adjustments in the excretion of H2O in the urine
• If there is an increase in ECF osmolarity, fluid will leave cells and cells will shrink
• If there is a decrease in ECF osmolarity, fluid will shift into the cells and the cells will swell