Regulation of EC fluid volume and NaCl balance

Question 1

Effects of hypovolemia

Answer 1

Dizziness and fainting (syncope)
Dry nose
Muscle weakness
Decreased blood pressure

Question 2

Effects of hypervolemia

Answer 2

Stroke, headache, and vision loss
Heart attack
Renal failure
Increased BP and CVP
Pitting edema

Question 3

Management of high BP

Answer 3

targets renal handling of NaCl

Question 4

Water balance regulation

Answer 4

IN: food, water, metabolism
OUT: sweat, poo, pee, exhalation

Question 5

Hyperthermia

Answer 5

Too much water loss via sweating, causes urination and defecation water loss to decrease

Question 6

Measuring salt content

Answer 6

High and low pressure cardiovascular stretch receptors

Question 7

High pressure receptors

Answer 7

located in afferent arterioles of kidney
–responds by regulating Na balance
located carotid sinus, and aortic arch.
–these respond to changes in sympathetic tone, mainly involve responses concerning the heart
If arterial pressure establishes a higher norm, so will rate of carotid discharge

Question 8

Low pressure receptors

Answer 8

located in cardiac atria, large veins, larrge pumonary vessels, liver, and ventricles

• Atria secrete ANP
• others change sympathetic tone (even renal)

Question 9

Renal Sympathetic Nerves

Answer 9

Increase renin secretion
Increase Na reabsorption in proximal tubule
Increase Afferent tone which decreases GFR
(all of this to increase ECV/BP)

Question 10

Na resorption in proximal tubule

Answer 10

Na resorption in proximal tubule happens via Na/H+ exchanger on lumen side. Norepinephrine and AG2 increase Na resorption and therefore also H+ secretion

Question 11

Regulation of renin release

Answer 11

Low pressure at afferent arteriole increases renin release
B-adrenergic sympathetic tone increases renin release
Increased Na load at macula densa decreases renin release
Increased levels of pressor hormones (like Ag2) increase renin release
ANP decreases it

Question 12

Aldosterone

Answer 12

-Acts on distal tubule
Steroid hormone, effects are mediated by MR receptor in inside the cell. MR also has affinity of cortisol, so aldosterone target cells inactivate cortisol
-Aldosterone increases Na resorption (which kind of increases K secretion)
-Increases acid secretion

Question 13

Effect of low sodium

Answer 13

When sodium intake is low, AG2 and sympathetic stimulation increase resorption in proximal tubule, and overall percentage excreted is reduced.

Question 14

Autoregulation

Answer 14

GFR and RBF are autoregulated from 80-180 mmhg, but Na excretion is not and increases exponentially

Question 15

Secretion Vs Filtration

Answer 15

Other than aldosterone, all regulators of Na excretion are vasoactive and regulate Na excretion by altering tubular resorption rather than filtration

Question 16

Locus of Na resorbtion

Answer 16

Although 95% of Na is resorbed in proximal tubule and LH, resorption in distal tubule and collecting ducts are most important for regulation