Exam 4: Fluid Balance 191 - 196

Question 1

Typical fluid input per day is how much

Answer 1

2.5 liters/day

Question 2

Fluid input/water sources comes from what every day?

Answer 2

Drink - 50%
Food - 35%
Oxidation - 15%

Question 3

Typical fluid output is about how much?

Answer 3

Matching! 2.5 liters/day

Note: output is controlled by the kidneys.

Question 4

Fluid output breakdown by %:

Answer 4

Urine = 60%
Sweat & ventilation = 35%
Stool/feces = 5%

Question 5

In a lab, a group of students drink a liter of distilled water (pure H2O). What do you expect their urine concentration to be?

Answer 5

Larger volume of dilute urine

Question 6

In a lab, a group of students drink a liter of an iso-tonic solution (like body fluids - 0.9% NaCl). What do you expect their urine concentration to be?

Answer 6

Balanced, iso-tonic urine

Question 7

In a lab, a group of students drink 1/4 liter of ~10% salt solution (NaCl). What do you expect their urine concentration to be?

Answer 7

Urine volume would decrease and concentration would significantly rise

Question 8

When osmolality of blood rises, 3 homeostatic mechanisms are activated

Answer 8

1. Secretion of ADH (anti-diuretic hormone)
2. Thirst
3. Lesser players: ↓ renin → ↓ aldosterone → ↓ Na+ reabsorption; and ↓ ANF → ↓ renal flow

Question 9

Neurons from the supra optic nuclei (and paraventricular nuclei) emanate from the hypothalamus, project axons to the posterior pituitary to release

Answer 9

ADH or “vasopressin”

Question 10

What neuronal cell bodies are sensitive to osmolality of the blood?

Answer 10

Supra optic nuclei
Paraventricular nuclei

Note: these project axons to posterior pituitary to release ADH when osmolality rises

Question 11

When osmolality rises, what neurons secrete ADH and what does ADH do?

Answer 11

1. Supra optic nuclei and paraventricular nuclei
2. ADH enters blood stream, is delivered to renal collecting ducts to land on V2 receptors that cause the cells to add more aquaporins and therefore promote water reabsorption into the vasa recta

Question 12

↑ osmolality →

Answer 12

↑ ADH secretion → water retention (anti-diuresis)

The opposite is true as well:
↓ osmolality → ↓ ADH secretion → water loss (diuresis)

Question 13

Excessive sweating or osmotic diuresis (ie. Diabetes) may result in

Answer 13

Fluid shifting from intracellular compartment to the extra cellular compartment

Question 14

Excessive drinking (polydipsia) or excessive ADH may result in

Answer 14

Fluid shifting from the extracellular compartment to the intracellular compartment

Question 15

The effectiveness of ADH causes blood VOLUME to rise, this stimulates cessation of renin secretion. So:

↑ osmolality →

Answer 15

↑ osmolality → ↑ ADH secretion → water retention

→ ↓ renin secretion → ↓ aldosterone secretion → ↑ Na+ excretion → ↑ water excretion (with Na+)!

Question 16

When volume of blood falls, there powerful homeostatic mechanisms are activated:

Answer 16

1. Secretion of ADH
2. Secretion of renin, angiotensin and aldosterone
3. Lesser players: ↓ ANF → ↓ renal flow

Question 17

Fall in blood volume causes a fall in

Answer 17

BP

Question 18

Increased renin will cause 2 things:

Answer 18

↑ angiotensin I & II → some systemic constriction → ↑ BP

↑ aldosterone → ↑ Na+ reabsorption in distal nephron → ↓ fluid loss (into urine)

The opposite is also true:
↑ blood volume → ↓ renin/angiotensin & aldosterone → ↓ BP and ↑ water loss (from ↓ Na+ retention)

Question 19

Vomiting, diarrhea or excessive sweating (salt deficit) may result in

Answer 19

Fluid shifting from extracellular compartment to intracellular compartment

Question 20

And excessive intake of salt or adrenal hyperactivity (↑ aldosterone) may result in

Answer 20

Fluid shifting from intracellular compartment to the extracellular compartment