Body Fluid Homeostasis

Question 1

What is the physiological blood glucose range for homeostasis?

Answer 1

70-99 mg/dL

Question 2

What is the physiological range for pH in homeostasis?

Answer 2

7.35 -7.45

Question 3

What is the physiological range for sodium concentrations to maintain homeostasis?

Answer 3

135 - 145 mEq/L

Question 4

What is the physiologic range for Potassium to maintain homeostasis?

Answer 4

3.5 - 5.5 mM/L

Question 5

How does the brain regulate fluid concentrations in the blood?

Answer 5

• Magnocellular neurons of the hypothalamus receive information about ECF osmolality and blood pressure and will produce & release vasopressin (ADH) into the blood vessels of the posterior pituitary to help maintain osmolality within a narrow physiological range

Question 6

What is the osmolality of a
100 mM glucose solution?

A.100 mOsmol/Kg
B.200 mOsmol/Kg
C.300 mOsmol/Kg
D.400 mOsmol/Kg

Answer 6

A.100 mOsmol/Kg

Question 7

What is the osmolarity of a 100 mM sodium chloride solution?

A.100 mOsmol/L 
B.188 mOsmol/L 
C.200 mOsmol/L 
D.300 mOsmol/L 
E.400 mOsmol/L

Answer 7

C.200 mOsmol/L

Question 8

What are the main actions of Vasopressin?

Answer 8

• Increased Water reabsorption
• decrease in EC fluid osmolality
• More concentrated Urine

Question 9

What are the main actions of the RAAS?

Answer 9

• Vasoconstriction
• Increased Na+ reabsorption
• Water retention

Question 10

Which cells of the kidney are stimulated by the SNS (EP/NP) to release renin?

Answer 10

Juxtaglomerular cells

Question 11

What affect does the SNS have on the proximal convoluted tubule?

Answer 11

Increases Na+ reabsorption

Question 12

What is the approximate total body water volume of a 70 kg, 25 year-old normal healthy male?

A. 22 L 
B. 32 L 
C. 42 L 
D. 52 L 
E. 62 L

Answer 12

C. 42 L

Question 13

What is the approximate intracellular fluid volume of a 70 kg, 25 year-old normal healthy male?

A. 18 L 
B. 28 L 
C. 42 L 
D. 38 L 
E. 8 L

Answer 13

B. 28 L

Question 14

What is the body fluid percentage of intracellular fluid volume?

Answer 14

40%

Question 15

What percentage of body weight is water?

Answer 15

60%

Question 16

What are the percentages of fluid weight are IF, Plasma, and adipose?

Answer 16

IF -> 16 % (10 L)

Plasma -> 4% (2.5 L)

Adipose -> 3-30%

Question 17

What is the osmolality of blood?

Answer 17

300 mOsmol/Kg

Question 18

What are the 3 main ions in plasma and interstitial fluid?

Answer 18

Na+, Cl-, and HCO3-

Question 19

What are the 3 most abundant ions in intracellular fluid?

Answer 19

K+, Phosphates, and Proteins

Question 20

How is osmolality estimated?

Answer 20

2* [Na+] + [glucose] + [Urea] (molecules/L)

*Clinical labs often give glucose and Urea in mg/dL which you must convert to molecules/ L

Question 21

Which 2 of the following are true statements? [select all that apply]
A. Total body water as a % of body weight
increases with age.
B. The extracellular fluid volume is greater
than the intracellular fluid volume.
C. The extracellular fluid osmolality is
equal to the intracellular fluid osmolality.
D. Plasma osmolality is equal to the plasma
tonicity.
E. [Na+] is greater in extracellular fluid than
intracellular fluid.

Answer 21

C. The extracellular fluid osmolality is
equal to the intracellular fluid osmolality.

E. [Na+] is greater in extracellular fluid than
intracellular fluid.

Question 22

Why is Urea not included int he toxicity calculation?

Answer 22

• Urea is freely permeable
• A solute does not create a lasting osmotic
  effect if it is freely permeable to the
  membrane and will equilibrate across the
  membrane

Question 23

How is plasma tonicity calculated?

Answer 23

Tonicity = 2 * [Na+] + [glucose] (molecules/L)

Question 24

Which type of solution will cause cells to crenate?

Answer 24

Hypertonic

Question 25

What is the osmality of a Na+ isotonic solution?

Answer 25

154 mmol/Kg

Question 26

What is the osmolality of an isotonic NaCl solution?

Answer 26

154 + 154 = 308 mOsm/ Kg

Question 27

Which of the following would you expect from the IV infusion of 1 L isotonic saline into a patient? [disregard urine output] [select all that apply] A. Total body water increases ~ 1 L. B. Extracellular fluid (ECF) volume increases ~ 500 mL and the intracellular fluid (ICF) volume increases ~ 500 mL. C. ECF volume increases ~ 333 mL and the ICF volume increases ~ 666 mL. D. ECF volume increases ~ 666 mL and the ICF volume increases ~ 333 mL. E. ECF volume increases ~ 1 L.

Answer 27

A. Total body water increases ~ 1 L. E. ECF volume increases ~ 1 L.

Question 28

What is RVD and what are it’s long term effect?

Answer 28

- Activated by cell swelling caused by hypotonic ECF - Typically caused by hyponatremia - Causes activation of regulatory mechanisms to compensate resulting in net movement of K+ and Cl- out of cell. - End result can be osmotic demyelination syndrome or other harmful CNS effects

Question 29

What is RVI, it’s causes, and it’s long term effects?

Answer 29

- Activaetd by cell shrinkage due to hypertonic ECF - Caused by hypernatremia, hyperglycemia, etc. - Acute response: Increase Intracellular K+/Cl-, Na/H exchanger causes alkalinizing of cytoplasm, activation if Cl-/HCO3- transporter - Chronic: generation of Diogenes osmoles; cells produce taurine, glycine, glutamine, sorbitol. And inositol

Question 30

What is the importance of correction speed for osmotic imbalances?

Answer 30

Correction of disorders of Na+ and water balance should be done slowly to avoid serious neurological complications Can cause cerebral edema, seizures, neurological damage, CPM, and the zombie apacolypse

Question 31

What is Bulk Flow?

Answer 31

hydrostatic pressure differences | moving molecules in the same direction much faster than can be accounted for by diffusion

Question 32

What is ultrafiltration?

Answer 32

separation by size of solutes in a | solution achieved by forcing the solution through a filter

Question 33

What is Oncotic pressure?

Answer 33

Oncotic pressure is the osmotic pressure generated by large molecules in solution, and is an important force keeping fluid inside blood vessels

Question 34

How is CFR calculated?

Answer 34

CFR = Kf [(Pc-Pisf) - σ(πc - πisf)] Kf= Ultrafiltration coefficient (product of permeability and surface area) PC = Hydrostatic pressure in capillary Pisf= Hydrostatic pressure in interstitial fluid σ= Reflection coefficient for protein πC= Oncotic pressure in capillary (primarily plasma proteins) πisf = Oncotic pressure in interstitial fluid

Question 35

What are the forces moving fluid at the arterial end of a capillary? * Some of these aren’t in the lecture, but were gathered from outside sources to be more accurate

Answer 35

Capillary Pressure: 30 mmHg Negative interstitial free fluid pressure: 3 mmHg Interstitial fluid colloid osmotic pressure: 8 mmHg Plasma Colloid osmotic pressure: - 28 mmHg NET: 13 mmHg

Question 36

Which of the following would you expect from the IV infusion of 1 L 0.45% NaCl (145 mOsm/kg H2O) into a patient? [disregard urine output] ``` A. ECF volume increases ~ 500 mL and ICF volume increases ~ 500 mL. B. ECF volume increases ~ 333 mL and ICF volume increases ~ 666 mL. C. ECF volume increases ~ 666 mL and ICF volume increases ~ 333 mL. D. ECF volume increases ~ 1000 mL and ICF 0% volume increases ~ 0 mL. E. ECF osmolality increased ```

Answer 36

C. ECF volume increases ~ 666 mL and ICF | volume increases ~ 333 mL.

Question 37

Which of the following would you expect from the IV infusion of 1 L 5% dextrose in water into a patient? [disregard urine output] ``` A. ECF volume increases ~ 500 mL and ICF volume increases ~ 500 mL. B. ECF volume increases ~ 333 mL and ICF volume increases ~ 666 mL. C. ECF volume increases ~ 1000 mL and ICF volume increases ~ 0 mL. D. ECF volume increases ~ 666 mL and ICF volume increases ~ 333 mL. E. ECF osmolality has increased ```

Answer 37

B. ECF volume increases ~ 333 mL and ICF | volume increases ~ 666 mL.

Question 38

What is specific gravity? When can it be high?

Answer 38

- Specific gravity is defined as the weight of a volume of solution divided by the weight of an equal volume of distilled water - Urine specific gravity can be high (1.040 to 1.050) in patients who have received an injection of radiocontrast dye even though the urine osmolality is similar to that of plasma * Normal human plasma has a specific gravity in the range of 1.008 to 1.010