Chr. 27 - Fluid, Electrolyte, and Acid-Base Homeostasis

Question 1

[27.1] What is a body fluid?

Answer 1

A substance produced by the body consisting of water and dissolved solutes.

Two main types: intracellular fluid and extracellular fluid.

Question 2

[27.1] What is intracellular fluid?

Answer 2

Fluid with the cell.

Question 3

[27.1] What is extracellular fluid?

Answer 3

Fluid existing outside cells.

Question 4

[27.1] What is interstitial fluid?

Answer 4

Extracellular fluid existing in the microscopic spaces between tissue cells. 80% of extracellular fluid.

Question 5

[27.1] What is blood plasma?

Answer 5

Extracellular fluid composing the liquid portion of blood. 20% of extracellular fluid.

Question 6

[27.1] What is fluid balance?

Answer 6

The required amount of water and solutes correctly proportioned among the various compartments.

Question 7

[27.1] What is the largest signle component of the body?

Answer 7

Water, 45-75% of total mass.

Question 8

[27.1] What is an electrolyte?

Answer 8

Inorganic compounds that dissociate into ions when dissolved. Affects fluid balance through osmosis.

Question 9

[27.1] What is metabolic water?

Answer 9

Water produced in the body when electrons are accepted by oxygen during aerobic respiration. 200mL/day

Question 10

[27.1] What is the thirst center?

Answer 10

An area of the hypothalamus governing the urge to drink.

Question 11

[27.1] What is dehydration?

Answer 11

A decrease in water volume and increase in osmolarity of body fluids.

Question 12

[27.1] What are osmoreceptors?

Answer 12

Receptors in the hypothalamus that detect increased blood osmolarity and stimulate the thirst center.

Question 13

[27.1] What receptors stimulate the thirst center?

Answer 13

Water BANS:
1. Baroreceptors in blood vessels
2. Angiotensin II
3. Neurons within the mouth detecting dryness.
4. Stretch receptors in the atria

Question 14

[27.1] How does elimination of excess body water occur?

Answer 14

Mainly by control of urine output.

Question 15

[27.1] What is the main factor of urine output determining body fluid volume?

Answer 15

Urinary salt loss.

Question 16

[27.1] What is the main hormone regulating water loss?

Answer 16

Antidiuretic hormone.

Question 17

[27.1] Which other hormones play a role in fluid balance?

Answer 17

Aldosterone and atrial natriuretic peptide.

Question 18

[27.1] How does aldosterone play a role in fluid balance?

Answer 18

Promotes reabsorption of sodium in the distal convoluted tubule and collecting ducts. Water follows the sodium, increasing blood volume.

Question 19

[27.1] How does atrial natriuretic peptide play a role in fluid balance?

Answer 19

Promotes natriuresis, elevated excretion of sodium into urine leading to increase water loss.

Question 20

[27.1] What is hypertonicity of extracellular fluid?

Answer 20

When solutes occur in greater concentration within extracellular fluid, drawing out fluid from within cells and causing them to shrink.

Question 21

[27.1] What is hypotonicity of extracellular fluid?

Answer 21

When solutes within a cell occur at greater concentration than extracellular fluid, leading to movement of water into cells and causing swelling.

Question 22

[27.1] What is water intoxication?

Answer 22

A state in which excessive body water causes cells to swell dangerously, occurs when water intake occurs faster than kidneys can excrete it.

Question 23

[27.2] List the four general functions of ions within the body.

Answer 23

1. Control osmosis of water between compartments
2. Maintain acid-base balance
3. Carry electrical current
4. Serve as cofactors for enzymes.

Question 24

[27.2] What is milliequivalents per liter (mEq/liter)?

Answer 24

The unit of measurement expressing the concentration of ions. Typically 1mmol/liter for ions with a single charge, and 2mmol/liter for ions with two charges, positive or negative.

Question 25

[27.2] What is an equivalent?

Answer 25

A positive or negative charge equal to the charge of one mole of hydrogen; 1g of hydrogen.

Question 26

[27.2] What is a milliequivalent?

Answer 26

One one-thousandth of an equivalent.

Question 27

[27.2] What is the most abundant ion in extracellular fluid?

Answer 27

Sodium, most abundant ion, and most abundant positive ion.

136 - 148 mEq/liter in blood plasma.

Question 28

[27.2] What is hyponatremia?

Answer 28

Blood plasma concentration of sodium below 135 mEq

Question 29

[27.2] What is hypernatremia?

Answer 29

Blood plasma concentration of sodium above 148 mEq

Question 30

[27.2] What is the most abundant negative ion in extracellular fluid?

Answer 30

Chloride.

95 - 105 mEq in blood plasma.

Question 31

[27.2] What is the most abundant cation in intracellular fluid?

Answer 31

Potassium

3.5 - 5 mEq in blood plasma.

Question 32

[27.2] Why does the mEq/liter of bicarbonate fluxuate?

Answer 32

As blood absorbs carbon dioxide from cellular metabolic waste, it combines with water in the blood plasma to form bicarbonate.

22 - 26 mEq in arterial blood plasma
23 - 27 mEq in venous blood plasma

Question 33

[27.2] What is the most abundant mineral in the body?

Answer 33

Calcium.

4.5 - 5.5 mEq in blood plasma.

Question 34

[27.2] Describe the presence of phosphate in the body.

Answer 34

Occurs as calcium phosphate salts in bones and teeth, as phosphate ions ((H2PO4)-, (HPO4)2-, and (PO4)3-) acting as intracellular anions and a buffer for hydrogen ions.

1.7 - 2.6 mEq in blood plasma.

Question 35

[27.2] What hormones regulate calcium and phosphate levels?

Answer 35

Parathyroid hormone and calcitriol.

Question 36

[27.2] Describe the presence of magnesium in the body.

Answer 36

Occurs as magnesium salts forming bone, as well as intracellular cations. Also acts as a cofactor for enzymes.

1.3 - 2.1 mEq in blood plasma.

Question 37

[27.3] List the major mechanisms for removal of hydrogen ions from body fluids.

Answer 37

1. Buffer systems
2. Exhalation of carbon dioxide
3. Kidney excretion of hydrogen

Question 38

[27.3] What is a buffer system?

Answer 38

A mechanism composed of a weak acid and a weak base, typically a salt formed from the acid. Prevents rapid, drastic changes of pH by converting strong acids and bases to weaker ones.

Question 39

[27.3] Describe the protein buffer system.

Answer 39

A prolific buffer system between intracellular fluid and blood plasma utilizing the carboxyl and amino groups of amino acids, as well as side chains of 7/20 amino acids. Able to buffer acids and bases.

Question 40

[27.3] Describe the carbonic acid - bicarbonate buffer system.

Answer 40

A buffer system utilizing bicarbonate as a weak base and carbonic acid as a weak acid. Carbonic acid provides flexibility, removing excess hydrogen and dissociating into water and carbon dioxide, or release hydrogen ions and forming bicarbonate.

Question 41

[27.3]