Fluid, Electrolyte, and Acid-Base Balance

Question 1

Fluid balance

Answer 1

When the amount of water you gain each day is equal to the amount you lose to the environment

Question 2

Electrolytes

Answer 2

Ions released when inorganic compounds dissociate

Question 3

Acid-base balance

Answer 3

When the production of hydrogen ions in your body is precisely offset by their loss

Question 4

ECF

Answer 4

Mostly interstitial fluid of peripheral tissues and the plasma of circulating blood

Question 5

ICF

Answer 5

Cytosol inside cells

Question 6

Fluid compartments

Answer 6

ECF and ICF

They commonly behave as seperate sections, maintaining different ionic compositions

Question 7

Principles of fluid and electrolyte balance

Answer 7

1. All the homeostatic mechanisms that monitor body fluids respond to changes in ECF not ICF
2. No receptors directly monitor fluid or electrolyte balance
3. Cells cannot move water molecules by active transport
4. The body’s content of water or electrolytes will increase if dietary gains exceed losses to the environment or vise versa

Question 8

ADH

Answer 8

Pituitary hormone that:

1. Promotes water retention by the kidneys
2. Stimulates hypothalmic thirst centre

Question 9

Aldosterone

Answer 9

Corticosteroid that stimulates sodium absorption by the kidneys

Question 10

Natriuretic peptides

Answer 10

Released by cardiac muscle cells in response to abnormal stretching of the heart walls because of high BP
Reduce thirst and block ADH so BP decreases

Question 11

Metabolic generation

Answer 11

Production of water within cells, primarily as a result of oxidative phosphorylation in mitochondria during aerobic metabolism

Question 12

Fluid shift

Answer 12

Water movement between ECF and ICF

Question 13

Importance of electrolyte balance

Answer 13

1. Total electrolyte concentrations directly affect water balance
2. Concentrations of individual electrolytes can affect cell functions

Question 14

What is the main cation in the ECF?

Answer 14

Sodium

Question 15

Equivalent (Eq)

Answer 15

Amount of a positive or negative ion that supplies 1 mole of electrical charge

Question 16

What is the main cation in the ICF?

Answer 16

Potassium

Question 17

Sodium balance

Answer 17

Depends on:

1. Sodium ion uptake across digestive epithelium
2. Sodium ion excretion by the kidneys and other sites

Question 18

Sodium ion regulatory mechanism

Answer 18

Changes ECF volume but keeps the Na+ concentration stable

Question 19

Hyponatremia

Answer 19

When the body’s water content increases enough to decrease the Na+ concentration of the ECF below 135mEq/L

Question 20

Hypernatremia

Answer 20

When the body’s water content decreases enough to increase the Na+ concentration of the ECF above 145mEq/L

Question 21

Potassium balance

Answer 21

Occurs by controlling the rate of active secretion by ion pumps along the DCT

Question 22

Factors affecting rate of tubular secretion of K+ into urine

Answer 22

1. Changes in the K+ concentration of the ECF
2. Changes in pH
3. Level of aldosterone

Question 23

Hypokalemia

Answer 23

Deficiency of K+ in the bloodstream

Muscle weakness and paralysis

Question 24

Hyperkalemia

Answer 24

Elevated level of K+ in the bloodstream

Cardiac arrhythmias

Question 25

Acidosis

Answer 25

When the pH of blood falls below 7.35

Question 26

Alkalosis

Answer 26

When the pH of blood rises above 7.45

Question 27

3 types of acids

Answer 27

1. Fixed acids: don’t leave solution
2. Metabolic acids: take part in cellular metabolism
3. Volatile acids: can leave the body and enter the atmosphere through the lungs

Question 28

Strong acids and bases

Answer 28

Dissociate completely in solution

Question 29

Weak acids and bases

Answer 29

When they enter a solution, a significant number of molecules remain intact

Question 30

Buffers

Answer 30

Dissolved compounds that stabilise the pH of a solution by adding or removing H+

Weak acids that can donate H+ and weak bases that can absorb H+

Question 31

Buffer system

Answer 31

Combination of a weak acid and the anion released by its dissociation

Question 32

Buffer systems of the body

Answer 32

1. Phosphate buffer system
2. Protein buffer systems
3. Carbonic acid-bicarbonate buffer system

Question 33

Phosphate buffer system

Answer 33

Has an important role in buffering the pH of the ICF and of urine

Question 34

Protein bugger systems

Answer 34

Contribute to the regulation of pH in the ECF and ICF

1. Hemoglobin buffer system (RBCs only)
2. Amino acid buffers (all proteins)
3. Plasma protein buffers

Question 35

Carbonic acid-bicarbonate buffer system

Answer 35

Prevent changes in pH caused by metabolic acids and fixed acids in the ECF

Question 36

Bicarbonate reserve

Answer 36

Readily available supply of HCO3-

Question 37

Respiratory compensation

Answer 37

A change in the respiratory rate that helps stabilise the pH of the ECF

Affects carbonic acid-bicarbonate buffer system

Rise in PCO2 > rise in respiratory rate

Question 38

Renal compensation

Answer 38

Change in the rates of H+ and HCO3- secretion or reabsorption by the kidneys in response to changes in plasma pH

Question 39

Respiratory acidosis

Answer 39

Develops when the respiratory system cannot eliminate all the CO2 generated by peripheral tissues

Question 40

Hypercapnia

Answer 40

Increased blood PCO2

Question 41

Respiratory alkalosis

Answer 41

Develops when respiratory activity lowers the blood PCO2 to a below normal level, hypocapnia

Question 42

Causes of metabolic acidosis

Answer 42

1. Production of a large number of fixed acids or metabolic acids
2. Lactic acidosis after exercise or hypoxia
3. Ketoacidosis from too much ketone bodies

Question 43

Metabolic alkalosis

Answer 43

Occurs when HCO3- concentration is elevated