Chapter 24: Water & Electrolyte

Question 1

Newborn baby’s body weight is about

Answer 1

75% water

Question 2

Total body water (TBW)

Answer 2

content of average young adults is 60% in men and 50% in women

Question 3

obese and elderly people body water %

Answer 3

as little as 45% by weight

Question 4

why is women’s totals body water average slightly less?

Answer 4

they have more adipose tissue, which displaces water

Question 5

Fluid compartments

Answer 5

areas separated by selectively permeable membranes and differing in chemical composition

Question 6

ECF is divided into

Answer 6

• 25% tissue (interstitial) fluid
• 8% blood plasma and lymph
• 2% transcellular fluid

Question 7

intracellular fluid (ICF) %

Answer 7

65%

Question 8

extracellular fluid (ECF)

Answer 8

35%

Question 9

Fluid balance

Answer 9

when daily water gains and losses are equal (about 2,500 mL/day)

Question 10

gains come from which two sources?

Answer 10

metabolic water and performed water

Question 11

Metabolic water

Answer 11

formed by aerobic metabolism and dehydration synthesis

Question 12

Preformed water

Answer 12

ingested in food and drink

Question 13

cutaneous transpiration

Answer 13

water that diffuses through epidermis and evaporates

Question 14

Insensible water loss

Answer 14

not usually aware of it; breath and cutaneous transpiration

Question 15

Sensible water loss

Answer 15

noticeable output; urine and moderate sweating

Question 16

Fluid deficiency

Answer 16

fluid imbalance that arises when fluid output exceeds intake over long period of time

Question 17

Volume depletion (hypovolemia)

Answer 17

• proportional amounts of sodium and water are lost without replacement
• Total body water declines but osmolarity remains normal
• Caused by hemorrhage, burns, chronic vomiting or diarrhea, aldosterone hyposecretion (Addison disease)

Question 18

Dehydration (negative water balance)

Answer 18

• body eliminates significantly more water than sodium
• ECF osmolarity rises
• Caused by lack of water intake, diabetes mellitus, diabetes insipidus (ADH hyposecretion), profuse sweating, overuse of diuretics

Question 19

why is fluid excess is much less common than fluid deficiency?

Answer 19

because kidneys are highly effective in compensating for excessive intake by excreting more urine

Question 20

Volume excess

Answer 20

• both sodium and water are retained and ECF remains isotonic
• Caused by aldosterone hypersecretion or renal failure

Question 21

Hypotonic hydration (water intoxication or positive fluid balance)

Answer 21

• more water than sodium is retained or ingested and ECF becomes hypotonic
• lose large amounts of water and salt through urine and sweat, but replace it by drinking only plain water

Question 22

Fluid sequestration

Answer 22

• excess accumulation of fluid in a particular location
• Hemorrhage can cause fluid sequestration as blood pools and clots in the tissues

Question 23

Edema

Answer 23

accumulation of fluid in interstitial spaces; most common form of fluid sequestration

Question 24

Pleural effusion

Answer 24

fluid accumulation in pleural cavity, caused by some lung infections

Question 25

Functions of sodium

Answer 25

• gradient is a source of potential energy for cotransport of other solutes such as glucose, potassium, and calcium
• sodium potassium pump
• important means of generating body heat

Question 26

Sodium imbalances

Answer 26

Hypernatremia and Hyponatremia

Question 27

Hypernatremia

Answer 27

• plasma sodium concentration greater than 145 mEq/L
• From administration of IV saline
• Complications : Water retention, hypertension

Question 28

Hyponatremia

Answer 28

• plasma sodium concentration less than 130 mEq/L
• Person loses large volumes of sweat or urine, replacing it with drinking plain water
• Result of excess body water, quickly corrected by excretion of excess water

Question 29

Functions of potassium

Answer 29

• Electrical signaling in nerve and muscle cells
• most abundant cation of ICF
• Greatest determinant of intracellular osmolarity and cell volume
• Essential cofactor for protein synthesis and other processes
• sodium potassium pump

Question 30

Potassium imbalance

Answer 30

• Most dangerous types of electrolyte imbalances
• Hyperkalemia and hypokalemia

Question 31

Hyperkalemia

Answer 31

plasma potassium concentration above 5.5 mEq/L&raquo_space; Increased Excitability

Question 32

Hypokalemia

Answer 32

plasma potassium concentration less than 3.5 mEq/L&raquo_space; Nerve and muscle cells Decreased excitablilty

Question 33

chemical buffer

Answer 33

• substance that binds + H and removes it from solution as its concentration begins to rise, or releases +H into solution as its concentration fall
• restores normal pH in fraction of a second

Question 34

buffer systems

Answer 34

mixtures composed of weak acids and weak bases

Question 35

Three major chemical buffers

Answer 35

bicarbonate, phosphate, and protein systems

Question 36

Bicarbonate buffer system

Answer 36

solution of carbonic acid and
bicarbonate ions (Carbonic anhydrase enzyme)

Question 37

Protein buffer system

Answer 37

• proteins act as buffers due to the side groups of their amino acids
• accounts for about three-quarters of all chemical buffering in the body fluids
• Proteins are more concentrated than bicarbonate or phosphate systems, especially in the Intracellular ICF

Question 38

acidosis

Answer 38

HYPERVENTILATION

Question 39

alkalosis

Answer 39

HYPOVENTILATION

Question 40

what can neutralize more acid or base than either the respiratory system or chemical buffers?

Answer 40

the kidneys