Ch. 27: Fluid, electrolyte, and acid-base balance

Water is separated into 2 compartments: *

• intracellular fluid compartment

• extracellular fluid compartment

Osmolality

the concentration of solutes is a solution

Intracellular fluid compartment

all the fluid inside the cells of the body

___% of the water in our body is intracellular

70

Extracellular fluid compartment

extracellular fluid distributed throughout interstitial fluid, plasma, lymph, CFS, and synovial fluid

The same forces determining capillary perfusion determine exchange between ______ __________ *

fluid compartments

Osmolality differences drive water movement via _______ *

osmosis

Fluid balance depends on fluid ______ vs fluid ______

input/output

What are the 2 sources for fluid/water input

1. food/beverage (90% of fluid input)

2. cell metabolism (10%)

What are the 3 routes for fluid/water loss? *

1. urine (61% of fluid loss)

2. evaporation (35%)

   1. sweat and respiratory passages

3. feces (4%)

______ is a regulation of fluid intake.

Thirst

What are the 4 mechanisms that regulate thirst?

1. hypothalamic osmoreceptors

2. arterial and juxtaglomerulus apparatus

3. dryness of the mouth

4. distention of the stomach

Dehydration *

when blood volume drops below its normal range and osmolality is above normal range

Osmolality of solutes in the extracellular fluid _______, drawing water out of cells *

increases

Hyperhydration

extreme dilution of electrolytes in the blood from overconsumption of water

What happens to cells during hyperhydration?

cells well and their function is impaired

Sodium (Na +)

• function

• imblances

• function: dominant extracellular cation; exert extracellular osmotic pressure

  • 90-95% of extracellular osmotic pressure

• imbalances:

  • hyponatremia- low plasma levels of sodium

  • hypernatremia- high plasma levels of sodium

Chloride (Cl-)

• function

• imbalances

• function: predominant anions in extracellular fluid

• imbalances

  • hypochloremia- low plasma chloride concentration

  • hyperchloremia- high plasma chloride concentraiton

Potassium (K+) *

• function

• imbalances

• function: major intracellular cation; determines resting membrane potential

• imbalances:

  • hypokalemia- low potassium plasma concentration

  • hyperkalemia- high potassium plasma concentration

Calcium (Ca+):

• function

• imbalances

• function: involved in muscle contraction and exocytosis

• imbalances:

  • hypocalcemia- low calcium blood concentration

  • hypecalcemia- high calcium blood concentration

Phosphate (HPO4-):

• function

• imbalances

• function: form hydroxyapatite in bones; components of DNA/RNA/ATP;
  regulate enzyme activity; act as buffers

• imbalances

  • hypophosphatemia- low phosphate blood concentration

  • hyperphosphatemia- high phosphate blood concentration

Magnesium (Mg+):

• function

• imbalances

• function: co-factor for intracellular enzymes

  • helps Na/K pump function, among other enzymes

• imbalances:

  • hypomagnesemia- low magnesium blood concentration

  • hypermegnesemia- high magnesium blood concentration

What are the 3 hormonal mechanisms that regulate body fluid composition?

1. Renin-angiotensin-aldosterone hormone mechanism

2. atrial natriuretic hormone (ANH) mechanism

3. antidiuretic hormone (ADH) mechanism

Aldosterone _______ sodium and water reabsorption int he kidneys

increases

ANH ______ sodium and water reabsorption in the kidneys *

reduces

ADH _____ water reabsorption in the kidneys

increases

Acids *

proton-donating molecules

Bases *

proton-accepting molcecules

Acids and bases dissociate into their ________ ____ *

component ions

Buffers *

stabilize changes in pH by binding excess protons or releasing protons

What are the 2 mechanisms that regulate acid-base balance?

1. chemical buffer systems

2. physiological buffer systems

What are the 3 major chemical buffer systems?

1. carbonic acid/bicarbonate buffer system

2. protein buffer system

3. phosphate buffer system

Carbonic acid is formed when CO2 reacts with water

Proteins provide ~___% of the body’s buffer capacity

75

Proteins contain functional groups that act as _____/_____ *

acids/bases

________-containing molecules in solution act as biffers

• DNA, RNA, ATP

Phosphate

What are the 2 main physiological buffer systems? *

1. respiratory system

2. renal system

_______ system works in partnership with the carbonic acid/bicarbonate buffer system *

Respiratory

Alterations in ___ lead to alterations in ventilation

pH

The renal tubule cells directly regulate ____-____ balance

acid-base

Renal tubule cells control:

• the rate of proton secretion

• the rate of bicarbonate reabsorption

Homeostatic pH

7.35-7.45

Acidosis pH

pH below 7.35

Alkalosis pH

pH above 7.45

Respiratory acidosis/alkalosis

arising from respiratory abnormalities

Metabolic acidosis/alkalosis

arising from metabolic abnormalities