Chapter 20: Fluid, Electrolyte, and Acid-Base Homeostasis

BIOS 213

a lean adult human has between ___ of body mass in fluids

55-60%

Body fluids are made up of two compartments:

intracellular fluid and extracellular fluid

intracellular fluid -

within cells

extracellular fluid -

that which surrounds the cells, including plasma and interstitial fluid

contributing factors of water gain:

ingestion and metabolic synthesis

contributing factor(s) of water loss:

all the above

average % of solids in a male:

45%

average % of solids in a female:

40%

average % of liquids in a male:

55%

average % of liquids in a female:

60%

of the 55-60% of fluids in the body, ___ are made up of intracellular fluid

2/3

of the 55-60% of fluids in the body, ___ are made up of extracellular fluid

1/3

extracellular fluid is made up of ___ interstitial fluid

80%

extracellular fluid is made up of ___ plasma

20%

the thirst response is regulated by the thirst center in the:

hypothalamus

dehydration causes:

decreased BV → deceased BP

the thirst center is stimulated by:

all the above

the thirst center is stimulated by:

all the above

ADH release is stimulated by:

both

ADH inserts:

aquaporin II proteins into principal cells

ADH increases:

water reabsorption

ADH is inhibited by:

alcohol

hormone(s) that regulate(s) water and solute loss:

all the above

aldosteron releases is triggered by:

decreased BP or Na⁺

decreased BP or Na⁺ activates:

renin-angiotensin-aldosterone pathway

aldosterone increases:

Na⁺ reabsorption, which promotes water reabsorption

atrial natriuretic peptide release is stimulated by:

volume receptors that detect increased stretch of atria

atrial natriuretic peptide increases:

excretion of Na⁺ in urine (prevents Na⁺ reabsorption) leads to loss of more water in urine

electrolytes -

ions dissolved in body fluids

certain ions control:

osmosis of water between fluid compartments

ions maintain:

acid-base balance

ions carry:

electrical current

ions serve as:

enzyme cofactors

electrolyes include:

sodium, chloride, potassium, bicarbonate, calcium, phosphate, magnesium

most abundant cation in extracellular fluid:

sodium

sodium accounts for ___ of extracellular osmolarity

1/2

plays a role in action potential generation/conduction:

sodium

sodium concentrations are controlled by:

all the above

most abundant anion in extracellular fluid:

chloride

chloride moves easily across most membrane channels via:

Cl^- leak channels

helps balance anion levels in fluid compartments:

chloride

most abundant cation in intracellular fluid:

potassium

plays a key role in establishing the resting membrane potential and repolarization phase of action potential:

potassium

helps regulate blood pH:

bicarbonate

mechanism of CO₂ homeostasis:

bicarbonate

large amount stored in bone:

calcium

hormonally regulated:

calcium

major signaling molecule (neurotransmitter release):

calcium

important buffer:

phosphate

function as cofactor for many enzymes:

magnesium

pH levels affect:

both

pH must be kept at normal levels, which is around:

7.4

major mechanism for controlling blood pH:

all the above

buffer system:

quickly but temporarily bind to H⁺ and increase pH

exhalation of CO₂:

increase rate and depth of breathing releases excess CO₂ → reduces carbonic acid levels → increases pH

slowest acid-base controlling mechanism:

kidney excretion of H⁺

Kidney secretion of H⁺ ___ pH

increases

only way to eliminate acids:

kidney excretion of H⁺

if there is too little H⁺:

H₂CO₃^- can provide H⁺ → increasing pH

if there is too much H⁺:

H₂CO₃^- can remove H⁺ → decreasing pH

most abundant in ICF and plasma:

both

if pH is increased to above 7.45, the protein buffer system:

adds H⁺ to the carboxyl group and amino acid → lowering pH

if pH is decreased to below 7.35, the protein buffer system:

removes H⁺ from the carboxyl group and amino acid → raising pH

an important buffer in RBCs:

hemoglobin

Important buffer in intracellular fluid:

phosphate

H₂PO₄^- can serve as a ____ that buffers ___

weak acid; OH-

HPO₄^2- can serve as a ____ that removes ____

weak base; H+

exhalation of carbon dioxide helps:

eliminate H⁺ ions

If pH decreases:

respiratory rate increases

if P_CO2 increase:

respiratory rate increases

if pH increases:

respiratory rate decreases

if P_CO2 decreases:

respiratory rate decreases

in renal regulation of pH in the proximal tubule:

both

the most important cells in renal regulation of pH:

intercalated cells

the first type of intercalated cell contains:

both

the second type of intercalated cell contains:

both

acidosis -

when blood pH drops below the normal range because of excess H+ load

when blood pH is below 7.35:

acidosis

alkalosis -

when the blood pH rises above the normal range because of deficit in H⁺ load

when blood pH is above 7.45:

alkalosis

respiratory acidosis -

increased P_CO2 (above 45 mmHg) and decreased pH if there is no compensation

common causes of respiatory acidosis:

hypoventilation due to emphysema, pulmonary edema, trauma to respiratory center, airway obstructions, dysfunction of muscles and respiration

compensatory mechanism of respiratory acidosis:

renal: increased secretion of H+; increased reabsorption of HCO3-

respiratory alkalosis -

decreased P_CO2 (below 35 mmHg) and increased pH if there is no compensation

common causes of respiratory alkalosis:

hyperventilation due to oxygen deficiency, pulmonary disease, cerebrovascular accident, severe anxiety

compensatory mechanism of respiratory alkalosis:

renal: decreased excretion of H+; decreased reabsorption of HCO3-

metabolic acidosis -

decreased HCO3- (below 22mEq/liter) and decreased pH if there is no compensation

common causes of metabolic acidosis:

loss of bicarbonate ions due to diarrhea, accumulation of acid, renal dysfunction

compensatory mechanism of metabolic acidosis:

respiratory: hyperventilation, which increases loss of CO2

metabolic alkalosis -

increased HCO3- (above 26mEq/liter) and increased pH if there is no compensation

common causes of metabolic alkalosis:

loss of acid due to vomiting, gastric suctioning, or use of certain diuretics, excessive intake of alkaline drugs

compensatory mechanism of metabolic alkalosis:

respiratory: hypoventilation, which slows loss of CO2