chap 26 Fluid, Electrolyte & Acid-Base Balance a&p 2

Water

The most abundant component of body fluids

Solvent

A substance that does the dissolving

Preformed water

Water obtained from ingested food and drinks; about 90% of body water

Metabolic water

Water produced during cellular respiration; about 10% of body water

Total body water

About 40 liters in an average adult

Human body water percentage

Humans are approximately 50-60% water

Infant water content

More than 73% of body weight

Adult male water content

About 60% of body weight

Adult female water content

About 50% of body weight due to higher body fat and lower muscle mass

Elderly water content

About 45% of body weight

Intracellular fluid (ICF)

Fluid located inside cells; about 70% of body water

Cytosol

Another name for the fluid inside cells

Extracellular fluid (ECF)

Fluid outside cells; about 30% of body water

Interstitial fluid (IF)

Fluid located between cells; about two-thirds of extracellular fluid

Blood plasma

The fluid portion of blood; about one-third of extracellular fluid

Solute

A substance dissolved in a solvent

Solution

A mixture of solute(s) and solvent

Electrolytes

Solutes that dissociate into ions when added to water

Nonelectrolytes

Substances that do not dissociate into charged particles in water

Cations

Positively charged ions

Anions

Negatively charged ions

Osmotic power

The ability of a substance to cause fluid shifts

Electrolyte electrical property

Electrolytes can conduct electrical current

Electrolyte examples

Sodium potassium chloride bicarbonate calcium magnesium and some proteins

Nonelectrolyte examples

Glucose lipids creatinine and urea

ICF most abundant cation

Potassium (K+)

ICF most abundant anions

Phosphates and proteins

ECF most abundant cation

Sodium (Na+)

ECF most abundant anion

Chloride (Cl-)

Plasma versus interstitial fluid

Plasma contains more proteins than interstitial fluid

pH

A measure affecting functional proteins and biochemical reactions in the body

Normal blood pH

7.35-7.45

Alkalosis

Arterial blood pH greater than 7.45

Acidosis

Arterial blood pH less than 7.35

Buffers

Substances or systems that prevent drastic changes in pH

Acid-base balance

Regulation of body fluid pH within a narrow range

Respiratory acidosis

An acid-base imbalance caused by respiratory system failure to balance pH

Respiratory alkalosis

An acid-base imbalance caused by respiratory system failure to balance pH

Metabolic acidosis

A pH abnormality caused by something other than pCO2

Metabolic alkalosis

A pH abnormality caused by something other than pCO2

Respiratory acid-base indicator

Blood pCO2

Metabolic acid-base indicator

Blood bicarbonate (HCO3-) levels

Causes of respiratory acidosis

Hypoventilation impaired lung function and impaired ventilatory movement

Hypoventilation

Reduced ventilation that can contribute to respiratory acidosis

Causes of respiratory alkalosis

Hyperventilation strong emotions and hypoxemia

Hyperventilation

Increased ventilation that can contribute to respiratory alkalosis

Hypoxemia

A low concentration of oxygen in the blood

Causes of metabolic acidosis

Severe diarrhea renal disease untreated diabetes starvation and excess alcohol ingestion

Causes of metabolic alkalosis

Vomiting gastric suctioning excessive sodium bicarbonate ingestion and excess aldosterone

Chemical buffer systems

The immediate acid-base regulation mechanism; acts within seconds

Respiratory regulation

An acid-base regulation mechanism that acts within 1-3 minutes

Renal mechanisms

The slowest but most powerful acid-base regulation mechanism; acts over hours to days

Physiological buffering systems

The respiratory system and urinary system

Buffer system compensation

If one physiological buffering system malfunctions the other attempts to compensate

Effect of increased CO2 on pH

Increased CO2 decreases pH and makes body fluids more acidic

Effect of decreased CO2 on pH

Decreased CO2 increases pH and makes body fluids more basic

Bicarbonate buffer system

A system in which bicarbonate can bind free H+ to help neutralize acids

Bicarbonate (HCO3-)

An ion that can bind hydrogen ions (H+) to form carbonic acid

Carbonic acid (H2CO3)

A compound formed from CO2 and H2O in the bicarbonate buffer system

High pCO2 or H+ concentration

Makes plasma more acidic

Low pCO2 or H+ concentration

Makes plasma more basic

Hyperventilation and CO2

Hyperventilation removes excess CO2 and pushes the buffer reaction to the left

Hypoventilation and CO2

Hypoventilation retains CO2 and pushes the buffer reaction to the right

Renal buffering

Kidney regulation that makes large pH changes but takes hours to days

Fixed acids

Metabolic wastes such as phosphoric acid lactic acid uric acids and ketones

Renal acid-base functions

Eliminate fixed acids and conserve or generate bicarbonate

Renal H+ regulation

Involves secretion of H+ and reabsorption or generation of HCO3-

Blood pH too high

Kidneys excrete excess bicarbonate and retain H+ to decrease pH

Blood pH too low

Kidneys reabsorb or generate bicarbonate and secrete H+ into urine to increase pH

Kidneys and bicarbonate

Kidneys can excrete excess bicarbonate or reabsorb and generate more bicarbonate

Kidney tubule cell permeability

Tubule cells are impermeable to bicarbonate but permeable to CO2

Bicarbonate movement into kidney tubules

Bicarbonate can be converted into CO2 to move from blood into tubules

CO2 inside kidney tubule cells

CO2 can be converted back into bicarbonate or travel to the lungs for expiration