Water, Electrolyte, & Acid-Base Balance

Water balance

When the amount of water gained each day is equal to the amount lost to the environment.

Intake = output

Electrolyte

Charged atoms (ions) dissolved in water

(EX: Sodium (Na+), Chlorine (Cl-), Potassium (K+)

Electrolyte balance

Electrolyte balance occurs when electrolyte absorption in the digestive tract equals electrolytes excretion by the kidneys.

Acid-base balance

Maintenance of the production and loss of hydrogen ions in body fluids

Extracellular fluid (ECF)

All fluids outside of cells

Intracellular fluid (ICF)

All of the fluids inside of the cells

What is the dominant ion in the extracellular fluid?

Sodium

What dominant ion in intracellular fluid?

Potassium

What are the the 2 subdivisions in the ECF?

• Interstitial fluid

• Plasma

Where does exchange between the two ECF division occur?

Primarily across the endothelial lining of capillaries

What is the normal range of pH in the human body?

7.35 - 7.45

Acidosis

Occurs when pH falls below 7.35

Alkalosis

Occurs when pH above 7.45

What acid is formed when carbon dioxide combines with water?

Carbonic acid

What two electrolytes does carbonic acid break down into?

Bicarbonate ion

Hydrogen ion

What happens to pH levels when blood carbon dioxide levels increase?

pH will decrease (become more acidic) because carbonic acid levels increases and therefore hydrogen ion increase

What happens to pH levels when carbon dioxide levels decreases?

pH levels increase (becomes more alkaline) because carbonic acid decreases, therefore hydrogen ions decrease

Buffer

Dissolved compounds that can provide or remove hydrogen ions to stabilize the pH of a solution

Buffer systems

A chemical system that maintains the pH of a solution by neutralizing excess acids or bases, crucial for regulating pH in biological systems

They can soak up excess acids or bases (keeps pH STABLE!!)

Acid

A compound that releases hydrogen ions (H+) when dissolved in water

Acids increase the concentration of H+ions in a solution

Base

Bases can reduce the concentration of H+ ions in a solution by binding to them

Protein Buffer System

Regulates pH of ICF and ECF by accepting or donatinf hydrogens ions on amino acid groups (-COOH, -NH₂ )

Carbonic acid-bicarbonate buffer system

Works in ECF; carbonic acid (H₂CO₃) is a weak acid that can donate hydrogen ions (H+), and bicarbonate ions (HCO^-₃) are weak base that can accept hydrogen ions

H₂CO₃ → ← H⁺ + HCO^-₃

Phosphate Buffer System

Consists of H₂PO₄^- (weak acids) and HPO₄^- (weak base), works in both ECF or ICF

Respiratory compensation

Changes in respiratory rate that change carbon dioxide levels.

CO₂ is sensed by chemoreceptors in carotid and aortic bodies to signal CNS to adjust respiratory rate

Renal Compensation

Changes in rates of hydrogen ion and bicarbonate ion secretion and absorption by the kidneys

Respiratory acidosis

A condition where the lungs cannot remove enough carbon dioxide from the body, leading to decreased pH (increased acidity) in blood and tissue.

Most commonly caused by hypoventilation

Respiratory alkalosis

Increased respirations (hyperventilation) cause a drop in carbon dioxide concentration, causing pH to become too alkaline

Not common because body quickly compensates

Metabolic acidosis

Caused by large production of metabolic acids like lactic acid or ketone bodies, or kidneys not excreting adequate amounts of hydrogen ions

Metabolic alkalosis

Occurs when bicarbonate ion concentration becomes elevated or following excessive loss hydrogen ions

(EX: vomiting)