Chapter 26 Recorded Lecture

The pH scale measures hydrogen-ion concentration, defining acids (pH below 7) and bases (pH above 7). Blood pH imbalances are termed acidosis (below 7.35) or alkalosis (above 7.45). Strong acids fully dissociate, while weak acids partially ionize.

Three classes of acids threaten pH balance: fixed acids (eliminated by kidneys), organic acids (byproducts of metabolism), and volatile acids (exhaled by lungs, e.g., carbonic acid). The respiratory system regulates blood pH by adjusting CO2 levels, and kidneys conserve bicarbonate.

Water balance is regulated by hormones, primarily Antidiuretic Hormone (ADH), and depends on sodium balance. Obligatory water output (urine, skin, lungs, feces) must be balanced with water intake (foods, liquids, metabolic water). The thirst response and the role of ANP and aquaporins are also discussed.

Disturbances in water balance can lead to dehydration (water loss exceeding gain) or hypotonic hydration (water gain exceeding loss). Dehydration causes cell crenation, while hypotonic hydration can lead to cell lysis.

Electrolyte balance involves the regulation of sodium, potassium, chloride, calcium, and phosphate. Sodium is regulated by aldosterone and ANP. Potassium is influenced by aldosterone. Chloride movements follow sodium. Calcium is regulated by PTH and calcitonin, and phosphate regulation is opposite to calcium.

This chapter examines the critically important mechanisms for balancing the intake and output of bodily fluids, electrolytes, and maintaining acid-base balance, highlighting the needs of an athlete for constant fluid and electrolyte replacement.

Water is the largest single component of the body, varying by sex and body composition. Fluid is distributed into intracellular (ICF) and extracellular (ECF) compartments, with ECF further divided into interstitial fluid and intravascular fluid, alongside other specialized fluids.

Solutes in body fluids are classified as electrolytes (charged ions) or nonelectrolytes (covalent bonds). Electrolytes like sodium, potassium, chloride, and phosphate are crucial. Fluid movement between compartments occurs via capillary exchange and other transport mechanisms like facilitated diffusion and active transport.

The body uses chemical buffers (phosphate, protein, carbonic acid-bicarbonate systems) for short-term pH stability. Physiological buffers (lungs and kidneys) are crucial for long-term pH balance and compensating for imbalances. The carbonic acid-bicarbonate system is key in ECF, and protein buffers are most abundant.

Metabolic acidosis and alkalosis, and respiratory acidosis and alkalosis, are discussed. Each imbalance has specific causes and compensatory mechanisms involving the lungs (hyper/hypoventilation) and kidneys (reabsorption/secretion of bicarbonate and hydrogen ions).

Various disorders like edema and symptoms of acidosis and alkalosis are presented. Homeostatic imbalances for electrolytes like sodium, potassium, phosphate, chloride, calcium, magnesium, and protein can lead to significant health issues. A chart is provided for analysis of acid-base conditions.