Physiological Activity: Core Processes That Sustain Life

Definition

Physiologic activity encompasses the integrated physical and chemical processes that maintain homeostasis and enable survival, growth, and reproduction in living organisms.

Ten Fundamental Physiologic Processes

1. Respiration: Gas exchange (O₂ in, CO₂ out) → cellular ATP production.
2. Digestion & Absorption: Mechanical/chemical breakdown of food → nutrient uptake.
3. Metabolism: Catabolism (energy release) + anabolism (biosynthesis); regulated by enzymes, hormones.
4. Circulation: Blood flow delivers O₂, nutrients, hormones; removes wastes.
5. Excretion: Renal (urine), hepatic (bile), pulmonary (CO₂), cutaneous (sweat).
6. Neural Regulation: Rapid electrical signaling; sensory, motor, autonomic, cognitive.
7. Endocrine Regulation: Hormonal coordination of growth, metabolism, reproduction, stress response.
8. Immune Defense: Innate + adaptive immunity; surveillance, pathogen clearance, memory.
9. Muscular Contraction: Movement, posture, thermogenesis, organ function (heart, gut, vessels).
10. Reproduction: Gametogenesis, fertilization, development, lactation.

Homeostasis: The Unifying Principle

All processes interact via feedback loops (negative/positive) to maintain stable internal conditions (pH, temperature, glucose, pressure, osmolarity) despite external changes.

Clinical Relevance

Disease = disruption of physiologic activity. Medicine aims to restore or compensate for lost function.