Physiology
Physiology is the study of how living bodies work, from cellular processes and organ systems to regulation, adaptation, health, disease, and daily function.
What physiology is
Physiology studies function in living organisms. It asks how cells communicate, how organs perform work, how body systems coordinate, and how organisms respond to internal and external change. Human physiology is central to health care, but the same kind of thinking also applies to animals, plants, microbes, and ecosystems of living processes.
Structure and function
Physiology is closely tied to anatomy because structure shapes function. The thin walls of air sacs support gas exchange, heart muscle is built for rhythmic contraction, nerve cells are shaped for signaling, and digestive surfaces are folded to increase absorption. A physiological explanation usually connects a body part to the job it performs.
Cells and energy
Every body system depends on cellular work. Cells move ions, build proteins, break down nutrients, communicate with neighbors, respond to signals, and use energy stored in chemical bonds. Metabolism links food, oxygen, enzymes, waste products, heat, and repair into the everyday activity of life.
Homeostasis and feedback
A major theme in physiology is homeostasis: keeping internal conditions within workable ranges. Body temperature, blood glucose, pH, fluid balance, blood pressure, oxygen, and calcium are regulated by feedback loops. These systems are dynamic, not static; they adjust constantly as a person eats, sleeps, exercises, grows, heals, or becomes ill.
Communication systems
The nervous and endocrine systems coordinate many body functions. Nerves can send fast electrical and chemical signals, while hormones often travel through the bloodstream and act over longer periods. Immune signaling, local chemical messengers, and cell-to-cell contact also help tissues coordinate responses to injury, infection, stress, growth, and repair.
Organ systems in action
Physiology becomes especially clear when systems work together. During exercise, muscles need more oxygen and fuel, breathing changes, the heart pumps more blood, vessels redirect flow, heat must be released, and hormones help manage energy. No organ system works as a sealed unit; function is coordinated across the whole body.
Adaptation, health, and disease
Physiological systems can adapt to training, altitude, pregnancy, fasting, infection, injury, aging, and medication. Disease often appears when regulation breaks down, tissues are damaged, or compensation is no longer enough. Understanding function helps explain symptoms, lab results, treatment effects, and why the same disease can affect people differently.
Why it matters
Physiology matters because it turns body facts into explanations. It helps people understand why a pulse changes, why fever happens, how medicines act, why dehydration affects thinking, how breathing and circulation connect, and why prevention or treatment can shift the body back toward workable function.