Anatomy & Physiology
A practical map of the body's structures and systems
Lesson 1 of 20
Organization & homeostasis
The body is organized from molecules to a coordinated whole. Each level contributes to the next, while organ systems cooperate to maintain conditions compatible with life. Homeostasis is dynamic regulation, not a perfectly fixed state. Feedback loops adjust processes as internal or external conditions change.
Key points
- Chemical components form cells, the smallest living structural units.
- Similar cells form tissues; tissues combine into organs.
- Organs cooperate in systems, and systems sustain the organism.
- A receptor detects change, a control center compares it with a target, and an effector responds.
- Negative feedback reverses a deviation; positive feedback amplifies a process until an endpoint.
- Temperature regulation and blood glucose control are common negative-feedback examples.
Key terms
- Homeostasis
- Dynamic maintenance of a relatively stable internal environment.
- Negative feedback
- Response that reduces the initial deviation from a regulated range.
- Positive feedback
- Response that increases a process until a defined endpoint.
- Receptor
- Sensor that detects a change in a condition.
- Effector
- Structure that carries out a regulatory response.
Memory tip
Think: cells build tissues, tissues build organs, systems support the person.
Clinical note
Massage may influence comfort and perceived stress, but it does not replace medical care or regulate disease on demand.
Unit checkpoint
Lock it in: match the terms, then test yourself.