Anatomy & Physiology
Core concepts
Eight ideas that explain every body system, from homeostasis to flow down gradients, with every place each one appears in the course.
- HomeostasisSensors, a control center and effectors hold a regulated variable near a set point, mostly by negative feedback.
- Flow down gradientsBlood, air, ions, water and heat all move from high to low pressure, concentration, voltage or temperature, at a rate set by the gradient and the resistance.
- Cell-to-cell communicationCells coordinate through electrical signals, chemical messengers and direct connections; a signal acts only on cells that carry its receptor protein.
- Structure and functionWhat a structure can do follows from its shape and parts, from molecules to whole organs.
- Mass balanceThe amount of any substance in the body changes only by what enters, leaves, is made or is used up.
- Energy and ATPCells capture energy from food as ATP and spend it on pumping, moving and building.
- Membranes and compartmentsMembranes divide the body into compartments with different contents, and control what crosses between them.
- Interdependence of systemsNo system works alone: a change in one system is sensed and answered by others.