GLOSSARY

The levels of structural organization describe the hierarchical arrangement of the body’s components, from the simplest to the most complex level.
Each level is built from units of the level below and acquires new properties.

Six Main Levels

• Chemical level: atoms and molecules, such as ATP and the proteins actin and myosin.
• Cellular level: cells, such as a muscle fiber.
• Tissue level: groups of similar cells, such as skeletal muscle tissue.
• Organ level: several tissues forming an organ, such as the biceps brachii with its muscle, connective, and nervous tissue.
• Organ system level: organs working together for a common purpose, such as the muscular system.
• Organismal level: the whole human body.

Relevance to Sport

A strength training session acts on every level: protein synthesis rises at the chemical level, fibers grow at the cellular level, the muscle becomes stronger at the organ level, and at the organismal level the athlete lifts a heavier weight.

Key Teaching Point

These levels are the roadmap of this encyclopedia; its topics also start with the cell and tissues and lead on to the body systems.