The A band is a term used to refer to the central an area within a sarcomere - see the diagram below.
A sarcomere is the repeating functional unit of "striped" or "striated" muscle. This is also known as "skeletal muscle", "voluntary muscle", and "cardiac muscle". Its striated (stripey) visual appearance is due to alternating (dark) A bands and (light) I bands.
The relative sizes of the H Zone, the A band, and the I band of sarcomeres are determind by, and provide information about, the state of contraction or relaxation of the muscle tissue of which the sacromere is a part.
Above: Diagram of the unit within a muscle cell that is known as a sarcomere
The A band is a relatively darker area within the sarcomere that extends along the total length of the thick filaments.
This section consists of short summaries about the structures that form the muscles of the body. This list is not exhaustive but is intended to be appropriate for students of A-Level Human Biology, ITEC courses in massage and related subjects, and other courses in health sciences. For more general information about muscles see the pages about:
This section is about the
anatomical structures of muscles.
- Anterior Muscles
- Posterior Muscles
- Facial Muscles
- Muscle Terminology (Definitions)
- 1. Structure of Muscle
- 2. Structure of Muscle Cells
- 3. Muscle Filaments
- 4. Sliding Filament Theory
- 5. Neuromuscular Junction
- 6. Actions at Neuromuscular Junction
- Types of Muscle Contractions
- Muscular Disorders
- Effects of exercise on muscles