1. Muscle and Muscle Contraction

4. The functional unit of muscle is the sarcomere.

6. Muscle Proteins
Actin – a globular protein polymerized to form a double-stranded coil
Tropomyosin is positioned in the groove of the actin
Myosin heavy chains form double coiled strands with a bipolar head
Myosin light chains associate with the heavy chains and regulate activity
Troponin – a cluster of globular proteins associates with the tropomyosin

10. Sliding Filament Theory
When muscle contracts, sarcomeres shorten as the filaments slide over one another, but the actin and the myosin do not shorten