The myosin head moves toward the M line, pulling the actin along with it. Sarcomere Structure To understand the sliding filament model requires an understanding of sarcomere structure. This reaction is catalyzed by the enzyme creatine kinase and occurs very quickly; thus, creatine phosphate-derived ATP powers the first few seconds of muscle contraction.
Other actions such as locomotion, breathing, and chewing have a reflex aspect to them: the contractions can be initiated both consciously or unconsciously.
However, thick and thin filaments—the components of sarcomeres—do not shorten. If the muscle is stretched to a point the tension will increase in the muscle. This is an electrical event, called an action potential, that can be used as a cellular signal.
This zone where thin and thick filaments overlap is very important to muscle contraction, as it is the site where filament movement starts. When eccentric contractions are used in weight training, they are normally called negatives.
The breakdown of one glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or when oxygen levels are low, converted to lactic acid Figure 5 b.
On the other hand, when picking up a piano, the motor cortex signals all of the neurons in the biceps so that every myofiber participates.