Explain the mechanism of muscle contraction with diagram

Mechanisms of muscle contraction:

There are many different concepts which are used to explain the process of muscle contraction. There is a contractile unit of the muscle which is called as the sarcomere. The sarcomere is composed of two types of filaments, myosin and actin. These filaments during contraction slide over one another. During contraction, the length of A-band remains constant and the length of I-band changes. As a result, the Z discs are pulled together. This leads to the contraction of the muscle. ATP as the source of energy for contraction. The ATP molecules binds to the myosin head and then gets attached to the actin filament and help in contraction.

Initiation of muscle contraction: Initiation of contraction of skeletal muscle starts with the generation of action potential in the muscle fibres. These elicit electrical currents due to which Ca ions are released. The Ca ions initiate the chemical events of the contractile process. This overall process of controlling muscle contraction is called excitation.