Question

Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Answer 1

Sarcomere is the structural and functional unit of a myofibril in a skeletal muscle fibre. It is the segment of the myofibril between two successive Z lines.

A sarcomere shows alternating dark and light bands due to the arrangement of actin and myosin filaments.

Different regions of a sarcomere are:

Z line. This is the boundary of the sarcomere. Thin actin filaments are attached to the Z line.

I band. This is the light band. It contains only thin actin filaments.

A band. This is the dark band. It contains thick myosin filaments and overlapping actin filaments.

H zone. This is the lighter central region of the A band. It contains only thick myosin filaments.

M line. This is present at the centre of the sarcomere. It holds the thick myosin filaments together.