During a contraction, the I bands and H zone of a sarcomere contract. The A bands remain unchanged.
The sarcomere itself will become shorter.The sarcomere will shorten.
The Sarcomere
The basic unit of muscular contraction; the sarcomere.
the distance from one Z line to the next
During muscle contraction the actin heads pull the sarcomere closed
Myofibrils The sarcomere is the unit of muscular contraction.
Actin
muscle relaxation
Dark
The myofibril is the basic muscle cell, within which is the sarcomere, the basic unit of muscle contraction.
M line