- isotropic band is designated the I band;
- this is composed of thin filaments - composed only of actin;
- at higher magnification, each I band is bisected by a dark line, Z line;
- a sarcomere, extends between two successive Z lines & is approximately 2.2 long in resting muscle.
- w/ max contraction, sarcomere shortens 20-50% of its nl resting length.
- I band becomes shorter & H zone usually disappears.