Isotropic bands

In physiology, isotropic bands (better known as I bands) are the lighter bands of skeletal muscle cells (a.k.a. muscle fibers). The darker bands are called anisotropic bands (A bands). Together the I-bands and A-bands contribute to the striated appearance of skeletal muscle.

Isotropic bands indicate the behavior of polarized light as it passes through I bands. These are with low refractive index and they are isotropic to polarized light.