Ooh my little filaments, filaments --
Actin and myosin myofibrils:
Proteins that are long and dense, long and dense,
Making up the structure of the myofibrils.

CHORUS:
Signal from the brain rides the nerve to the muscle,
Where the myosin inside will slide past the actin of the
My-my-my-y-y, woo! Muh-muh-muh-myofibrils.

Add a little calcium, calcium
To the cytoplasm near the myofibrils.
It will turn troponin on, troponin on,
Causing the contraction of the myofibrils.

CHORUS

Muscles need energy, energy,
Most of which is needed by the myofibrils.
Myosin burns ATP, ATP
Fueling the contractions of the myofibrils.

CHORUS