Sliding FilamentTheory

How do muscles work…..

Muscle Cell Structure

Muscles are broken into smaller muscle fibers

muscle fibers are broken into smaller units called myofibrils

myofibrils are broken into smaller units called sarcomeres

Sarcomere Structure- units of muscle contraction

These are made up of alternating thick proteins filaments (myosin) and thin protein filaments (actin)

This pattern forms different zones as shown here

Close up look at Myosin & Actin

Myosin filaments contain “heads” Actin filaments contain binding sites ATP is necessary for the

contraction to occur

“Power Strokes” Actin filaments slide towards the

center of sarcomere when muscle contracts….. Away when it relaxes

Myosin heads attach to binding sites forming cross bridges

when activated the cross bridges tilt inward towards center in a short powerful stroke

Muscle Contraction

ATP is required for the “heads” to detach and move to the next binding site

A series of power strokes causes noticeable muscle contraction

with no ATP the myosin heads do not detach and RIGOR occurs