The Muscular System

Muscles are responsible for all types of body movement

All muscles share some terminologyPrefixes myo and mys refer to “muscle”Prefix sarco refers to “flesh”

What are the 3 types of muscle tissue?

Connective Tissue Wrappings of Skeletal Muscle

– Endomysium—encloses a single muscle fiber

–Perimysium—wraps around a fascicle (bundle) of muscle fibers

– Epimysium—covers the entire skeletal muscle

– Fascia—on the outside of the epimysium

(This is the tough layer you will need to break through to separate one muscle from another during the chicken

leg dissection)

–Muscle fiber = Muscle cell

Connective Tissue Wrappings of Skeletal Muscle

Microscopic Anatomy of Skeletal Muscle

Sarcolemma—specialized plasma membraneMyofibrils—long organelles inside muscle cellI band – light bandA band- dark band

Sarcomere—contractile unit of a muscle fiberOrganization of the sarcomere

MyofilamentsThick filaments = myosin filamentsThin filaments = actin filaments

The Sliding Filament Theory of Muscle Contraction

The Sliding Filament Theory of Muscle Contraction

• Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the actin (thin) filament

• Myosin heads pull the actin toward the center of the sarcomere

Actin

Myosin

Head

• This continued action causes a sliding of the myosin along the actin

• The result is that the muscle is shortened (contracted)

• Animation