Contraction of Skeletal Muscle

Myocyte

A long, multinucleated muscle cell responsible for contraction.

Contains myofibrils, which are made up of contractile proteins

Sarcolemma

The plasma membrane of the muscle cell, which helps conduct electrical signals for contraction

T-Tubules

Extensions of the sarcolemma that help transmit electrical impulses deep into the muscle cell

Sarcoplasmic Reticulum

The SR restores and releases calcium ions, which are essential for muscle contraction

Sarcoplasm

The cytoplasm of the muscle cell, containing energy sources and proteins

Myofibrils

Rod-like structures inside the muscle fiber

Made of contractile proteins and regulator proteins, which enable contraction

Sarcomere

The functional unit of muscle contraction

Composed of overlapping actin and myosin filaments

Repeats throughout the myofibrils, giving muscle its striated appearance

Thick Filaments

Are composed of strands of the protein myosin

Thin Filaments

Are composed of strands of the protein actin

A band

Is dark and it contains thick filaments mostly myosin

H band

Light area at center of the A band and the area where actin and myosin don’t overlap

I band

Is light and contains thin filaments mostly only actin

Alpha Actinin

(Structural proteins), binds actin to Z line

Titin

(Structural proteins), connects Z line to M line. Provides muscle with its elasticity

Nebulin

(Structural protein), helps align actin molecules in the actin filament

Myomesin

(Structural protein), M line, this binds to fibrils and connects adjacent thick filaments to one another

Myosin FIlament

Made up of 200 or more individual molecules, with the tails bundled together and the heads hanging outward. The cross-bridges are flexible at two points, allowing the heads to be either extended far outward from the body or brought close to the body.

Adenosine Triphosphatase (ATPase)

Another feature of the myosin head that is essential for muscle contraction is that it functions as a what enzyme?

Actin Filament

• A double stranded protein

• Formed by polymerization of the globular protein

• Myosin binding site during muscle contraction

Tropomyosin

These molecules are wrapped spirally around the sides of the F-actin helix. In the resting state, this molecule lie on top of the active sites of the actin strands so that attraction cannot occur between the actin and myosin filaments to cause contraction

Fenn Effect

Large amounts of ATP are cleaved to form ADP during the contraction process, and the greater the amount of work performed by the muscle, the greater the amount of ATP that is cleaved; This phenomenon is called?