Sarcomere Anatomy and Muscle Contraction Vocabulary

Vocabulary flashcards covering key terms related to sarcomere structure, filaments, and muscle contraction mechanics.

Sarcomere

A contractile unit in a muscle cell that lines up end-to-end to generate force and cause movement when contracting.

Myosin

The thick filament in a muscle cell containing heads that reach out, bind to, and pull on actin.

Actin

The thin filament in a muscle cell that myosin heads bind to and pull on during contraction.

I band

The lighter region of the sarcomere where myosin is absent and only thin filaments are present.

A band

The dark region of the sarcomere where the thick filament (myosin) is present; stands for anisotropic.

Striations

The stripe-looking nature of skeletal muscle caused by alternating between the light I band and the dark A band.

H zone

The brighter region in the middle of the A band where only myosin is present and actin does not extend into; named from 'helle', the German word for brighter.

M line

The dark region located directly in the middle of the H zone.

Power stroke

The movement in muscle contraction where myosin reaches, grabs, and pulls on the actin filament.

Z disc

Also referred to as the Z line, a structure located on either side of the I band in the sarcomere.