Sarcomere Structure and Contraction

Vocabulary based flashcards covering the anatomy of a sarcomere, including filaments and bands, and the physiological changes during muscle contraction.

Sarcomere

The smallest unit of a muscle to contract, bounded by Z lines.

Actin

The thin myofilament that looks like two strands of pearls and is attached to the Z line.

Myosin

The thick myofilament that has "hands" that bind to and pull actin during muscle contraction.

H zone

The part of a sarcomere containing only thick filaments (myosin) that shortens or disappears during contraction.

I band

The light band of a sarcomere containing only thin filaments (actin) that shortens when the muscle goes from relaxed to contracted.

Z line

The boundary between sarcomeres where actin is attached; these lines move closer together during contraction.

M line

The line running down the middle of the myosin filaments in a sarcomere.

A band

The dark band that runs the entire length of the myosin filament, containing both actin and myosin, and stays the same length during contraction.

Sliding Filament Theory Principle

The fact that when a sarcomere contracts, the actin and myosin filaments stay the same length while sliding past each other.

Actin Movement during Contraction

The process where actin moves closer to the M line as it is pulled by the myosin heads.