Muscle Types and Contraction Mechanisms

Flashcards covering key concepts related to muscle types, structure, function, and contraction mechanisms.

Skeletal Muscle

Muscle type that is voluntary, striated, multinucleated, and attached to bones.

Cardiac Muscle

Involuntary muscle found in the walls of the heart, striated, and has a single central nucleus.

Smooth Muscle

Involuntary muscle located in the walls of hollow organs, non-striated, and spindle-shaped with a single central nucleus.

Myofibril

Long, threadlike structures inside myofibers made up of repeating units called sarcomeres.

Sarcomere

The basic unit of contraction in muscle fibers, composed of actin and myosin.

Actin

Thin filament in muscle cells that has tropomyosin wrapped around it.

Myosin

Thick filament in muscle cells that binds to actin during contraction.

Troponin

A protein complex on actin that binds calcium and moves tropomyosin.

Rigor Mortis

The stiffening of muscles after death due to lack of ATP production.

Motor Unit Recruitment

The activation of additional motor units to generate more muscular force.

Calcium's role in muscle contraction

Calcium enables binding between actin and myosin by moving tropomyosin away from binding sites.

Z-lines

Structures that are pulled closer together during muscle contraction, thus shortening the sarcomere.

ATP

A molecule that powers the contraction and relaxation of muscles.

Tropomyosin

A protein that wraps around actin, blocking myosin-binding sites when the muscle is at rest.

Neuromuscular Junction

The connection between a nerve and a muscle where neurotransmitters are released to initiate contraction.

Power Stroke

The action where myosin heads pull actin filaments toward the center of the sarcomere during contraction.