Muscle Tissue and Skeletal Muscle Structure

Vocabulary practice flashcards covering muscle tissue types, functional properties, connective tissue wrappings, and the structural organization of skeletal muscle fibers and sarcomeres.

Contractility

The unique ability of muscle tissue to shorten in length, generating physical force to create motion.

Extensibility

The property of a muscle that allows it to extend or stretch beyond its normal resting length.

Elasticity

The ability of muscle tissue to return to its original resting shape after being stretched beyond normal means.

Thermogenesis

The production of body heat through muscular contractions, primarily generated by skeletal muscle contractions to maintain body temperature.

Sphincter

A muscular ring that seals off and compartmentalizes internal body spaces, such as the digestive and urinary tracts, to store substances.

Tendon

A structure made of dense regular connective tissue formed by extensions of muscle fascia that anchors a skeletal muscle to bone.

Origin

The fixed, immovable attachment point of a muscle from which force is transferred during contraction.

Insertion

The movable attachment point of a muscle that is pulled toward the origin when the muscle contracts.

Epimysium

The outermost layer of connective tissue fascia that completely wraps around an entire skeletal muscle.

Perimysium

The connective tissue layer that groups individual skeletal muscle fibers into bundles called fascicles.

Fascicle

A bundle of skeletal muscle fibers wrapped together by perimysium within a muscle.

Endomysium

The innermost layer of connective tissue that directly encloses an individual skeletal muscle fiber.

Skeletal muscle fiber

A long, thin, fibrous, multinucleated skeletal muscle cell that can reach up to approximately $30\,\text{cm}$ in length.

Neuromuscular junction

The specific region where a somatic motor neuron meets a muscle fiber to transfer electrical action potentials to the muscular system.

Aponeurosis

A thick sheet of fascia that attaches two muscle bellies together, enabling them to contract in unison.

Sarcomere

The basic functional unit of a skeletal muscle fiber, demarcated from one Z disc to the next, where shortening and motion originate.

Sarcolemma

The phospholipid bilayer cell membrane covering the outer boundary of a skeletal muscle fiber.

Sarcoplasm

The specialized cytoplasm of a muscle fiber that surrounds and bathes the myofibrils.

Transverse tubules (T tubules)

Inward tunnel-like extensions of the sarcolemma that project across the transverse plane into the interior of the muscle fiber.

Sarcoplasmic reticulum

A net-like intracellular organelle surrounding myofibrils whose primary job is to store intracellular calcium for muscle contraction.

Terminal cistern

An expanded segment of the sarcoplasmic reticulum situated adjacent to a transverse tubule.

Myofibril

A rod-like contractile organelle located within a skeletal muscle fiber, constructed from repeating protein filaments.

Myosin

The primary contractile protein that forms thick filaments, which is anchored at the M line and pulls on thin filaments during contraction.

Actin

The primary contractile protein that forms thin filaments, which is anchored directly to the Z discs of a sarcomere.

Z disc

A zigzag protein boundary defining the outer ends of a sarcomere where thin actin filaments are anchored.

M line

The structural center of a sarcomere containing the protein myomesin, which holds thick myosin filaments in place.

Contractile proteins

Proteins, specifically actin and myosin, directly responsible for binding together to generate mechanical force in a sarcomere.

Regulatory proteins

Proteins including troponin and tropomyosin that act as the on/off switch to permit or inhibit muscle contraction.

Structural proteins

Proteins that maintain the precise alignment of thick and thin filaments and help re-lengthen the sarcomere to reset it after contraction.