Structure and Function of Skeletal Muscle Fibers

These flashcards cover key terms and concepts related to the structure and function of skeletal muscle fibers, essential for understanding muscle physiology.

Skeletal Muscle Fiber

Individual muscle cells that are long and cylindrical, formed from the fusion of multiple myoblasts and contain multiple nuclei.

Endomysium

A thin connective tissue layer that surrounds each individual skeletal muscle fiber.

Fascicle

A bundle of skeletal muscle fibers that are grouped together by connective tissue perimysium.

Epimysium

The outer fibrous connective tissue wrapping that encloses all fascicles within a muscle.

Sarcoplasm

The cytoplasm of a muscle cell (myocyte).

Sarcoplasmic Reticulum (SR)

Modified endoplasmic reticulum in muscle fibers that stores and releases calcium ions.

Myofibrils

Cylindrical organelles in muscle fibers made up of bundles of specialized proteins that allow for muscle contraction.

Transverse Tubules (T-tubules)

Deep inward extensions of the sarcolemma, filled with extracellular fluid, that help propagate action potentials into muscle fibers.

Triad

Structure formed by two terminal cisternae and a corresponding T-tubule in a muscle fiber.

Myofilaments

Filaments within myofibrils, including thick, thin, and elastic filaments, responsible for muscle contraction.

Thick Filaments

Myofilaments made primarily of myosin that produce tension during contraction.

Thin Filaments

Myofilaments composed mainly of actin, tropomyosin, and troponin that play a key role in muscle contraction.

Elastic Filaments

Composed of titin, these myofilaments stabilize the myofibril structure and provide elasticity.

Sarcomere

The functional contractile unit of a muscle fiber, extending from one Z disc to another.

Action Potential

A brief, temporary change in the membrane potential of a cell, critical for muscle contraction.

Resting Membrane Potential

The electrical potential across the sarcolemma of a resting muscle fiber, approximately -90 mV.

Ion Channels

Proteins in the plasma membrane that allow ions to move in and out of the cell, essential for action potentials.

Depolarization

The phase of an action potential where the membrane potential becomes less negative, primarily due to sodium influx.

Repolarization

The phase of an action potential where the membrane potential returns to a more negative value, primarily due to potassium efflux.