Fundamentals of Anatomy and Physiology - Muscle Tissue

Basic vocabulary of muscle tissue, covering types, structures, functions and associated proteins.

Skeletal Muscle

Striated muscle that is under voluntary control, attached to bones, and responsible for body movements.

Cardiac Muscle

Striated muscle found exclusively in the heart, involuntary, and has junctions called intercalated discs.

Smooth Muscle

Non-striated muscle found in the walls of hollow organs, involuntary, such as in blood vessels and the digestive tract.

Myoblasts

Embryonic cells that fuse to form muscle fibers.

Epimysium

Outermost connective tissue sheath that surrounds the entire muscle.

Fascicle

Bundle of muscle fibers segregated from the rest of the muscle by a connective tissue sheath.

Endomysium

Delicate connective tissue sheath that surrounds each individual muscle fiber.

Sarcomere

Functional unit of striated muscle, composed of thick and thin myofilaments.

G-actin

Globular actin, the monomeric subunit of the filamentous actin (F-actin).

Myosin

Thick filament protein that interacts with actin to cause muscle contraction.

Tropomyosin

Protein that covers myosin-binding sites on actin filaments in a resting muscle.

Sarcoplasmic Reticulum

Network of membrane-covered tubes that stores calcium ions needed for muscle contraction.

T-tubules

Invaginations of the plasma membrane that carry action potentials deep into the muscle cell.

Sliding Filament Model

Theory explaining muscle contraction where thin filaments slide over thick filaments.

ATPase

Enzyme activity of myosin heads that hydrolyzes ATP to provide energy for muscle contractions.

F-actin

Filamentous actin, composed of G-actin subunits arranged into a helical structure.

Myofibrils

Rod-like contractile elements that occupy most of the muscle cell; composed of sarcomeres.

Striations

The alternating light and dark bands seen in skeletal and cardiac muscle fibers due to the arrangement of myofilaments.