Anatomy Chapter 1

Transvers Tubules (T-Tubules)

a deep invagination of the sarcolemma, which is the plasma membrane of skeletal muscle and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.

Troponin

a globular protein complex involved in muscle contraction. It occurs with tropomyosin in the thin filaments of muscle tissue

Plasmalemma

a plasma membrane that bounds a cell, especially one immediately within the wall of a plant cell.

Actin

a protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cells.

Tropomyosin

The binding of the myosin heads to the muscle actin is a highly regulated process. The thin filament is made of actin, tropomyosin, and troponin. The contraction of skeletal muscle is triggered by nerve impulses that in turn stimulate the release of Ca2+.

Epimysium

a sheath of fibrous elastic tissue surrounding a muscle.

Muscle Fiber

A skeletal muscle fiber is surrounded by a plasma membrane called the sarcolemma, which contains sarcoplasm, the cytoplasm of muscle cells. A muscle fiber is composed of many fibrils, which give the cell its striated appearance. Skeletal muscles are sheathed by a tough layer of connective tissue called the epimysium.

Sarcoplasmic Reticulum

a specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells.

Sarcomere

a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band.

Endomysium

a wispy layer of areolar connective tissue that ensheaths each individual myocyte (muscle fiber, or muscle cell). It also contains capillaries and nerves. It overlies the muscle fiber's cell membrane: the sarcolemma.

Nebulin

an actin-binding protein which is localized to the thin filament of the sarcomeres in skeletal muscle. It is a very large protein (600-900 kDa) and binds as many as 200 actin monomers.

Myofibrils

any of the elongated contractile threads found in striated muscle cells.

Myosin

are a large superfamily of motor proteins that move along actin filaments, while hydrolyzing ATP. About 20 classes of myosin have been distinguished on the basis of the sequence of amino acids in their ATP-hydrolyzing motor domains.

Satellite Cells

precursors to skeletal muscle cells, able to give rise to satellite cells or differentiated skeletal muscle cells. They have the potential to provide additional myonuclei to their parent muscle fiber, or return to a quiescent state

Musculoskeletal System

provides form, support, stability, and movement to the body. It is made up of the bones of the skeleton, muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together

Sarcoplasm

the cytoplasm of striated muscle cells

Sarcolemma

the fine transparent tubular sheath that envelops the fibers of skeletal muscles.

Perimesium

the sheath of connective tissue surrounding a bundle of muscle fibers.

Fascicle

a bundle of structures, such as nerve or muscle fibers