ch 11 muscular tissue pt 1

Excitable (muscle tissue)

Muscle tissue has the ability to respond to stimuli.

Contractility

The ability of muscle tissue to shorten or contract.

Extensibility

The capability of muscle tissue to stretch.

Elasticity

The ability of muscle tissue to return to its original size or shape after stretching.

Myofiber

Another term for muscle cell.

Myocytes

Muscle cells that are much longer than typical cells and can be as long as 30 cm.

Striated muscle tissue

Skeletal muscle tissue that appears striped due to the regular pattern of protein strands.

Mesoderm

The middle layer of embryonic tissue that forms muscle tissue.

Myoblasts

Precursors to myocytes that arise from the mesoderm.

Satellite cells

Unspecialized cells outside the cell membrane of a myocyte that help with growth and regeneration.

Sarcolemma

The plasma membrane of a myocyte.

Sarcoplasm

The cytoplasm of a myocyte that stores glycogen and myoglobin.

Glycogen

A compound that stores fuel in the form of glucose, present in the sarcoplasm.

Myoglobin

A protein that stores oxygen for the myocyte, similar to hemoglobin.

Myofibrils

Bundles of protein strands within myocytes that contract to shorten the muscle.

Sarcoplasmic reticulum (SR)

A network of tubes covering myofibrils that stores calcium.

Terminal cisternae

Swollen sacs at the ends of the sarcoplasmic reticulum for storage.

Transverse tubules (T-tubules)

Structures that run vertically through the myocyte and connect the sarcolemma to the SR.

Myofilaments

Thin and thick protein strands that make up myofibrils.

Myosin

Thick myofilaments shaped like golf clubs; they are essential for muscle contraction.

Actin

Thin myofilaments that work with myosin during contraction.

Tropomyosin

Protein that regulates the action of actin by blocking binding sites.

Troponin

Protein that acts as a regulatory switch turning actin on or off.

Sarcomere

The contractile unit of a muscle cell, defined by Z-discs.

Z-disc (Z line)

The boundaries of a sarcomere where actin is anchored.

Titin

A protein that enables the muscle to recoil after contraction.

A bands

Regions where actin and myosin overlap in a sarcomere.

I bands

Regions that contain only actin filaments, appearing light.

H-band

Region in the sarcomere with only myosin filaments, darker than I bands but lighter than A bands.

Calcium release

Triggers a change in troponin shape, leading to muscle contraction.

Binding sites on actin

Unblocked when tropomyosin moves, allowing myosin heads to bind.

Sliding filament model

Describes how myosin pulls on actin filaments during contraction.

Bare zone

Part of the H-band where myosin filaments have no heads.

Contraction mechanism

The process where myosin heads bind to actin and pull, sliding the filaments.