Muscles and Muscle Contractions

Muscle cells

Convert chemical energy (ATP) into kinetic energy

Smooth Muscles

Long, tapered cells arrange in parallel lines forming sheets. Contract involuntarily, non striated, single nucleus, contracts slowly but can stay contracted for prolonged periods of time without fatigue. Found in artery walls and internal organs

Cardiac Muscle

Striated, tubular, and dark. Each cell has a single nucleus. Contract involuntarily, found in walls of the heart

Skeletal Muscles

Striated and tubular muscles. Have many nuclei, and contract voluntarily. Cells are often called muscle fibres because of their length. Found attached to bones.

Muscles

An organ surrounded by connective tissue and composed of several tissues, largest unit, attached to bone by tendons

Muscle-Fibre Bundles

Large number of muscle fibres bundled together and wrapped in connective tissue, blood vessels and nerves run between the bundles

Myofibrils

Hundreds and thousands of cylindrical subunits that make up muscle fibers

Myofilaments

Protein structures responsible for muscle contraction.

Actin

Myofilament, thin filament. Consists of two molecules wrapped around each other.

Myosin

Myofilament, thick filament. Consists of two proteins wrapped around each other, but 10x longer than an actin filament. One end consists of a long rod, the other end has a double-headed globular region

Sarcomere

Functional unit of a muscle, composed of many myofilaments

Myogoblin

Oxygen-binding pigment; stores oxygen for muscle contractions

Sarcolemma

Membrane of muscle fibre; regulates entry and exit of materials

Sarcoplasm

Cytoplasm of muscle fibre; site of metabolic processes; contains myoglobin and glycogen

Sarcoplasmic Reticulum

Smooth ER in muscle fibre; stores calcium ions

H Zone

Shows myosin. Shortens during contraction.

A Band

Shows an overlap of actin and myosin. Dark band, stays the same during contraction

I Band

Shows just actin. Light band, shortens during contraction

X Line

Divide one sarcomere from another. Pulled closer together when a muscle contracts