Module 5 broad concepts

Here is the updated list without any commas in the definitions

Skeletal Muscle

Voluntary striated muscle tissue containing many nuclei per long cylindrical cell found attached to bones.

Cardiac Muscle

Involuntary striated muscle tissue containing one nucleus per branched cell found in the heart.

Smooth Muscle

Involuntary non-striated muscle tissue containing one nucleus per spindle-shaped cell found in organs and the stomach.

Epimysium

The outer connective tissue layer surrounding an entire whole muscle.

Perimysium

The connective tissue layer surrounding a package or bundle of fibers called a fascicle.

Endomysium

The connective tissue layer surrounding each individual single muscle fiber.

Fascicle

A bundle or package of individual muscle fibers.

Muscle Fiber

A single multinucleated muscle cell.

Myofibril

A cylindrical structure within a muscle fiber composed of repeating units called sarcomeres.

Sarcomere

The basic structural and contractile unit of a muscle fiber that extends from Z-line to Z-line.

Z-Line (Z-Disc)

The outer boundary ends of a sarcomere.

M-Line

The center or middle line of a sarcomere.

A-Band

The region of a sarcomere containing thick filaments that never changes length during muscle contraction.

H-Zone

The central region of an A-band that shrinks during contraction.

Actin

The thin protein filament within a sarcomere that slides during contraction.

Myosin

The thick protein filament with heads that grab actin to pull thin filaments during contraction.

Tropomyosin

A protein that covers the myosin-binding sites on actin when a muscle is at rest.

Troponin

A regulatory protein attached to tropomyosin in skeletal muscle that binds calcium to uncover actin binding sites.

Sliding Filament Theory

The mechanism of muscle contraction where thin filaments and thick filaments slide past one another without shortening.

Neuromuscular Junction

The site or connection where a motor neuron communicates with a muscle fiber.

Acetylcholine (ACh)

The neurotransmitter released by a motor neuron to trigger a muscle action potential.

Excitation-Contraction Coupling

The sequence of events converting an electrical nerve impulse into mechanical muscle contraction.

Sarcolemma

The plasma membrane surrounding a muscle fiber.

Sarcoplasm

The cytoplasm inside a muscle fiber cell.

Sarcoplasmic Reticulum (SR)

The specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium ions.

T-Tubule (Transverse Tubule)

Invaginations of the sarcolemma that conduct action potentials deep into the muscle fiber.

Terminal Cisternae

Enlarged regions of the sarcoplasmic reticulum adjacent to T-tubules.

Triad

A structural unit composed of one T-tubule flanked by two terminal cisternae.

Cross-Bridge Cycle

The repetitive attachment power stroke release and resetting of myosin heads onto actin during contraction.

Power Stroke

The step in the cross-bridge cycle where the myosin head pulls the actin filament toward the center of the sarcomere.

Adenosine Triphosphate (ATP)

The energy molecule required to cock the myosin head and detach it from actin.

Creatine Phosphate

The fastest initial source of ATP for muscle contraction lasting about 15 seconds.

Glycolysis

An anaerobic pathway that produces 2 ATP molecules and lactic acid per glucose without using oxygen.

Aerobic Respiration

An oxygen-dependent pathway in mitochondria that yields 32 ATP molecules for long-lasting energy.

Slow Oxidative Fibers

Red muscle fibers with many mitochondria and high oxygen capacity that are fatigue-resistant and used for endurance.

Fast Oxidative Fibers

Intermediate muscle fibers suitable for moderate activities like walking or jogging.

Fast Glycolytic Fibers

White muscle fibers designed for powerful short bursts of activity that fatigue quickly.

Concentric Contraction

An isotonic contraction where the muscle shortens while generating force.

Eccentric Contraction

An isotonic contraction where the muscle lengthens under tension.

Isometric Contraction

A muscle contraction where tension is generated without any movement or change in muscle length.

Hypertrophy

An increase in muscle size and fiber thickness resulting from increased exercise.

Atrophy

A decrease in muscle size and strength due to disuse.

Sarcopenia

The age-related loss of muscle mass and strength.

Calmodulin

The calcium-binding protein used in smooth muscle instead of troponin.

Myosin Light Chain Kinase (MLCK)

An enzyme activated by the calcium-calmodulin complex in smooth muscle to activate myosin.

Motor Unit

A single motor neuron and all the individual muscle fibers it innervates.

Myoblasts

Embryonic cells that fuse together during development to form a single multinucleated muscle fiber.

Myosatellite Cells

Stem cells located in muscle tissue that help repair damaged muscle cells.