Muscle Anatomy, Physiology, and Contraction Mechanisms

Epimysium

Fibrous connective tissue sheath that surrounds an entire muscle.

Fascicle

A bundle of skeletal muscle fibers.

Perimysium

A connective tissue sheath surrounding a fascicle.

Endomysium

Connective tissue sheath surrounding each muscle fiber and contains capillaries and nerves.

Fascia

Connective tissue sheath that compartmentalizes and separates muscle groups from the skin, adipose and other muscle groups.

Periosteum

Connective tissue membrane that covers the outer surface of all bones.

Tendons

Tough band of fibrous connective tissue that connects muscle to bone.

Sarcoplasm

Cytoplasm of a muscle cell.

Sarcoplasmic reticulum

ER but in muscle cells.

Myogenesis

Muscle development process.

Myoblasts

Embryonic cells that become muscle fiber.

Myocytes

Long, tubular cells that develop from myoblasts.

Oblique

At an angle.

Satellite cells

Cells in muscle fibers that promote their growth, repair, and regeneration.

Forms of actin

Filamentous actin or F-actin and Globular actin or G-actin.

Polymerization

Monomers combining chemically to form larger chains (polymers).

Cross bridge

Temporary bond between actin and myosin heads; this binding is calcium-dependent.

Titin

A protein responsible for the passive elasticity of the muscle that, along with myomesin, functions as a molecular spring.

Motor unit

One alpha motor neuron and all the muscle fibers it innervates.

Neuromuscular junction

A chemical synapse formed between an alpha motor neuron and a muscle fiber.

Acetylcholine (ACh)

Neurotransmitter released by alpha motor neuron.

Acetylcholinesterase

An enzyme that breaks down acetylcholine into acetic acid and choline.

Muscle twitch

Single contraction and relaxation cycle within a muscle fiber.

Wave summation

Addition of one twitch to another.

Tetanic contraction

Sustained muscle contraction caused by a motor neuron firing action potential at a very high rate.