Ch. 9

Skeletal Muscle

Muscle that is attached to bones, under voluntary control, and responsible for movement.

Cardiac Muscle

Involuntary muscle that makes up the heart and is responsible for pumping blood.

Smooth Muscle

Involuntary muscle found in the walls of internal organs, such as the digestive tract.

Fascia

Thin covering of connective tissue around a muscle.

Tendon

Cord-like mass of connective tissue that connects muscle to a bone.

Aponeurosis

Sheet-like mass of connective tissue that connects a muscle to bone, skin, or another muscle.

Epimysium

Connective tissue that surrounds the whole muscle.

Perimysium

Connective tissue that surrounds fascicles within a muscle.

Endomysium

Connective tissue that surrounds muscle fibers within a fascicle.

Myofibrils

Long, parallel structures in muscle fibers that consist of thin actin filaments and thick myosin filaments.

Sarcomere

Functional unit of a muscle fiber that connects end-to-end to form myofibrils.

Sarcoplasmic Reticulum (SR)

Type of endoplasmic reticulum in muscle fibers that stores calcium ions.

Transverse Tubule

Structure that relays electrical impulses to the sarcoplasmic reticulum.

Neuromuscular Junction (NMJ)

The site where a motor neuron interacts with a muscle fiber.

Acetylcholine (ACh)

Neurotransmitter that stimulates muscle contraction.

Muscle Fatigue

Inability to contract effectively due to various factors, including lactic acid buildup.

Excitation-Contraction Coupling

The process that connects muscle fiber stimulation to muscle contraction.

Sliding Filament Model

Theory that explains muscle contraction as the sliding of thin and thick filaments past each other.

Isotonic Contraction

Muscle contraction that changes length while maintaining tension.

Isometric Contraction

Muscle contraction that does not change length but increases tension.

Slow-Twitch Fibers

Type I muscle fibers that are slower to contract and resistant to fatigue.

Fast-Twitch Fibers

Type II muscle fibers that contract quickly but fatigue rapidly.