Muscle Physiology Review

These flashcards cover essential vocabulary and definitions related to muscle anatomy and physiology, including muscle types, properties, functions, and the processes involved in muscle contraction and relaxation.

Skeletal Muscle

Attached to bones, striated, voluntary, and contracts rapidly but tires easily.

Smooth Muscle

Involuntary muscle found in the walls of hollow organs, non-striated, and has slow, sustained contractions.

Cardiac Muscle

Involuntary muscle that makes up the heart, branching, striated, and has intercalated discs.

Irritability

The ability of muscle fibers to receive and respond to a stimulus.

Contractility

The ability of muscle fibers to forcibly shorten when stimulated.

Extensibility

The ability of muscle fibers to stretch.

Elasticity

The ability of muscles to recoil and return to their resting length after being stretched.

Endomysium

Connective tissue layer that covers each muscle fiber.

Perimysium

Stronger connective tissue layer that wraps around fascicles of muscle fibers.

Epimysium

Connective tissue that surrounds the entire muscle.

Tendons

Connective tissues that attach muscle to bone.

Sarcolemma

The cell membrane of muscle cells.

Sarcoplasma

The cytoplasm of muscle cells, containing myofibrils and organelles.

Myofibrils

Contractile organelles found in muscle cells that run the length of the cell.

Z-line

Defines the boundaries of each sarcomere in muscle fibers.

A-band

Region of the sarcomere that contains both thick (myosin) and thin (actin) filaments.

I-band

Region of the sarcomere that contains only thin (actin) filaments.

H-zone

The region in the center of the A-band that contains thick filaments only.

Sliding Filament Theory

The process by which myosin heads bind to actin to pull actin filaments, shortening the sarcomere.

Troponin

A protein that, when bound to calcium, shifts tropomyosin to expose active sites on actin.

Tropomyosin

A protein that blocks the binding sites on actin, preventing contraction.

Calcium Ions

Essential for muscle contraction; bind to troponin to initiate cross-bridge formation.

Acetylcholine (ACh)

Neurotransmitter released at the neuromuscular junction to stimulate muscle contraction.

Neuromuscular Junction

The site where a motor neuron connects with a muscle fiber to initiate contraction.

ATP (Adenosine Triphosphate)

The energy currency required for muscle contractions; releases myosin head from actin after muscle contraction

Rigor Mortis

Postmortem stiffness of muscles caused by the lack of ATP which prevents cross-bridges from detaching.

Muscle Atrophy

The wasting away or decrease in size of muscle fibers due to disuse.

Muscle Hypertrophy

The increase in size of muscle fibers due to forceful, repetitive activity.

Creatine Phosphate

A compound that helps produce ATP quickly during short bursts of intense activity.

Oxygen Debt

The extra oxygen needed after exercise to restore metabolic conditions to resting levels.

Cellular Respiration

The process by which cells convert glucose and oxygen into ATP

Krebs Cycle

Generates ATP in the presence of oxygen

Glycolysis

The breakdown of glucose to pyruvic acid; does not require oxygen

Lactic Acid

A byproduct of anaerobic respiration (without oxygen) that can accumulate and lead to muscle fatigue.

Flexion

A movement that decreases the angle between bones.

Extension

A movement that increases the angle between bones.

Abduction

Movement away from the midline of the body.

Adduction

Movement toward the midline of the body.

Circumduction

Circular movement that combines flexion, extension, abduction, and adduction.

Rotation

Movement around a central axis of a joint.

Dorsiflexion

Movement that brings the toes closer to the shin.

Plantar Flexion

Movement that decreases the angle between the foot and the leg, pointing the toes downwards.

Inversion

Movement that tilts the sole of the foot inward, toward the midline of the body.

Eversion

Movement that tilts the sole of the foot outward, away from the midline of the body.

Supination

Rotational movement of the forearm that turns the palm upward.

Pronation

Rotational movement of the forearm that turns the palm downward.

Retraction

Movement of a body part backward, typically involving the shoulder blade or jaw.

Protraction

Movement of a body part forward, such as the shoulder blade or jaw.

Elevation

Movement of a body part upward, such as raising the shoulders.

Depression

Movement of a body part downward, such as lowering the shoulders.