Muscular System

Muscular System

System responsible for body movement, posture, and heat production.

Skeletal Muscle

Voluntary, striated muscle attached to bones.

Smooth Muscle

Involuntary, non-striated muscle in organs and vessels.

Cardiac Muscle

Involuntary, striated muscle found in the heart.

Epimysium

Connective tissue covering an entire muscle.

Perimysium

Connective tissue surrounding a muscle fascicle.

Endomysium

Connective tissue surrounding individual muscle fibers.

Myofibril

Long filamentous organelle within muscle cells containing actin and myosin.

Sarcomere

The functional unit of muscle contraction (Z-line to Z-line).

Actin

Thin protein filament in sarcomere.

Myosin

Thick protein filament in sarcomere.

Sliding Filament Theory

Explains how muscles contract by myosin sliding actin filaments.

Neuromuscular Junction

Connection between motor neuron and muscle fiber.

Acetylcholine (ACh)

Neurotransmitter that triggers muscle contraction.

Sarcoplasmic Reticulum

Stores and releases calcium for muscle contraction.

Calcium Ions

Trigger interaction between actin and myosin.

ATP

Energy molecule required for muscle contraction and relaxation.

Creatine Phosphate

Molecule that quickly regenerates ATP during contraction.

Aerobic Respiration

Energy production using oxygen; long-term.

Anaerobic Glycolysis

Energy production without oxygen; produces lactic acid.

Isotonic Contraction

Muscle shortens during contraction (e.g., lifting).

Isometric Contraction

Muscle tension increases, length stays same (e.g., plank).

Twitch

Brief, single muscle contraction.

Tetanus (Physiological)

Sustained, continuous contraction.

Muscle Tone

Slight, continuous contraction that maintains posture.

Agonist

Prime mover muscle responsible for a movement.

Antagonist

Muscle opposing the action of another.

Synergist

Muscle assisting a prime mover.

Fixator

Muscle that stabilizes the origin of a prime mover.

Origin

Point where muscle attaches to stationary bone.

Insertion

Point where muscle attaches to moving bone.

Flexion

Decreasing the angle between bones.

Extension

Increasing the angle between bones.

Abduction

Moving a limb away from the body.

Adduction

Moving a limb toward the body.

Rotation

Movement around an axis.

Circumduction

Circular movement of a limb.

Dorsiflexion

Bending foot upward.

Plantar Flexion

Pointing toes downward.

Supination

Turning palm upward.

Pronation

Turning palm downward.

Inversion

Turning sole of foot inward.

Eversion

Turning sole of foot outward.

Muscular Dystrophy

Genetic disorder causing muscle weakness.

Myasthenia Gravis

Autoimmune disease causing fatigue due to blocked ACh receptors.

Tetanus (Disease)

Bacterial infection causing continuous muscle spasms.

Cramps

Involuntary muscle contractions due to overuse or dehydration.

Strain

Muscle injury from overstretching or tearing fibers.