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Skeletal muscle

Voluntary muscle attached to bones that produces movement.

Cardiac muscle

Involuntary muscle that makes up the heart.

Smooth muscle

Involuntary muscle found in organs and blood vessels.

Epimysium

Fascia that covers entire muscle.

Perimysium

Fascia that surrounds bundles of muscle fibers (fascicles).

Endomysium

Fascia that surrounds individual muscle fibers.

Plasmalemma folds

Shallow folds that increase surface area and help distribute force during muscle contraction.

Tendon

Structure that the plasmalemma fuses with at the end of the muscle fiber to transmit force from muscle to bone.

Satellite cells

Muscle stem cells located between the sarcolemma and basal lamina that aid in muscle repair, growth, and regeneration.

T-tubules

Extensions of the plasmalemma that carry action potentials deep into the muscle fiber and trigger calcium release.

Myofibrils

Structures made up of repeating units called sarcomeres, containing actin (thin filaments) and myosin (thick filaments).

Sarcomere

Basic unit of a muscle, consisting of actin and myosin organized in a specific structure.

Functions of skeletal muscle

Produce movement, maintain posture, stabilize joints, generate heat, store nutrients.

Calcium in contraction

Calcium released from the sarcoplasmic reticulum binds to troponin, moving tropomyosin to allow myosin to bind actin.

Nebulin

Protein that stabilizes actin filaments and regulates thin filament length.

Excitation–Contraction Coupling

Process starting with motor neuron release of acetylcholine, leading to an action potential and subsequent muscle contraction.

ATP in contraction

Provides energy for the power stroke, detaches myosin from actin, and powers calcium pumps.

Type 1 Fibers

Muscle fibers that are slower and use aerobic metabolism.

Type 2 Fibers

Muscle fibers that are faster and use anaerobic metabolism.

Size Principle

The principle stating that smaller motor units (Type 1) are recruited first, followed by larger units (Type 2) as force increases.

Grading muscle force

Accomplished through motor unit recruitment and rate coding (frequency of stimulation).

Muscle memory mechanisms

Includes myonuclear addition and epigenetic changes that facilitate faster retraining after detraining.