Muscle Physiology Terminology

These flashcards cover key vocabulary terms related to muscle physiology, aiding in understanding essential concepts.

Epimysium

The outer connective tissue layer surrounding the entire muscle.

Perimysium

Connective tissue surrounding a fascicle (bundle of muscle fibers).

Endomysium

Connective tissue surrounding individual muscle fibers.

Fascicle

A bundle of muscle fibers.

Sarcoplasm

Gelatin-like substance filling the space between myofibrils (cytoplasm of the muscle cell).

Sarcoplasmic Reticulum (SR)

The storage site for calcium ions, essential for muscle contraction.

Sarcomere

The basic functional unit of a myofibril/muscle tissues, defined by Z discs.

Myosin (Thick Filament)

The thick filament within the sarcomere that contains myosin heads.

Actin (Thin Filament)

The backbone of the thin filament in the sarcomere.

Troponin

The site on the thin filament responsible for calcium binding, initiating contraction.

Resting Membrane Potential

The membrane voltage of a muscle fiber at rest, typically -70 mV.

Action Potential Peak

The peak voltage reached during muscle impulse transmission, typically +30 mV.

Motor Unit

A single alpha-motor neuron and all the muscle fibers it innervates.

Excitation-Contraction Coupling

The complex sequence of events triggering a muscle fiber to contract, beginning with motor nerve excitation and ending with muscle fiber contraction.

Sliding Filament Theory

Explains muscle contraction through the sliding of actin and myosin filaments over each other, resulting in muscle shortening.

Golgi Tendon Organs

Sensory receptors that signal muscles to relax when there is excessive tension.

Muscle Spindles

Sensory receptors that signal muscles to contract when there is excessive stretch.

Type I Fibers

Slow-twitched muscle fibers (110 ms to peak tension) characterized by slow ATPase activity and smaller alpha motor neurons.

Type II Fibers

Fast-twitched muscle fibers (50 ms to peak tension) characterized by fast ATPase activity and more developed SR.

Size Principle of Motor Unit Recruitment

The order of recruitment: Type I → Type IIa → Type IIx, meaning smaller motor units are recruited first.

Concentric Contraction

A type of muscle contraction where the muscle shortens (e.g., elbow flexion by biceps).

Eccentric Contraction

A type of muscle contraction where the muscle lengthens while exerting force (e.g., lowering a weight).

Isometric Contraction

A type of muscle contraction where force is generated without changing muscle length.

Hypertrophy

Increase in muscle fiber size through training, enhancing satellite cell numbers and fiber size.

Atrophy

Reduction in muscle fiber size due to disuse; nuclei may undergo apoptosis.