Muscle Mechanics and Muscle Types

These flashcards cover key concepts related to muscle mechanics, types of muscle fibers, and their physiology.

Motor Unit

A motor neuron plus all skeletal muscle fibers it stimulates.

Tropomyosin

A contraction inhibitor that blocks myosin binding sites on actin molecules.

Excitation-Contraction Coupling

The process that requires Ca2+ and ATP to trigger muscle contraction.

Sarcoplasmic Reticulum

A structure in skeletal muscle cells that functions in calcium storage and release.

Twitch Contraction

Brief contractions of all muscle fibers in a motor unit in response to one action potential in the motor neuron.

Muscle Tone

The amount of activity that muscles have at rest, which disappears during REM sleep.

Length-Tension Relationship

The forcefulness of a muscle contraction depends on the length of sarcomeres before contraction.

Motor Unit Recruitment

The increase or decrease of the number of muscle fibers to produce total muscle tension.

Isometric Contraction

A contraction where no movement occurs, but tension is generated.

Isotonic Contraction

A contraction where a load is moved, including concentric and eccentric types.

Slow Oxidative Fibers

Red in color, these fibers have many mitochondria and are used for prolonged, sustained contractions.

Fast-Glycolytic Fibers

White in color, these fibers have fewer mitochondria and are used for anaerobic movements for short durations.

Cardiac Muscle

More sarcoplasm, larger transverse tubules, and limited intracellular Ca2+ reserves compared to skeletal muscle.

Smooth Muscle

Characterized by less developed SR, no striations, and slower contraction and relaxation times.

Regeneration of Muscle

Mature muscle cells can increase in size (hypertrophy) but do not divide; satellite cells retain limited regenerative ability.

Sarcopenia

Gradual loss of muscle mass that occurs with aging, particularly after the age of 30.

Calmodulin

A protein that plays a role in smooth muscle contraction, replacing troponin found in skeletal muscle.

Hypertrophy

Increase in muscle size as a result of cellular enlargement, not cell division.

Fibrosis

The process of scar formation that occurs when muscle fibers cannot adequately regenerate.