Muscle Physiology

Skeletal Muscle

Muscle tissue that is striated and under voluntary control, composed of bundles called fascicles.

Fascicles

Bundles of muscle fibers within skeletal muscle.

Myofibrils

Muscle cells within fibers that contain the contractile elements of muscle.

Contractility

The ability of muscle cells to shorten or contract.

Excitability

The ability of muscle cells to respond to stimuli.

Extensibility

The ability of muscle cells to be stretched without damage.

Elasticity

The ability of muscle cells to return to their original length after stretching.

Sarcomere

The basic functional unit of a muscle cell, responsible for muscle contraction.

Sliding Filament Model

Theory that muscle contraction occurs by myosin heads pulling actin filaments toward the center of the sarcomere.

Neuromuscular Junction

The synapse or junction between a motor neuron and a skeletal muscle fiber.

Twitch

A single contraction-relaxation cycle of a muscle.

Isometric Contraction

Muscle contraction without a change in muscle length while producing tension.

Isotonic Contraction

Muscle contraction that results in a change in muscle length while maintaining constant tension.

Phasic Contraction

A rapid contraction of muscle.

Tonic Contraction

A slow, controlled contraction and relaxation of muscle.

Intercalated Discs

Specialized connections between cardiac muscle cells containing gap junctions.

Reflex

A rapid, automatic response to a stimulus.

SAME DAVE

sensory/dorsal, afferent, ventral, and efferent in spinal cord reflexes.

Fast Glycolytic Muscles

Muscle fibers that contract quickly and rely on anaerobic glycolysis for energy, characterized by poor fatigue resistance.

Slow Oxidative Muscles

Muscle fibers that contract slowly, using aerobic respiration for energy, characterized by high fatigue resistance.

Fast Oxidative Muscles

Muscle fibers that contract quickly and utilize aerobic respiration, characterized by moderate fatigue resistance.