PAS 313: Muscle Histology Vocabulary Flashcards

A comprehensive vocabulary flashcard set for PAS 313: Human Anatomy Muscle Histology, covering muscle classifications, functional properties, anatomical organization, microscopic structures, sliding filament mechanics, neuromuscular junction dynamics, and skeletal muscle fiber types.

Skeletal Muscle

A muscle type attached to the skeleton that creates voluntary movement, characterized by long, multi-nucleated, and striated cells.

Smooth Muscle

An involuntary muscle type found in the walls of the gastrointestinal tract and blood vessels, composed of elongated cells with a single nucleus.

Cardiac Muscle

An involuntary muscle type found exclusively in the heart, consisting of uni-nucleated branching cells arranged end-to-end to pump blood.

Irritability

The characteristic property of muscle tissue that enables it to receive and respond to stimuli from neurons.

Contractility

The characteristic property of muscle tissue to respond to a stimulus by shortening or contracting.

Extensibility

The ability of muscle tissue to extend or stretch back to its original length following contraction.

Elasticity

The ability of muscle tissue to return to its desired original shape after being stretched.

Endomysium

The loose connective tissue layer that surrounds individual skeletal muscle fibers.

Fascicle

A bundle of multiple skeletal muscle fibers that is visible to the naked eye.

Perimysium

The layer of connective tissue that surrounds a muscle fascicle.

Epimysium

The dense layer of connective tissue that envelops the entire muscle belly.

Fascia

The outermost layer of connective tissue that separates skeletal muscle from surrounding structures.

Tendon

A dense regular connective tissue structure that connects a muscle to a bone.

Aponeurosis

A thin, broad sheet of dense regular connective tissue that attaches muscle to tissue or bone, such as the latissimus dorsi tendon.

Sarcolemma

The plasma membrane of an individual muscle cell, situated deep to the endomysium.

Sarcoplasm

The cytoplasm of a muscle cell, which contains mitochondria and muscle-specific organelles.

Myoglobin

An iron-containing red protein located within the sarcoplasm that stores oxygen.

Myofibril

A cylindrical subunit within a muscle fiber containing contractile protein structures that produce a striated appearance.

T-Tubule

An internal tube-like extension of the sarcolemma that conducts action potentials from the surface into the sarcoplasmic reticulum.

Sarcoplasmic Reticulum

The specialized smooth endoplasmic reticulum of a muscle fiber that stores and releases calcium ions.

Myofilaments

Protein structures within myofibrils, primarily composed of actin and myosin, that participate in contraction.

Actin

The protein that forms thin myofilaments within a sarcomere.

Myosin

The protein that forms thick myofilaments within a sarcomere.

Sarcomere

The repeating functional unit of contraction within a myofibril, extending from one Z line to the next Z line.

Sliding Filament Theory

The mechanism of muscle contraction wherein thin actin filaments slide past thick myosin filaments, resulting in the shortening of sarcomeres, myofibrils, and muscle fibers.

Neuromuscular Junction

The anatomical site of contact or synapse between a motor neuron and a skeletal muscle fiber.

Acetylcholine (ACh)

The neurotransmitter secreted by a motor neuron at the neuromuscular junction to trigger an action potential in the muscle fiber.

Tetanus

A clinical condition caused by a bacterial toxin from Clostridium tetani that blocks contraction-inhibiting neurotransmitters in the spinal cord, leading to sustained, involuntary muscle rigidity and spasms.

Motor Unit

A functional unit consisting of a single motor neuron and all the individual muscle fibers it innervates.

All-or-Nothing Principle

The physiological rule stating that when a single motor neuron is activated, every muscle fiber in its motor unit contracts to its maximum capability.

Red Slow-Twitch Fibers

Fatigue-resistant skeletal muscle fibers that contract slowly with low force, relying on aerobic metabolism, high myoglobin content, and numerous mitochondria.

White Fast-Twitch Fibers

Skeletal muscle fibers specialized for rapid movement and high force that fatigue quickly, relying on anaerobic metabolism, low myoglobin, and large glycogen reserves.

Intermediate Fast-Twitch Fibers

Skeletal muscle fibers that generate fast, moderate force with moderate-to-high fatigue resistance, utilizing aerobic metabolism along with some glycogen reserves.

Skeletal Muscle Fiber Histology (Cross Section)

A cross-sectional histological stain showing dark slow-twitch fibers containing high myoglobin/mitochondria and lighter fast-twitch fibers.