Chapter 10 Skeletal Muscle Tissue

Vocabulary flashcards covering key terms and definitions from Chapter 10: Skeletal Muscle Tissue.

Contractility

The ability of muscle tissue to contract forcefully when stimulated.

Excitability

The ability of muscle cells to respond to nerve signals or other stimuli with electrical impulses.

Extensibility

The ability of muscle tissue to be stretched beyond its resting length.

Elasticity

The ability of muscle tissue to recoil and return to its resting length after being stretched.

Sarcolemma

The plasma membrane of a muscle cell.

Sarcoplasm

The cytoplasm of a muscle cell.

Sarcoplasmic reticulum

Elaborate smooth endoplasmic reticulum in a muscle fiber that stores Ca2+.

Terminal cisterns

Enlarged regions of the sarcoplasmic reticulum that store Ca2+ at the A-I junctions.

T tubules

Deep invaginations of the sarcolemma that conduct impulses into the muscle fiber.

Triad

A T-tubule flanked by two terminal cisterns at the A-I junction.

Myofibril

Rodlike contractile organelle composed of sarcomeres; forms most of the muscle fiber’s volume.

Sarcomere

The basic contractile unit of a muscle fiber, from Z disc to Z disc.

Z disc

The boundary between adjacent sarcomeres where thin filaments anchor.

A band

Region of a sarcomere containing thick filaments; remains the same length during contraction.

I band

Region containing only thin filaments; shortens during contraction.

H zone

Central region of the A band where only thick filaments are present; disappears during contraction.

M line

Centerline of a sarcomere; anchors the thick filaments.

Thick filament

Myosin filaments; contain myosin heads and ATPase activity.

Thin filament

Actin filaments; paired with regulatory proteins troponin and tropomyosin.

Actin

The main structural protein of thin filaments; binds myosin during contraction.

Myosin

Motor protein of thick filaments; ATPase activity powers contraction.

Troponin

Regulatory protein with sites for actin, tropomyosin, and Ca2+; controls actin-myosin interaction.

Tropomyosin

Regulatory protein that blocks actin-myosin binding in the absence of Ca2+.

Titind

Elastic protein that anchors thick filaments and provides elasticity; resists overstretch.

Myofilament

Contractile protein filament (actin or myosin) that makes up the myofibrils.

Myosin heads

Globular projections on myosin that form cross-bridges with actin during contraction.

ATP

Energy molecule needed for muscle contraction; powers cycling of myosin heads.

ATPase

Enzyme in the myosin head that hydrolyzes ATP to provide energy for contraction.

Neuromuscular junction

Synapse between a motor neuron and a muscle fiber; initiates muscle contraction.

Acetylcholine (ACh)

Neurotransmitter released at the neuromuscular junction to stimulate contraction.

Acetylcholinesterase

Enzyme that breaks down acetylcholine in the synaptic cleft to stop stimulation.

Motor unit

A single motor neuron and all the muscle fibers it innervates; all fibers contract together.

Recruitment

Process of activating more motor units to increase muscle force.

Myoblasts

Embryonic mesoderm cells that fuse to form skeletal muscle fibers.

Satellite cells

Immature cells that can fuse with muscle fibers to aid growth and repair.

Dystrophin

Protein linking the cytoskeleton of a muscle fiber to the extracellular matrix; supports the sarcolemma.

Duchenne muscular dystrophy (DMD)

X-linked recessive disease caused by dystrophin deficiency; progressive muscle degeneration.

Utrophin

Related protein that can substitute for dystrophin functionally in some contexts.

Myofascial pain syndrome

Pain due to tight bands of muscle fibers and trigger points.

Fibromyalgia

Chronic widespread pain syndrome with fatigue and sleep disturbances; unknown cause.

Rhabdomyolysis

Disintegration of skeletal muscle leading to myoglobin release and potential kidney failure.

Myoglobin

Oxygen-binding pigment in muscle fibers that facilitates endurance but can cause issues if released in blood.

Slow oxidative fibers (SO)

Muscle fibers—aerobically fueled, high mitochondria and myoglobin, fatigue resistant; used for posture.

Fast glycolytic fibers (FG)

Glycolytic, fast-contracting fibers with little myoglobin; fatigue quickly; provide quick bursts of power.

Fast oxidative fibers (FO)

Intermediate fibers with both aerobic capacity and relatively fast contraction; fatigue resistant.

Sarcopenia

Age-related loss of skeletal muscle mass and strength; reversible with exercise.