Chapter 10 – Muscle Tissue (BIOL 121, Westchester Community College)

Vocabulary flashcards covering key terms, structures, proteins, physiological processes, fiber types, energy systems, contraction mechanics, clinical conditions, and muscle tissue types discussed in the Chapter 10 lecture.

Myology

The scientific study of the muscular system.

Skeletal muscle

Voluntary, striated muscle tissue usually attached to bones.

Cardiac muscle

Involuntary, striated muscle of the heart with intercalated discs.

Smooth muscle

Involuntary, non-striated muscle found in walls of hollow organs and vessels.

Excitability

Ability of muscle to respond to chemical, stretch, or electrical stimuli.

Conductivity

Property by which a local electrical change triggers a wave of excitation along a muscle fiber.

Contractility

Capacity of muscle to shorten when stimulated.

Extensibility

Ability of muscle to be stretched between contractions.

Elasticity

Tendency of muscle to return to its original length after stretching.

Endomysium

Thin connective tissue wrapping each individual muscle fiber.

Perimysium

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

Epimysium

Fibrous sheath that encloses an entire muscle.

Fascia

Sheet of connective tissue that separates neighboring muscles or groups.

Fascicle

A bundle of skeletal muscle fibers wrapped together by perimysium.

Tendon

Dense regular connective tissue connecting muscle to bone.

Aponeurosis

Broad, flat tendon such as the palmar aponeurosis.

Origin

Bony attachment at the stationary end of a skeletal muscle.

Insertion

Bony attachment to the movable end of a skeletal muscle.

Muscle belly

Thick, middle region of a muscle between origin and insertion.

Innervation

Identity of the nerve that stimulates a muscle to contract.

Somatic motor neuron

Nerve cell whose axon innervates skeletal muscle fibers.

Motor unit

One motor neuron and all the muscle fibers it innervates.

Neuromuscular junction (NMJ)

Specialized synapse where a motor neuron communicates with a muscle fiber.

Synaptic knob (terminal)

Swollen axon ending at the NMJ that contains neurotransmitter vesicles.

Synaptic vesicle

Membrane sac in the synaptic knob storing acetylcholine.

Acetylcholine (ACh)

Neurotransmitter released at NMJs to excite skeletal muscle fibers.

Acetylcholinesterase

Enzyme that degrades ACh in the synaptic cleft, ending stimulation.

Resting membrane potential (RMP)

Electrical charge difference (≈ –90 mV) across the sarcolemma of a resting fiber.

Action potential

Rapid, self-propagating change in membrane voltage that travels along a muscle fiber.

Sarcolemma

Plasma membrane of a muscle fiber.

Sarcoplasm

Cytoplasm of a muscle fiber containing myofibrils, glycogen, and myoglobin.

Myofibril

Long protein cord inside a muscle fiber composed of repeating sarcomeres.

Myofilament

Protein filament (thick or thin) that slides to produce contraction.

Thick filament

Myosin-based filament found in the A band of a sarcomere.

Myosin

Motor protein whose heads bind actin and hydrolyze ATP for force.

Thin filament

Actin-based filament with associated troponin and tropomyosin.

Actin

Globular protein that forms the backbone of thin filaments.

Tropomyosin

Regulatory protein that blocks myosin-binding sites on actin at rest.

Troponin

Calcium-binding protein that moves tropomyosin to expose actin sites.

Sarcomere

Functional contractile unit of a myofibril from one Z disc to the next.

A band

Dark region of a striation where thick and thin filaments overlap.

I band

Light region containing only thin filaments, bisected by a Z disc.

H band (zone)

Central region of the A band containing thick filaments only.

Z disc

Protein plate that anchors thin and elastic filaments; marks sarcomere boundaries.

T tubule

Invagination of the sarcolemma that conducts action potentials into the fiber interior.

Sarcoplasmic reticulum (SR)

Smooth ER of muscle storing and releasing Ca²⁺ for contraction.

Triad

T-tubule flanked by two terminal cisternae of SR.

Ryanodine receptor

Calcium-release channel in the SR opened during excitation-contraction coupling.

Dihydropyridine (L-type) channel

Voltage sensor in the T-tubule that mechanically opens RyR channels.

Excitation–contraction coupling

Link between action potential on sarcolemma and sliding of filaments.

Sliding filament mechanism

Process in which myosin heads pull thin filaments toward the M line, shortening sarcomeres.

Power stroke

Flexing of a myosin head that pulls the thin filament in contraction.

Recovery stroke

Return of myosin head to cocked position after ATP binding and detachment.

ATPase

Enzyme activity of the myosin head that hydrolyzes ATP for energy.

Creatine phosphate (phosphocreatine)

High-energy storage molecule that donates phosphate to ADP for quick ATP resynthesis.

Glycogen

Stored polysaccharide of glucose within muscle fibers for energy.

Myoglobin

Red pigment that stores oxygen inside muscle fibers.

Isometric contraction

Muscle develops tension without changing length; no movement occurs.

Isotonic contraction

Muscle changes length while tension remains constant; produces movement.

Concentric contraction

Isotonic action in which muscle shortens while generating force.

Eccentric contraction

Isotonic action in which muscle lengthens while maintaining tension.

Slow-twitch fiber (Type I)

Red, fatigue-resistant muscle fiber adapted for endurance and posture.

Fast-twitch fiber (Type IIb)

White, quick-fatiguing fiber adapted for rapid, powerful contractions.

Hypertrophy

Increase in muscle fiber size due to resistance training.

Hyperplasia

Increase in muscle fiber number (limited contribution to muscle growth).

Muscle tone

Partial, involuntary contraction of resting skeletal muscles maintained by the CNS.

Length–tension relationship

Principle that muscle force depends on initial sarcomere length before stimulation.

Tetanus (state)

Sustained muscle contraction caused by rapid repetitive stimulation or toxin.

Flaccid paralysis

Loss of muscle tone and inability to contract, often from neuromuscular blockade.

Curare

Plant toxin that competes with ACh for its receptor, causing flaccid paralysis.

Botulism

Paralytic illness from Clostridium botulinum toxin that blocks ACh release.

Myasthenia gravis

Autoimmune disease where antibodies destroy ACh receptors leading to weakness.

Duchenne muscular dystrophy

Sex-linked disorder caused by lack of dystrophin leading to progressive muscle degeneration.

Intercalated disc

Specialized junction connecting cardiac muscle cells, containing gap and mechanical junctions.

Autorhythmicity

Ability of cardiac (and some smooth) muscle cells to generate spontaneous depolarizations.

Calmodulin

Calcium-binding protein that initiates smooth muscle contraction by activating MLCK.

Myosin light chain kinase (MLCK)

Enzyme that phosphorylates myosin heads in smooth muscle enabling cross-bridge cycling.

Sphincter

Ring of smooth or skeletal muscle that regulates passage of materials through openings.

Glycemic control

Role of skeletal muscle in absorbing and storing glucose to regulate blood sugar.

Heat production

Generation of up to 85 % of body heat via skeletal muscle metabolism.

Antigravity muscle

Skeletal muscle that prevents the body from falling, maintaining posture.

Connectin (Titin)

Elastic protein anchoring thick filaments to Z disc, contributing to recoil.

Myoblast

Embryonic stem cell that fuses to form a multinucleate skeletal muscle fiber.

Voltage-gated sodium channel

Membrane protein that opens during depolarization, propagating action potentials.

End-plate potential

Local depolarization at the motor end plate produced by ACh binding.

Depolarization

Reduction or reversal of membrane potential, making the interior less negative.

Repolarization

Return of membrane potential to a negative value after depolarization.

Piloerector muscle

Smooth muscle in skin that raises hairs when cold or frightened.

Autonomic nervous system

Motor division controlling involuntary effectors such as cardiac and smooth muscle.

Troponin–tropomyosin complex

Regulatory system on thin filaments controlling exposure of myosin-binding sites.

Ca²⁺ pump (SERCA)

Active transport protein returning calcium to the SR during relaxation.

Latch state

Sustained tension in smooth muscle with minimal ATP consumption.

Sarcoplasmic calcium

Ca²⁺ released into cytosol that triggers muscle contraction.

Toxin

Chemical that can disrupt normal neuromuscular function, causing tetanus or paralysis.