Principles of Human Anatomy - Chapter 10: Muscular Tissue

Comprehensive practice flashcards covering vocabulary terms, functional properties, anatomical layers, and physiological mechanisms of muscular tissue from Chapter 10.

Contractility

The ability of muscular tissue to contract forcefully when stimulated.

Extensibility

The ability of muscular tissue to be stretched without being damaged.

Skeletal Muscle Fiber

A single cylindrical cell with a hundred or more nuclei arranged in parallel fashion, which can reach lengths of up to $30\,\text{cm}$ ($12\,\text{in.}$).

Myosin

A motor protein in all types of muscle tissue that forms thick filaments, features protruding heads and tails, and resides within the A band of the sarcomere.

Sarcoplasmic Reticulum (Structure A)

A fluid-filled system of membranous sacs encircling each myofibril that stores and releases $\text{Ca}^{2+}$ to trigger skeletal muscle contraction.

Transverse (T) Tubule

A tube-shaped invagination of the sarcolemma that opens to the outside of the cell and propagates muscle action potentials deep into the muscle fiber.

Triad

A structural complex in skeletal muscle fibers formed by the close association of one transverse (T) tubule and two terminal cisterns of the sarcoplasmic reticulum.

Sliding Filament Mechanism

The process of muscle contraction during which myosin cross-bridges pull thin filaments inward so their ends meet or overlap in the center of the sarcomere.

Neuromuscular Junction (NMJ) Transmission

The sequence in which a nerve impulse triggers ACh release into the synaptic cleft, ACh binds to motor end plate receptors, and a muscle action potential is initiated.

Muscular Hypertrophy

An increase in overall muscle size caused by an increased diameter and volume of individual skeletal muscle fibers rather than an increase in cell number.

Muscular Atrophy

A reduction in muscle size resulting from a decrease in the diameter and size of skeletal muscle fibers.

Fast Glycolytic (Type IIb) Fibers

Muscle fibers containing the least amount of myoglobin, specialized for generating explosive power during short bursts of activity, which fatigue most rapidly.

Slow Oxidative (Type I) Fibers

Fatigue-resistant, oxygen-rich muscle fibers adapted for endurance-type activities and the continuous maintenance of body posture.

Fast Oxidative-Glycolytic Fibers

Intermediate skeletal muscle fibers that are largest in diameter and capable of both aerobic cellular respiration and anaerobic glycolysis.

Cardiac Muscle Tissue

Involuntary, striated muscle tissue composed of branching cells with centrally located nuclei, abundant mitochondria, and intercalated discs.

Smooth Muscle Tissue

Involuntary, nonstriated muscle tissue lacking transverse tubules and organized sarcomeres, found in the walls of viscera and blood vessels.

Visceral (Single-Unit) Smooth Muscle

Smooth muscle tissue organized into continuous sheets whose cells connect by gap junctions to contract simultaneously as a single unit.

Multiunit Smooth Muscle

Smooth muscle tissue consisting of distinct individual fibers that operate independently of one another due to an absence of gap junction coupling.

Motor End Plate

The specialized region of the sarcolemma opposite the synaptic end bulb that contains transmembrane receptors specific for acetylcholine.

A Band

The darker middle region of a sarcomere that spans the entire length of the thick filaments and contains actin, myosin, titin, troponin, and tropomyosin.

I Band (Structure A)

The lighter, less dense zone of a myofibril containing only thin filaments, which narrows and shortens during muscle contraction.

Tropomyosin

A regulatory protein in thin filaments that covers the myosin-binding sites on actin monomers when a muscle fiber is at rest.

Troponin

A regulatory protein on the thin filament that binds $\text{Ca}^{2+}$, initiating a shape shift that moves tropomyosin away from actin active sites.

Somatic Motor Neuron

A nerve cell that delivers electrical impulses directly to a skeletal muscle fiber to stimulate its contraction.

Endomysium

A layer of loose connective tissue, primarily composed of reticular fibers, that wraps around and insulates each individual muscle fiber.

Perimysium

A sheath of dense irregular connective tissue that groups individual skeletal muscle fibers into bundles called fascicles.

Epimysium

The outermost layer of dense irregular connective tissue encircling an entire skeletal muscle that binds all fascicles together.

Motor Unit

A single somatic motor neuron and all the individual skeletal muscle fibers that it innervates.

Myofibrils

Longitudinal contractile elements extending throughout the sarcoplasm of a muscle fiber, composed of regular arrays of thick and thin myofilaments.

Satellite Cells

Myoblasts that persist in adult skeletal muscle tissue and retain a limited regenerative capacity to repair damaged muscle fibers.

Synaptic Cleft

A narrow extracellular gap separating the axon terminal of a motor neuron from the sarcolemma of the muscle cell at the neuromuscular junction.

Body Movement Production

A primary function of muscular tissue resulting from skeletal muscles pulling on bones, enabling activities such as walking and raising limbs.

Body Position Stabilization

A muscle function where sustained contractions of postural muscles stabilize skeletal joints and maintain continuous posture.

Substance Storage and Movement

A muscle tissue function wherein smooth muscle sphincters regulate the internal storage and passage of substances through hollow organs.

Heat Production (Thermogenesis)

A physiological muscle function where heat is released as a natural by-product of skeletal muscle contraction to maintain core temperature.

Nebulin

A giant structural protein that wraps along the full length of each thin filament, anchoring it securely to the Z disc.

Autorhythmicity

The intrinsic ability of certain cardiac and smooth muscle cells to repeatedly generate spontaneous, rhythmic action potentials.

Fascia

Broad sheets of dense irregular connective tissue that wrap around and separate functional groups of skeletal muscles.

Acetylcholine (ACh)

The specific neurotransmitter released from motor neuron axon terminals at the neuromuscular junction to trigger muscle excitation.

Muscle Tone

A sustained, baseline level of tension in a muscle resulting from weak, alternating, involuntary contractions of its motor units.

Intercalated Discs

Irregular transverse cell junctions in cardiac muscle tissue that integrate desmosomes for structural connection and gap junctions for electrical coupling.

Synaptic Vesicle

A small membrane-enclosed sphere inside the synaptic end bulb containing stored molecules of neurotransmitter.

Tendon

A thick, dense regular connective tissue band extending from the connective tissue coverings of a muscle that attaches directly to the periosteum of bone.

Somites

Paired, block-like mesodermal embryonic segments that give rise to the skeletal musculature of the thoracic wall, abdominal wall, and limbs.

Mesoderm

The primary embryonic germ layer from which nearly all muscular tissues in the human body originate.

Acetylcholinesterase (AChE)

An enzyme residing in the synaptic cleft that rapidly hydrolyzes acetylcholine to terminate muscle action potential generation.

Concentric Isotonic Contraction

A muscle contraction where the muscle shortens while pulling on an attached bone to produce movement and decrease the joint angle.

Isometric Contraction

A muscle contraction in which mechanical tension is developed without altering the overall length of the muscle or moving a load.

Muscular Dystrophy

A group of genetic, muscle-wasting diseases marked by progressive degeneration of skeletal muscle fibers caused by mutations in the dystrophin gene.

Clostridium tetani

A bacterium introduced through puncture wounds that releases a toxin causing severe, unremitting muscle rigidity and potentially fatal respiratory failure.