Muscles and Muscle Tissue

Comprehensive vocabulary flashcards covering skeletal, cardiac, and smooth muscle tissues, myofilament anatomy, contractile mechanics, myograms, and associated muscular disorders.

Skeletal Muscle

A type of muscle tissue characterized as striated and voluntary, responsible for producing body movement.

Cardiac Muscle

A type of muscle tissue characterized as striated and involuntary, composed of squarish, Y-shaped fibers connected by intercalated discs.

Smooth Muscle

A type of muscle tissue characterized as nonstriated and involuntary, which lacks sarcomere organization.

Epimysium

An extension of deep fascia that covers the whole muscle.

Perimysium

An extension of deep fascia that covers muscle fiber bundles called fascicles.

Endomysium

An extension of deep fascia that covers individual muscle fibers.

Sarcolemma

The plasma membrane of a muscle cell.

Transverse Tubules

Tiny invaginations of the sarcolemma that penetrate into the muscle fiber.

Sarcoplasm

The cytoplasm of a muscle cell.

Sarcoplasmic Reticulum

A specialized organelle in muscle fibers dedicated to the storage of intracellular calcium ions.

Myoglobin

An oxygen-binding molecule found within muscle cells.

Myofiber

A skeletal muscle cell.

Myofibril

Small threads that fill each myofiber and run its entire length.

Myofilaments

Smaller threads that make up each myofibril and are arranged into segments called sarcomeres.

Thick Filament

A myofilament composed of the contractile protein myosin.

Thin Filament

A myofilament composed of the contractile protein actin and the regulatory proteins troponin and tropomyosin.

Elastic Filament

A myofilament composed of the structural protein titin.

Sarcomere Structure

The segmental unit of a myofibril bounded by Z discs, containing overlapping thick and thin filaments, light I bands, dark A bands, an H zone, and an M line.

Motor Unit

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

Twitch Contraction

A brief contraction of a muscle fiber occurring in response to a single action potential.

Myogram of a Twitch Contraction

A graphical representation of muscle tension over time following a single stimulus, showing the latent period, period of contraction, and period of relaxation.

Stimulation Frequency Responses

Patterns of muscle tension that vary according to stimulus rate, progressing from a single twitch to wave summation, unfused (incomplete) tetanus, and fused (complete) tetanus.

Recruitment

The activation of different motor units to adjust the force of contraction depending on need.

Intercalated Discs

Specialized connections that join cardiac muscle fibers to one another to form two major functional networks: the atria and the ventricles.

Single-Unit Smooth Muscle

A smooth muscle arrangement in which fibers are connected by gap junctions and contract together as a single unit.

Multiunit Smooth Muscle

A smooth muscle arrangement in which individual fibers contract independently.

Dense Bodies

Structures in smooth muscle cells attached to the sarcolemma that anchor intermediate filaments to transmit tension during contraction.

Smooth Muscle Cell Contraction

The shortening mechanism in smooth muscle cells where sliding filaments transmit tension to intermediate filament bundles that pull on membrane-attached dense bodies.

Caveoli

Plasma membrane invaginations in smooth muscle cells that are present in place of transverse tubules.

Calmodulin

A regulatory protein in smooth muscle that binds intracellular calcium ions to activate myosin light chain kinase.

Myosin Light Chain Kinase

An enzyme activated by calcium-bound calmodulin that transfers energy from ATP to myosin heads to initiate contraction in smooth muscle.

Myasthenia Gravis

An autoimmune skeletal muscle disorder caused by antibodies directed against acetylcholine receptors in the motor end plate.