Muscle Tissue & Physiology – Vocabulary Review

Vocabulary flashcards summarizing major structures, properties, processes, and clinical terms related to skeletal, cardiac, and smooth muscle tissue from the lecture notes.

Actin

Primary protein of thin filaments; binds with myosin during muscle contraction.

Myosin

Motor protein of thick filaments; its heads attach to actin to form cross-bridges.

Perimysium

Connective tissue layer surrounding fascicles (bundles of muscle fibers).

Skeletal Muscle

Voluntary, striated muscle tissue that moves the body by pulling on bones.

Cardiac Muscle

Involuntary, striated, branched muscle of the heart; contains intercalated discs.

Smooth Muscle

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

my/o- (Prefix)

Medical prefix meaning muscle (e.g., myosatellite, myopathy).

sarc/o- (Prefix)

Medical prefix meaning flesh or muscle tissue (e.g., sarcomere, sarcoma).

Intercalated Discs

Specialized junctions connecting cardiac muscle cells, enabling synchronized contraction.

Striated Muscle

Muscle displaying repeating light and dark bands (skeletal and cardiac).

Non-Striated Muscle

Muscle lacking visible banding pattern (smooth muscle).

Myofilament

Protein filament (actin or myosin) responsible for contraction within muscle fibers.

Troponin

Regulatory protein that binds calcium and moves tropomyosin to expose actin sites.

Tropomyosin

Protein that blocks actin’s active sites until troponin–calcium interaction occurs.

Excitability

Ability of muscle cells to respond to a stimulus and generate action potentials.

Contractility

Capacity of muscle fibers to shorten forcibly when stimulated.

Extensibility

Capability of muscle tissue to stretch without damage.

Elasticity

Ability of muscles to recoil to original length after stretching.

Cross-Bridge

Physical link formed when myosin heads bind to actin during contraction.

Epimysium

Outer connective tissue sheath surrounding an entire skeletal muscle.

Endomysium

Delicate connective tissue surrounding individual muscle fibers.

Myoblast

Embryonic muscle stem cell that fuses to form skeletal muscle fibers.

Myosatellite Cell

Adult stem cell aiding muscle growth and repair through protein synthesis.

Sarcolemma

Plasma membrane of a muscle fiber; initiates action potentials.

Transverse (T) Tubule

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

Terminal Cisternae

Enlarged regions of SR storing calcium; part of the triad.

Sarcoplasmic Reticulum (SR)

Specialized smooth ER that stores and releases calcium for contraction.

Sarcoplasm

Cytoplasm of a muscle fiber containing myofibrils and organelles.

Tendon

Cordlike connective tissue attaching muscle to bone.

Aponeurosis

Sheet-like tendon connecting muscle to bone or other muscles, distributing force.

Sprain

Injury involving overstretching or tearing of a tendon or ligament.

Sarcoma

Cancer arising from muscle, bone, or connective tissue (e.g., myosarcoma in muscle).

Sarcomere

Smallest functional contractile unit of a muscle fiber between two Z-lines.

A Band

Dark region of a sarcomere containing thick filaments (myosin).

I Band

Light region of a sarcomere containing thin filaments (actin) only.

Resting Membrane Potential

Baseline electrical charge (≈ -70 mV) across a muscle cell’s membrane.

Triad

Structure of two terminal cisternae plus one T tubule coordinating calcium release.

Titin

Elastic protein anchoring thick filaments and providing recoil after stretch.

Neuromuscular Junction (NMJ)

Synapse between a motor neuron and a skeletal muscle fiber.

Acetylcholine (ACh)

Neurotransmitter released at NMJs to trigger muscle action potentials.

Depolarization

Process where membrane potential becomes less negative (more positive).

Repolarization

Return of membrane potential toward resting value after depolarization.

Hyperpolarization

Temporary overshoot where membrane potential becomes more negative than resting level.

Rigor Mortis

Post-mortem stiffening of muscles starting 2–6 h after death due to ATP depletion.

Physiological Tetanus

State of maximal sustained muscle tension from high-frequency stimulation.

Thermogenesis

Heat production by muscles during ATP-dependent contractions.

Isotonic Contraction

Contraction where muscle changes length while tension remains constant.

Isometric Contraction

Contraction generating tension without changing muscle length.

Creatine Phosphate

High-energy molecule providing 10–15 s of rapid ATP resynthesis.

Anaerobic Respiration

ATP production without oxygen, leading to lactic acid buildup.

Aerobic Respiration

Oxygen-dependent ATP production within mitochondria; dominant in endurance activity.

Fast Fibers (Type II)

White, fast-twitch skeletal fibers adapted for quick, powerful movements; anaerobic.

Slow Fibers (Type I)

Red, slow-twitch fibers specialized for endurance; chiefly aerobic.

Intermediate Fibers (Type IIa)

Pink fast-oxidative fibers combining features of fast and slow fibers.

Muscle Hypertrophy

Increase in muscle fiber size from resistance training or protein synthesis.

Muscle Atrophy

Decrease in muscle mass from disuse, aging, or disease.

Cardiomyocyte

Cardiac muscle cell; striated, branched, uninucleate, forms heart tissue.

Automaticity

Ability of cardiac cells to generate spontaneous action potentials.

Pacemaker Cells

Specialized cardiomyocytes (SA node, AV node, etc.) that set heart rhythm.

SA Node

Sinoatrial node; primary pacemaker initiating each heartbeat.

Arrector Pili

Smooth muscle attached to hair follicles; contraction causes goosebumps.

Sliding Filament Theory

Model describing how actin and myosin slide past each other to shorten sarcomeres.

Thermal Homeostasis

Maintenance of body temperature aided by muscle-generated heat.