lecture 2Muscle Physiology part 1

A comprehensive set of vocabulary flashcards covering key structures, properties, and functions introduced in the muscle physiology lecture.

Skeletal Muscle Tissue

Voluntary, striated muscle attached to bones or skin; fibers are long, multinucleated cells responsible for body movements.

Cardiac Muscle Tissue

Involuntary, striated muscle of the heart composed of single-nucleated cells connected by intercalated discs to pump blood.

Smooth Muscle Tissue

Involuntary, non-striated, spindle-shaped muscle found in walls of viscera and blood vessels; moves substances via peristalsis.

Striations

Alternating light and dark bands in skeletal and cardiac muscle created by orderly arrangements of actin and myosin.

Intercalated Disc

Specialized junction containing gap junctions and desmosomes that electrically and mechanically link adjacent cardiac muscle cells.

Gap Junction

Protein channel connecting cytoplasm of two cells, allowing rapid ion flow and electrical communication (e.g., in cardiac muscle).

Spindle-shaped Cell

Cell that tapers at both ends and bulges in the middle; typical of smooth muscle fibers.

Peristalsis

Rhythmic, wave-like contractions of smooth muscle that propel contents through tubular organs (e.g., intestines).

Contractility

Property of muscle to shorten and generate pulling force.

Extensibility

Ability of muscle tissue to be stretched or lengthened without damage.

Elasticity

Ability of muscle to return to its original length and shape after contraction or extension.

Electrical Excitability

Capacity of muscle and nerve cells to respond to ionic imbalances (primarily Ca2+ and Na+) with action potentials.

Calcium Ion (Ca²⁺)

Divalent cation stored in the sarcoplasmic reticulum that triggers muscle contraction when released.

Sodium Ion (Na⁺)

Monovalent cation that moves through T-tubules and initiates action potentials in muscle fibers.

Actin

Thin filament protein that interacts with myosin to produce muscle contraction and forms part of striations.

Myosin

Thick filament motor protein whose heads bind actin and hydrolyze ATP to generate force during contraction.

Myoblast

Embryonic muscle precursor cell that differentiates and fuses to form muscle fibers.

Satellite Cell

Muscle stem cell located between sarcolemma and endomysium; fuses with fibers for growth and repair.

Muscle Fiber

Individual skeletal muscle cell; long, cylindrical, multinucleated, and packed with myofibrils.

Fascicle

Bundle of muscle fibers surrounded by perimysium within a whole muscle.

Endomysium

Delicate connective tissue sheath surrounding each individual muscle fiber.

Perimysium

Connective tissue layer encasing each fascicle of muscle fibers.

Epimysium

Dense connective tissue wrapping the entire muscle and continuous with tendons.

Tendon

Cord of dense regular connective tissue that anchors muscle to bone and is continuous with endo-, peri-, and epimysium.

Sharpie’s Fibers

Collagen fibers that embed tendons into periosteum, securing muscle attachments to bone.

Myofibril

Long, rod-like organelle inside muscle fibers composed of repeating sarcomeres; responsible for contraction.

Sarcolemma

Plasma membrane of a muscle fiber, invaginated to form T-tubules.

Sarcoplasmic Reticulum (SR)

Modified smooth ER in muscle fibers that stores and releases calcium ions for contraction.

Transverse (T) Tubule

Invagination of the sarcolemma that conducts action potentials deep into the muscle fiber.

Terminal Cistern

Enlarged end sacs of the sarcoplasmic reticulum that abut T-tubules and hold concentrated Ca²⁺.

Sarcomere

Smallest contractile unit of a myofibril, spanning from one Z-line to the next; contains overlapping actin and myosin.

Dystrophin

Cytoskeletal protein that anchors sarcomeres to the sarcolemma; mutations lead to muscular dystrophy.

Myo- / Sarco- Prefixes

Word roots indicating a relation to muscle (e.g., myofibril, sarcolemma).

Dense Regular Connective Tissue

Tissue with parallel collagen fibers providing great tensile strength; forms tendons and ligaments.

Mitochondrion

Organelle that produces ATP; abundant in muscle fibers to meet high energy demands.