Muscle Tissue & Microscopic Anatomy – Lecture Review

Vocabulary flashcards covering key muscle tissue types, microscopic structures, and sarcomere components discussed in the lecture.

Skeletal Muscle Tissue

Voluntary, striated muscle composed of long fibers that run the entire length of the muscle.

Cardiac Muscle Tissue

Involuntary, striated muscle found only in the heart; fibers are branched and connected by intercalated discs.

Smooth Muscle Tissue

Involuntary, non-striated muscle composed of spindle-shaped cells found in walls of hollow organs and blood vessels.

Striation

Alternating light and dark bands produced by the arrangement of actin and myosin in skeletal and cardiac muscle.

Muscle Fiber

A single muscle cell; in skeletal muscle it is as long as the entire muscle and surrounded by endomysium.

Myofibril

Cylindrical sub-unit of a muscle fiber; composed of repeating sarcomeres and responsible for contraction.

Fascicle

A bundle of muscle fibers surrounded by perimysium within a whole muscle.

Sarcomere

The smallest contractile unit of a myofibril, extending from one Z disc to the next.

Actin

Protein that forms thin filaments within the sarcomere; interacts with myosin to produce contraction.

Myosin

Protein that forms thick filaments within the sarcomere; its heads bind to actin during contraction.

Endomysium

Connective tissue sheath surrounding each individual muscle fiber.

Perimysium

Connective tissue sheath surrounding each fascicle (bundle of fibers).

Epimysium

Connective tissue sheath surrounding an entire muscle; continuous with tendons.

Sarcolemma

The plasma membrane of a muscle fiber.

Sarcoplasmic Reticulum

Modified endoplasmic reticulum in muscle fibers that stores and releases calcium ions.

Transverse (T) Tubule

Invagination of the sarcolemma that carries the action potential deep into the muscle fiber.

Z Disc

Protein line that defines the boundaries of a sarcomere and anchors thin filaments.

I Band

Light band of a sarcomere containing only thin filaments; spans two adjacent sarcomeres.

A Band

Dark band of a sarcomere containing the entire length of thick filaments and overlapping thin filaments.

H Zone

Central region of the A band containing only thick filaments (no overlap).

M Line

Protein line in the center of the H zone that stabilizes thick filaments.

Zone of Overlap

Area within the A band where thick and thin filaments overlap, allowing cross-bridge formation.

Thin Filament

Filament composed mainly of actin along with troponin and tropomyosin.

Thick Filament

Filament composed of myosin molecules with protruding heads that form cross-bridges.

Intercalated Disc

Specialized junction connecting cardiac muscle cells; contains gap junctions and desmosomes.

Mitochondrion (in muscle)

Organelle providing ATP for contraction; abundant in muscle fibers.

Tendon

Dense regular connective tissue formed by merging epimysium, perimysium, and endomysium; connects muscle to bone.

Periosteum

Dense connective tissue covering bone; continuous with tendons for muscle attachment.

Spindle-Shaped Cell

Characteristic shape of smooth muscle cells—wide in the middle, tapering at both ends.

Myofibril Reticulum Network

Combined arrangement of sarcoplasmic reticulum and T tubules that surrounds each myofibril.