Chapter 12: Microscopic Anatomy and Organization of Skeletal Muscle

Actin

thin filaments

Titin

Elastic filaments

Myosin

thick filament

Muscle fibers

muscle cells

Myofibers

long organelles inside muscle cell

Myofilaments

actin and myosin

Sarcomeres

units composed of actin and myosin that contract inside the muscle fiber

Transverse tubule (T tubule)

tubular infoldings of the sarcolemma

Sarcoplasmic Reticulum (SR)

smooth ER that forms a network around each myofibril

Triads

formed by t tubules that run between the paired teminal cisternae of SR; organelles come into closest contact here; encircle each sarcomere

Endomysium

Connective tissue surrounding a muscle fiber

Perimysium

Connective tissue surrounding a fascicle

Fascicle

bundle of muscle fibers

Epimysium

covers the entire skeletal muscle

Tendons

Connect muscle to bone

Aponeurosis

A broad, flat tendon

neuromuscular junction

Synapse between motor neuron and muscle fiber.

Motor unit

a motor neuron and all the muscle cells it stimulates

synaptic cleft

gap between adjacent neurons

Sarcolemma

muscle cell membrane