Skeletal Muscle and Muscle Fibers

Module 9: Muscle Tissue

Skeletal Muscle

Voluntary striated muscle usually attached to bones

Fascia

A fibrous membrane, covering, supporting and separating muscles

Muscle Fibers (cells)

Fusion of multiple myoblasts during development

Satellite cells

Lie between the endomysium and the muscle fibers

Sarcolemma

plasma (cell) membrane of muscle fiber

Transverse (T) tubules

Tubular inner foldings of the sarcolemma

Glycogen

Stored energy

Myoglobin

Binding oxygen

Sarcoplasm

Cytoplasm of a muscle (cell) fiber

Sarcoplasmic reticulum

Smooth ER

Terminal cisternae

Stores calcium

Triad

T Tubule and 2 terminal cisterna

Thick filaments

Made of several hundred myosin molecules (myosin is a motor protein)

Thin filaments

Composed of three different protein types (actin, troponin and tropomyosin)

Elastic filaments

Made of a huge, springy protein called titin

Myosin: Thick Filaments

Made of 200 to 500 myosin molecules

Actin: Thin Filaments

Two intertwined protein strands with an active site

Tropomyosin

long protein chain that covers active site on actin

Troponin

one small calcium-binding protein on each tropomyosin molecule

Contractile proteins

myosin and actin

Regulatory proteins

tropomyosin and troponin