Muscle Fiber Structure

• Muscle->Fascicle->Fiber->Myofibril->Filaments• Fascia – A layer of connective tissue that

separates muscles and holds muscles in place

• Muscle->Fascicle->Fiber->Myofibril->Filaments• Fascicle – A bundle of muscle cells• Epimysium – A layer of connective tissue that

closely surrounds a skeletal muscle• Perimysium – Another layer of connective tissue

that extends inward and separates the fascicles

• Muscle->Fascicle->Fiber->Myofibril->Filaments• Fiber – A muscle cell, very long and thin• Sarcolemma – Cell membrane of a muscle cell• Sarcoplasm – Cytoplasm of a muscle cell• Sarcoplasmic Reticulum – Endoplasmic Reticulum

of a muscle cell• Transverse (T) Tubule – Membranous channels

that extend into the sarcoplasm from invaginations in the sarcolemma, assist with action potential movement

• Muscle->Fascicle->Fiber->Myofibril->Filaments• Myofibril – A bundle of thick and thin filaments

(proteins)• Myosin – A protein that makes up thick filaments• Actin – A protein that makes up thin filaments• Troponin – Attached to actin, made of 3 protein

subunits• Tropomyosin – Attached to actin, longtitudinal

Thin Filaments

Thick Filament

• Muscle->Fascicle->Fiber->Myofibril->Filaments• Sarcomere – Alternating patterns of myosin and

actin, creates striations in cardiac and skeletal muscle

• I bands – Light bands, made of thin filaments (actin), anchored by Z lines

• A bands – Dark bands, made of thick filaments (myosin), anchored by M lines, thick and thin filaments overlap in this area

• H Zone – Area where only thick filaments exist