Notes Skeletal Muscle Anatomy 1 Levels of Organization

Notes: Skeletal Muscle Anatomy

(1) Levels of Organization Macroscopic Microscopic • • • Muscle (whole organ) Fascicle (portion of muscle) Muscle Fiber (single muscle cell) Myofibril (muscle cell organelle) Sarcomere (portion of myofibril) Myofilament (part of sarcomere)

Fascicle Muscle (organ) Muscle Fiber (cell) Myofibril Muscle Fiber (with many nuclei) Sarcomere Thin Filament (actin) Thick Filament (myosin)

(2) Muscle • Organ of muscular system • Contains: – Muscle Cells – Connective Tissue – Blood Vessels & Nerves – Contractile Units • Covered By: – Epimysium (outer tissue-membrane)

(3) Fascicle • Portion of muscle-organ • One step down from whole muscle • Relationships: – Bunch of Fascicles = Muscle – Fascicle = Bunch of Muscle Fibers

(4) Muscle Fiber • Actual Muscle Cell • Contains: – Multiple nuclei – Striations – Complex organelles called myofibrils • Relationships: – Bunch of Muscle Fibers = Fascicle – Muscle Fiber = Bunch of Myofibrils & Nuclei

(5) Myofibril • Organelle in a muscle cell • Contains: – Contractile Units (Sarcomere) • Relationships: – Bunch of Myofibrils = Muscle Fiber – Myofibril = Bunch of Sarcomere

(6) Sarcomere • Portion of myofibril • Contains: – Contractile proteins – Thin filaments with actin – Thick filaments with myosin • Relationships: – Bunch of Sarcomeres = Myofibril – Sarcomere = Bunch of Myofilaments (Actin + Myosin)

(7) Myofilaments • Contractile portions of sarcomere • Types: – Thin filaments w/actin (type of protein) – Thick filaments w/myosin (type of protein) • Relationships: – Bunch of Myofilaments = Sarcomere – Myofilaments = DO THE CONTRACTIONS