Notes: Skeletal Muscle Anatomy
(1) Levels of Organization Muscle (whole organ) Fascicle (portion of muscle) Muscle Fiber (single muscle cell) Myofibril (muscle cell organelle) Sarcomere (portion of myofibril) Myofilament (part of sarcomere) Macroscopic Microscopic
Thick Filament (myosin) 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: Covered By: 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: Relationships: 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: Relationships: Contractile Units (Sarcomere) Relationships: Bunch of Myofibrils = Muscle Fiber Myofibril = Bunch of Sarcomere
(6) Sarcomere Portion of myofibril Contains: Relationships: 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