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Types of Muscle cont.
Smooth Walls of visceral
organs Force fluids through
internal channels Not voluntary Not striated
Gross Anatomy of a Skeletal Muscle
Epimysium Outermost layer Connective tissue surrounding the entire
muscle tapers at end to form tendon
Endomysium Thin connective tissue surrounding each
muscle fiber (cell) Smallest unit of muscle visible without a
microscope
Skeletal Muscle
Muscles always contract actively Can extend only passively Ability to move a bone part in opposite
directions requires that muscles be attached to the skeleton
Tire easily Bundle of long fibers running the length of the
muscle Each fiber is a single cell with many nuclei &
consists of bundles of smaller myofibrils arranged longitudinally
Muscle Fiber
Single muscle cell Cylindrical in structure Surrounded by membrane capable of excitation &
impulse propagation Contains muscle fiber bundles called myofibrils
Sarcolemma
Delicate sheath (cell membrane)
Made up of lipid molecules
Transport nutrients & synthesizes proteins
Sodium/potassium pump
Maintain shape of muscle cell
Sarcoplasm
Aqueous substance – cytoplasm
Surrounds myofibrils House the
mitochondria Houses blood
vessels, glycogen & nerve endings
Myofibrils
Fibers functional unit Threadlike structure within muscle fiber Contains sarcomeres at intervals Made up of 2 protein fibers – microfilaments
Sarcoplasmic Reticulum
Specialized endoplasmic reticulumFunction is to store calcium and release
it on demand when a muscle fiber is stimulated to contract
Initiates muscle contraction at the sarcomere
Sarcomere
Segment of myofibril Composed of 2
contractile proteins Actin Myosin
Sarcomeres are separated by Z lines
Sarcomere
Has a dark band – A band
The A band has light zone called the H band (this disappears when contracted)
Center of the H band is the M line
Myofilaments
Protein fibers Composed of 2
filaments Actin – thin Myosin - thick
Divided into bands which alternate light and dark
Thick filaments
A bands are dark areas Dark areas represent
thick filaments 2 thick filament dark
areas are connected by the M line
Consist of myosin & ATPase
Enzyme splits ATP to generate the power of muscle contractions