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MSK Characteristics Lecture/slides Kine 1020 York University

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Kinesiology & Health Science
KINE 1020
Angelo Belcastro

MSK Characteristics Categories of Muscles Skeletal  Striated – aligned structures  Voluntary  Helps in locomotion  Posture  Heat production in cold stress  600 skeletal muscles Cardiac  Striated as well  Electrically coupled cells  If one is activated, the next one is also activated  involuntary Smooth Muscles  Non-striated  Involuntary  Line intestines, stomach Structure of Skeletal Muscle Muscle – many muscles in the body composed of many cells  Fascicle - bundle of muscle cells  Muscle cell - elongated structure unlike other cells  Myofibril - contractile unit, also the cause of striation in muscles, responsible for force, speed generated by muscle. Single muscle cell as ~2500 myofibril units Sarcomere  Located within myofibrils  Responsible for the action produced by a muscle  The different regions are categorized by the amount of protein found in the various regions of the sarcomere  A band: More protein, hence appears darker in the muscles. Composed of Actin  I band: few proteins, hence appears light  H band: Composed of myosin Sarcomere Proteins Actin  Composed of globular proteins  Associated with troponin; combine to create tropomyosin Myosin  Contain enzymatic activity ATPase Actin and Myosin Interaction Requirements  Energy in the form of ATP  For myosin to be able to de/attach to actin, needs ATP  Needs to transform chemical energy into mechanical  ATP is hydrolysed by MyosinATPase(head of myosin), which helps release the chemical energy in ATP  Calcium  Prepare actin filament to be ready for myosin  Binds to group of proteins called Troponins, found on the F actin  Binding causes movements that allows binding site on actin to be available for myosin  Causes Z line to move closer (shortening, contraction)  Alignment of proteins  Protein-protein interaction (mechano-transduction)  Alignment of sarcomeres, myofibrils and muscle cells Sarcoplasmic Reticulum  Site of storage for calcium  Membranous system  T-tubule interacts with the exterior of the cell, to regulate calcium levels in the cell  Nerve impulse (action potential), sends signal entering through T-tubule releasing calcium  After the movement, calcium is taken up again into the reticulum Protein-Prote
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