Exam _3 study guide - Exam #3 Study Guide Chapter 12...

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Exam #3 Study Guide Chapter 12 – Muscles The Structure of skeletal muscles Epimysium : (“above the muscle”) sheath of fibrous c.t. proteins w/in tendons extending around the muscle (“circumference” around the fasciculus) Fasciculus : columns / subdivisions of the muscle Perymysium : (“around the muscle”) sheath of fibrous c.t. surrounding / between the fasciculus Muscle fibers / myofibers : striated, multi-nucleated muscle cells Sarcolemma : muscle cell membrane Endomysium : thin c.t. layer covering the sarcolemma (between myofibers – inside the fasciculus) Motor Units Motor unit : each somatic neuron, together w/ all of the muscle fibers that it innervates Neuromuscular junction : junction where nerve synapses w/ the muscle (at motor end plate) Motor end plate : the specialized region of the sarcolemma of the muscle fiber at the neuromuscular junction Page 1 of 12
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Exam #3 Study Guide Recruitment : the successive stimulation of more & larger motor units in order to produce increasing strengths of muscle contraction Sliding Filament Theory of Contraction 1. A myofiber, together with all its myofibrils, shortens by movement of the insertion toward the origin of the muscle 2. Shortening of the myofibrils is caused by shortening of the sarcomeres – the distance between Z discs / lines is reduced. 3. Shortening of the sarcomeres is accomplished by sliding of the myofilaments – the length of each filament remains the same during contraction. 4. Sliding of the filaments is produced by asynchronous power strokes of myosin cross bridges, which pull the thin filaments (actin) over the thick filaments (myosin). 5. The A bands remain the same length during contraction, but are pulled toward the origin of the muscle. 6. Adjacent A bands are pulled closer together as the I bands between them shorten. 7. The H bands shorten during contraction as the thin filaments on the sides of the sarcomeres are pulled toward the middle. Myofibrils : (fibrils = little fibers) subunits of the myofibers / muscle fibers Filaments : small structures w/in myofibrils; bands of protein fiber that slide across each other to cause muscle movement (contraction) A-band – thick filaments: myosin (give the band its dark appearance) I-band – thin filaments: actin Z-disc : thin dark lines in the middle of the I band; “end” of a sarcomere Sarcomere : basic contractile structure of the muscle; from one Z disc to the next Page 2 of 12
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Exam #3 Study Guide Terminal cisternae : part of the sarcoplasmic reticulum that stores Ca + T-tubule : (transverse tubule) hole continuous w/ sarcolemma that conducts AP deep into the center of the muscle cell Sarcoplasmic reticulum : organelle on the inside of the muscle cell that stores Ca + Sarcoplasm : cytoplasm of a muscle cell (mostly H 2 O) Excitation-Contraction Coupling AP generated by a somatic motor neuron arrives at the motor end plate Acetylcholine (ACh – a neurotransmitter) is exocytosed into the myoneural synapse (causes the
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This note was uploaded on 09/24/2009 for the course PHYS 104 taught by Professor Pratt during the Spring '09 term at University of Indianapolis.

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Exam _3 study guide - Exam #3 Study Guide Chapter 12...

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