Study Guide Exam II

Study Guide Exam II - 1 Be able to identify the following...

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1. Be able to identify the following parts of a skeletal muscle diagram: a. Sarcomere – The structural subunit of a myofibril in a striated muscle; equal to the distance between two successive Z lines. b. Actin Filament – A structural protein of muscle that, along with myosin, is responsible for muscle contraction. c. Troponin – A protein found in the thin filaments of the sarcomeres of skeletal muscle. A subunit of troponin binds to Ca 2+ , and as a result causes tropomyosin to change position in the thin filament. d. Tropomysin – A filamentous protein that attaches to actin in the thin filaments. Together with another protein called troponin, it acts to inhibit and regulate the attachment of myosin cross bridges to actin. e. Myosin Filament – The protein that forms the A bands of striated muscle cells. Together with the protein actin, myosin provides the basis for muscle contraction. f. Sarcoplasmic Reticulum – The smooth or agranualar endoplasmic reticulum of striated muscle cells. It surrounds each myofibril and serves to store Ca 2+ when the muscle is at rest. g. T-Tubule – The terminal cisternae of the sarcoplasmic reticulum are separated only by a very narrow gap. These are narrow membranous “tunnels” formed from and continuous with the sarcolemma (muscle plasma membrane). h. A-Band – The dark bands are A-Bands. Thick filament, length of myosin. i. I-Band – The light bands are I-Bands. Just actin. j. Z-Line – At high magnification in an electron microscope, thin dark lines can be seen in the middle of the I bands. These are called Z lines. k. Cross Bridges – Sliding of the filaments is produced by the action of numerous cross bridges. Happens when muscle fiber contracts. 2. Be able to provide a brief description of the sequence of events in the excitation and contraction mechanism of skeletal muscle. The myosin head tilts, pulling the actin filament (power stroke). The myosin head realeases ADP and P i . ATP binds to myosin ADP + P i . Myosin head is in high-energy conformation. Crossbridge cycling continues as long as the AP continues and Ca
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Study Guide Exam II - 1 Be able to identify the following...

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