SC BIOL 460 - Muscle Cells (3 pages)

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Muscle Cells

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Muscle Cells


Excitation and tension relationship of muscle cells and the motor unit

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University Of South Carolina-Columbia
Biol 460 - General Physiology
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BIOL 460 1st Edition Lecture 17 Outline of Last Lecture I Skeletal Muscle a Myofibers i A bands ii I bands b Mechanism of muscle contraction c Cross bridge cycling Outline of Current Lecture I Excitation of Muscle Cells II Length Tension Relationship III Motor Unit Current Lecture Excitation of muscle cells 1 Caused by somatic motor neurons 2 Synapse neuromuscular junction 3 Has large terminal bouton 4 1 neuromuscular junction per muscle fiber 5 sarcolemma of muscle fiber at neuromuscular junction is called motor end plate 6 trigger for contraction calcium which bonds to troponin 7 need 10 6 M of Ca2 for contraction 8 relaxation occurs when there isn t a high enough Ca2 concentration 9 Ca2 comes from sarcoplasmic reticulum 10 Relaxation established by calcium pumps 11 SR wraps around every myofibril in each cell These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 12 Most of Ca2 found in terminal cisternae 13 T tubule transverse runs from one side of muscle fiber to the other a Formed from invagination of sarcolemma b Go around myofibrils c Have lumen that is continuous with extracellular environment 14 Receptors on motor end plate are cholinergic nicotinic a Open ion channels and generate EPSP b EPSP on motor end plate end plate potential c Edges of motor end are analogous to axon hillock d Opens K Na VGC if at threshold e Causes action potential conducted across sarcolemma f VGC extend into PM lining t tubules g Propagates AP deep into the muscle fiber 15 Getting Ca2 into sarcoplasm a Minor way Ca2 VGC in sarcolemma especially in t tubules b Opens as a result of a conformation change in Ca2 VGC c Most Ca2 comes from SR i Exits via release channels 2 types ii Mechanically coupled Ca2 release channels 1 Electromechanical release mechanism 2 Mechanically coupled with Ca2 VGC of sarcolemma 3 Conformation change of Ca2 VGC is mechanically coupled to RC the physical

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