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Applied Surgical Physiology Vivas - part 7

Ngoài kích thước của các sợi, sự khác biệt cấu trúc giữa các cơ xương và tim là gì? Một số khác biệt cấu trúc tế bào tim là đơn nhân, tế bào cơ xương multinuclear hạt nhân tế bào tim (myocyte) nằm ở trung tâm, nhưng ngoại biên đặt cho các tế bào xương, các sợi cơ tim là phân nhánh | M MUSCLE II - CARDIAC MUSCLE APPLIED SURGICAL PHYSIOLOGY VIVAS MUSCLE II - CARDIAC MUSCLE 1. Apart from the size of the fibres what are the structural differences between skeletal and cardiac muscle Some structural differences Cardiac cells are mononuclear skeletal muscle cells are multinuclear The cardiac cell myocyte nucleus is centrally located but peripherally located for skeletal cells Cardiac muscle fibres are branched unlike skeletal fibres Cardiac cells are connected to one another by intercalated disks. Gap junctions at these discs allow excitation to pass from one cell to another. Therefore cardiac myocytes contract as a syncitium The T tubule system which spreads the action potential is larger in cardiac muscle In cardiac muscle such T tubules are located at the Z line. In skeletal muscle it is located at the junction of the A and I bands 2. List some functional differences between skeletal and cardiac muscle. Skeletal muscle is voluntary Cardiac muscle contracts spontaneously myogenic In skeletal muscle Ca2 is released from the SR following spread of depolarisation through the T tubule network With cardiac muscle Ca2 -release from the SR is triggered by Ca2 that already been released by the SR and by Ca2 that has influxed through membrane voltage channels. This is called Ca2 -induced C f release T 102 M APPLIED SURGICAL PHYSIOLOGY VIVAS Mechanical summation and tetanus do not occur with cardiac muscle because of the longer duration of cardiac action potential In the case of skeletal muscle increases in force are generated by recruitment of motor units and mechanical summation see Skeletal muscle The force of cardiac muscle contraction is determined by the amount of intracellular Ca2 generated. For example through the action of hormones Note than in both types of muscle the initial fibre length at rest preload also determines the strength of contraction 3. Draw the action potential curve for the sino atrial SA node and a ventricular myocyte. What is the