What specific event initiates the contraction Calcium release from the

What specific event initiates the contraction calcium

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What specific event initiates the contraction? Calcium release from the sarcoplasmic reticulum initiates the contraction. A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected? A series of proteins that control calcium release. What is name given to the regularly spaced infoldings of the sarcolemma? transverse or T tubules Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? Calcium ions. What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? A myosin head bound to actin What structure is the functional unit of contraction in a skeletal muscle fiber? The sarcomere Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? Calcium ions are stored in the sarcoplasmic reticulum. After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? ATP binds to the myosin head. How does the myosin head obtain the energy required for activation? The energy comes from the hydrolysis of ATP. What specific event triggers the uncovering of the myosin binding site on actin? Calcium ions bind to troponin and change its shape. of 190 380
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When does cross bridge cycling end? Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. What area of the thick filament binds to actin once actin's binding sites are exposed? myosin cross-bridge (head) Contraction Cycle Calcium ions arrive within the zone of overlap Calcium ions bind to troponin. Active sites on actin are exposed Myosin heads bind to actin active sites The myosin head pivots (power stroke). ADP and P are released ATP binds to the myosin head, breaking the link. The free myosin head "recooks". ADP and P are released Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur? Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate. The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment?
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  • Spring '10
  • TONE
  • muscle tension, Skeletal Muscle Tissue, anatomy and physiology I

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