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Neuromuscular Junction
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR 2 6 3
ADP Pi Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process. Removal of Ca2+ by active transport into the SR after the action potential ends. SR Tropomyosin blockage restored, blocking myosin binding sites on actin; contraction ends and muscle fiber relaxes. Ca2+ 1 2 3 4 5 6 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle ACh
Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh
Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. 1 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR Ca2+ 2
Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. SR Ca2+ 1 2 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR 2 3 Ca2+
Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. SR Ca2+ 1 2 3 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR 2 3 Ca2+
Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process. SR Ca2+ 1 2 3 4 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR 2 3 Ca2+
Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process. Removal of Ca2+ by active transport into the SR after the action potential ends. SR Ca2+ 1 2 3 4 5 Figure 9.10
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Figure 9.10 Synaptic cleft vesicle 1 ACh SR tubules (cut) SR 2 6 3
ADP Pi Net entry of Na+ Initiates an action potential which is propagated along the sarcolemma and down the T tubules. T tubule Sarcolemma SR tubules (cut) Synaptic cleft vesicle Axon terminal ACh Neurotransmitter released diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma. Action potential in T tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR into cytosol. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin; actin active sites exposed. Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process. Removal of Ca2+ by active transport into the SR after the action potential ends. SR Tropomyosin blockage restored, blocking myosin binding sites on actin; contraction ends and muscle fiber relaxes. Ca2+ 1 2 3 4 5 6 Figure 9.10
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