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The Neuromuscular Junction

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The Neuromuscular Junction

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    1. The Neuromuscular Junction Anatomy and Physiology Liberty Senior High School

    2. Neuromuscular Junction (NMJ)

    7. Neuromuscular Junction (NMJ)

    9. Synaptic Terminal Contains Molecules of Acetylcholine (ACh) ACh is a neurotransmitter, chemical released by neurons to change the membrane properties of other cells

    10. Synaptic Cleft A narrow space that separates the synaptic terminal of the neuron from the sarcolemma surface Contains Acetylcholinesterase (AChE) which breaks down ACh

    13. Motor End Plate The surface of the sarcolemma that contains membrane receptors that bind ACh

    16. The arrival of an action potential Sudden change in the transmembrane potential along the axon This stimulates the release of ACh at the synaptic terminal

    18. The release of ACh Vesicles that contain ACh, in the synaptic terminal, fuse with the membrane of the neuron & are released by exocytosis into the synaptic cleft

    19. ACh binding at the motor end plate ACh molecules diffuse across the synaptic cleft & bind to ACh receptors on the motor end plate’s surface When ACh binding occurs, sodium ions (Na+) now can rush into the sarcoplasm

    20. Appearance of an action potential in the sarcolemma The Na+ results in an action potential in the sarcolemma The action potential sweeps across the entire membrane surface & travels down each of the T tubules which triggers the release of Ca2+ at the terminal cisternae While this is occurring, AChE removes the ACh

    21. Return to the initial state Even before the action potential has spread across the entire membrane, the ACh has been broken down by AChE. This sequence of events can now be repeated, should another AP arrive at the synaptic terminal

    23. Show me the action! Potential, that is!

    26. What happens at the neuromuscular junction when exposed to botulinum toxin?

    29. Sarcoplasmic Reticulum Pumps Ca+2 out of the sarcoplasm and stores it. The resting cell has very little Ca+2 in the sarcoplasm. 1000X more Ca+2 in the SR than in the sarcoplasm. The SR is made up of terminal cisternae that lie on above the junction of thin and thick filaments in the sarcomeres.

    30. Sarcoplasmic Reticulum As an Action Potential passes down the T-tubule, it stimulates the terminal cisternae to release enough Ca+2 to saturate all the troponin in the sarcomere.

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