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The Neuromuscular Junction

The Neuromuscular Junction. Chapter 10 Anatomy and Physiology Mr. Knowles Liberty Senior High School. Neuromuscular Junction (NMJ). Communication b/w the nervous system & skeletal muscle fiber. Soma. Soma. Neuromuscular Junction (NMJ). As an axon enters a muscle, it

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The Neuromuscular Junction

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  1. The Neuromuscular Junction Chapter 10 Anatomy and Physiology Mr. Knowles Liberty Senior High School

  2. Neuromuscular Junction(NMJ) Communication b/w the nervous system & skeletal muscle fiber.

  3. Soma

  4. Soma

  5. Neuromuscular Junction(NMJ) As an axon enters a muscle, it branches into a number of synaptic terminals, each of which forms a NMJ with a single muscle Fiber.

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

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

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

  9. When a neuron stimulates a muscle fiber, Heeeeere’s what happens . . .

  10. 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.

  11. 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.

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

  13. 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.

  14. 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

  15. Normal

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

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

  18. Effects of a Nerve Agent

  19. Atropine Antidote

  20. What is myasthenia gravis?

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