The neuromuscular junction disorders including myasthenia gravis
The Neuromuscular Junction
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Transcript of The Neuromuscular Junction
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The Neuromuscular Junction
Chapter 10
Anatomy and Physiology
Mr. Knowles
Liberty Senior High School
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Neuromuscular Junction
(NMJ)Communication b/w the nervoussystem & skeletal muscle fiber.
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Soma
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Soma
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Neuromuscular Junction
(NMJ)As an axon enters a muscle, it branches into a number of synaptic terminalssynaptic terminals, each of whichforms a NMJ with a single muscleFiber.
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Synaptic Terminal
•Contains Molecules of Acetylcholine (ACh).Acetylcholine (ACh).
•AChACh is a neurotransmitter, chemical released by neurons to change the membrane properties of other cells.
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Synaptic Cleft•A narrow spacenarrow space that
separates the synaptic terminal of the neuron from the sarcolemma surface.
•Contains Acetylcholinesterase (AChE)(AChE) which breaks down AchAch.
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Motor End Plate•The surface of the sarcolemma that contains membrane receptors that bind ACh.ACh.
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When a neuron stimulates a muscle fiber, Heeeeere’s what happens . . .
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The arrival of an action potential
•Sudden change in the transmembrane potential along the axon.
•This stimulates the release of AChACh at the synaptic terminal.
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The release of ACh•Vesicles that contain ACh,ACh, in the synaptic terminal, fuse with the membrane of the neuron & are released by exocytosis into the synaptic cleft.
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ACh binding at the motor end plate
•AChACh molecules diffuse across the synaptic cleft & bind to AChACh receptorsreceptors on the motor end plate’s surface.
•When AChACh binding occurs, sodium ions (Na(Na++)) now can rush into the sarcoplasm.
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Appearance of an action potential in the
sarcolemma• The NaNa++ results in an action potential in the sarcolemma.
• The action potential sweeps across the entire membrane surface & travels down each of the T tubulesT tubules which triggers the release of CaCa2+2+ at the terminal cisternae.terminal cisternae.
• While this is occurring, AChE AChE removes the ACh.ACh.
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Return to the initial state
• Even before the action potential has spread across the entire membrane, the AChACh has been broken down by AChEAChE.
• This sequence of events can now be repeated, should another AP arrive at the synaptic terminal
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Normal
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Show me the action! Potential, that is!
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What happens at the neuromuscular junction
when exposed to botulinum toxin?
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Effects of a Nerve Agent
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Atropine Antidote
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What is myasthenia gravis?