Lecture 4-NMJ

Lecture 4-NMJ - Neuromuscular Junction (NMJ) A special...

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Fig. 8-4 B&B Neuromuscular Junction (NMJ) A special synapse between neuron and skeletal muscle
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axon axon terminals •RMP •AP •Propagation of AP •EPP CNS MN Neuromuscular junction (NMJ) Skeletal muscle cells SPINAL CORD
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B&L Fig. 12-7 B
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NEUROMUSCULAR JUNCTION (NMJ) 1. The NMJ is the junction between the axon terminal of an alpha motor neuron and a skeletal muscle cell. 2. There is only one NMJ for each skeletal muscle cell. 3. The NMJ is located near the middle of the muscle cell. 4. The function of the NMJ is to transmit information from the neuron to the muscle cell. 5. It does this by releasing acetylcholine (Ach), an excitatory neurotransmitter. 6. Ach produces an end-plate potential (EPP) in the skeletal muscle cell that leads to contraction.
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Fig. 8-4 B&B Synaptic vesicles in the active zones are aligned with Ach receptors on the end plate to maximize response.
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Fig. 8-2 B&B Fig. 8-4 B&B Fig. 7-12B B&B
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Nicotinic Type Acetylcholine Receptor A ligand-gated channel 
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Na + K + AchR is a Ach-gated non-selective cationic channel When two molecules of Ach binds on AchR, the channel opens and let through K+, Na+ and Ca2+, But not anion such as Cl-. gCa2+ through AchR is very small, most of the conductance is gK+ and gNa+. When AchR opens, it tries to bring Vm to 0 mV, which greatly depolarizes the end plate.
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Concentration gradient Electrical gradient SKELETAL MUSCLE CELL Na + o = 140mM K + o = 4 mM K + i = 170 mM Na + i = 12 mM mV 0 RMP = - 90 + +++ --- + + + + RMP = - 90 mV E Na = + 65mV E K = - 100 mV
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Time (msec) Memb. pot. (mv) 0 - 100 +100 +
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This note was uploaded on 02/23/2011 for the course PGY 451 taught by Professor Baizer during the Spring '09 term at SUNY Buffalo.

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Lecture 4-NMJ - Neuromuscular Junction (NMJ) A special...

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