7 - BIO 317: Lecture 7 Prof. William Collins Ofce: 534 Life...

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1 Prof. William Collins OfFce: 534 Life Sciences Building OfFce Hours: Mondays, 4:00 – 5:00 PM or by appointment Recommended Reading: Matthews - chapter 5 BIO 317: Lecture 7 Knee-Jerk Reflex NMJ is Model synapse
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2 Chemical Synaptic Transmission animation Types of Chemical Synaptic Transmission Fast Chemical Synaptic Transmission – Rapid, localized release of neurotransmitter – Rapid initiation and termination of neurotransmitter action (milliseconds) – Mediated by ligand-gated ion channels (ionotropic) Slow Chemical Synaptic Transmission – Transmitter release may localized or diffuse – Slower onset of neurotransmitter action (seconds) – Duration of action much longer (seconds minutes longer) • May last longer than neurotransmitter – Mediated by ligand-activated G-protein receptor
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3 Neuromuscular Junction (NMJ) • Neurotransmitter is Acetylcholine (ACh) • When ACh binds to receptor, channels open -> depolarization called, “end plate potential” (EPP) • A the NMJ, each EPP is usually very large and produces an AP in the muscle cell and contraction “one-for-one” synapse Summary of Presynaptic Events AP arrives in synaptic terminal Produces depolarization of synaptic terminal Voltage-dependent Ca ++ channels open Ca ++ enters synaptic terminal Ca ++ binds to calcium sensor molecules associated with synaptic vesicles Synaptic vesicles fuse with synaptic membrane Contents of synaptic vesicles ( neurotransmitter ) released into ECF directly across from target cell ( synaptic cleft ) -> local release
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4 Voltage-Gated Ca ++ Channels in Presynaptic Terminal • Depolarization opens Ca ++ channels high-voltage activated (HVA) fast, inactivating P/Q-type (Ca v 2.1) & N-type (Ca v 2.2) • Ca ++ enters from ECF [Ca ++ ] o 1 mM
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7 - BIO 317: Lecture 7 Prof. William Collins Ofce: 534 Life...

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