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BME 402 Homework 5 Due 12:30 pm, 3/7/06 Synapses: Overview Be able to compare and contrast electrical synapses (gap junctions) and chemical synapses, in terms of where in the nervous system they occur, their approximate dimensions, their physical components (know the basic vocabulary), their transmission delays, their directionality, and their functional uses. In particular, be able to explain what advantages accrue to chemical synapses that justify their much greater complexity. Be able to name at least 8 neurotransmitters, and be able to say a couple of interesting/informative things about each (such as where they are found, whether excitatory or inhibitory or both, whether they are involved in direct or 2ndmessenger gated transmission or both, what diseases are associated with their imbalances, what drugs or blockers act on their receptors, etc.). Know what is meant by “reversal potential”, and what this corresponds to in an electric circuit representation, and what the reversal potentials typically are for excitatory and inhibitory synapses (and what ions are involved). Neuromuscular Junction Be able to draw the basic structure of the NMJ including the single axon (and know where the parent neuron lives), its multiple release sites on the endplate, as well as a cross sectional view of the pre- and post-synaptic terminals. Know some approximate numbers: how many vesicles are typically released, how many channels are typically activated, how large is the typical EPSP in the muscle fiber. Know what neurotransmitter is used, and what ions carry the synaptic current. Be able to draw what the synaptic response looks like under both current and voltage clamp including the approximate time course. Know several things that can go wrong with the NMJ, including the names of at least one toxin that blocks the ACh receptor, another that interferes with pre-synaptic release, and a drug that acts on acetylcholinesterase. Be able to desribe how the symptoms of at least one disease arise from dysfunction at the NMJ. Synaptic Transmission in the CNS Be able to compare and contrast synaptic transmission at the NMJ vs. in the CNS. Be able to state the most likely physical locations of excitatory vs. inhibitory synapses on a typical CNS neuron (i.e. whether on the cell body, dendritic shafts, spines, pre-synaptic terminals), and know what Gray’s type I and II synapses correspond to. Know what the terms AMPA and NMDA refer to, and be able to explain how NMDA channels are different from AMPA channels in terms of their opening/closing time courses, their I-V curves when open, and the ions they conduct. Know the names of selective blockers for AMPA and NMDA channels (CNQX and APV, respectively). Be able to state semi-quantitatively how two simultaneously active synaptic responses summate within the same voltage compartment of a cell, whether (1) two AMPA synapses, (2) two NMDA synapses, (3) an AMPA and a hyperpolarizing inhibitory synapse, or (4) an AMPA and a
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