GSU NEUR 3000 - NEUR 3000 - Chapter 5 (53 pages)

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NEUR 3000 - Chapter 5



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NEUR 3000 - Chapter 5

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Pages:
53
School:
Georgia State University
Course:
Neur 3000 - Hon Principles of Neuroscience

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SYNAPTIC TRANSMISSION NEUR 3000 Dr Joseph J Normandin SYNAPTIC TRANSMISSION The process by which information is transferred between neurons At some synapses electrical signals pass through physical connections between neurons Electrical synapses At other synapses electrical signals are converted into a chemical signal Chemical synapse In both systems we have A presynaptic neuron before the synapse A postsynaptic neuron after the synapse TYPES OF SYNAPSES Electrical synapses The pre and postsynaptic cells are physically connected by gap junctions The cells are only 3 nm apart Gap junctions are formed by the protein connexin Six connexin forming a ring comprise a connexon Two connexons one from each cells form the gap junction channel The channel is large enough for ions and small molecules to flow through TYPES OF SYNAPSES TYPES OF SYNAPSES TYPES OF SYNAPSES Electrical synapses Information flow is bi direction as electric current can flow both ways Very fast conduction A presynaptic action potential will produce a postsynaptic potential in the postsynaptic neuron In the mammalian brain this potential is small at about 1 mV Summation of postsynaptic potentials from many cells can result in an action potential Synaptic integration An action potential in the postsynaptic neuron will result in a PSP in the previously presynaptic neuron Present in systems requiring synchrony TYPES OF SYNAPSES TYPES OF SYNAPSES Chemical synapses Pre and postsynaptic cells are not continuous with one another The space in between is referred to as the synaptic cleft 20 50 nm wide A fibrous matrix between the two cells keeps the synapse anchored TYPES OF SYNAPSES Chemical synapses The presynaptic element is usually an axon Contains synaptic vesicles with neurotransmitters Large neuropeptide containing vesicles are called dense core vesicles A pyramid shaped active zone on the intracellular side of terminals is where vesicles bind The postsynaptic element is usually a dendritic spine The



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