Textbook Notes (368,311)
Canada (161,806)
Neuroscience (289)
NROB60H3 (151)
Chapter 5

Chapter 5 - Synaptic Transmission

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Janelle Leboutillier

CHAPTER 5SYNAPTIC TRANSMISSION y Synaptic transmission is the process of information transfer at a synapse The name synapse was given by the Charles Sherrington in 1897 y Electrical synapses are electrical current which flows from one neuron to the next most common in the mammalian brain Proven by Edwin Furshpan and David Potter y Chemical synapses are when chemical neurotransmitters transfer info from one neuron to another at the synapse Used by many CNS synapses and is the majority of synapses in the brain Proved by Otto Lowei in 1921Types of synapses y A synapse is the specialized junction where one part of a neuron contacts and communicates with another neuron or cell type y Gap junctions are where electrical synapses occur y Six connexins combine to form a channel called a connexon and two connexons one from each cell combine to form a gap junction channel y Diameter of a gap junction channel is about 12nm big enough for all major cellular ions and many small organic molecules to pass through y Electrical synapses are bidirectional y Cells connected by gap junctionselectrically coupled y Action potential in presynaptic neuron can produce instantaneously an action potential in the postsynaptic neuron y Postsynaptic potential PSP is when two neurons are electrically coupled an action potential in the presynaptic neuron causes a small amount of ionic current to flow across the gap junction channels into the other neurony When the second neuron generates an action potential it will in turn induce a PSP in the first neuronin the mammalian brain it is very small about 1 mV or less at its peaky Gap junctionsbetween neurons are particularly common during early embryonic stages y Gap junctions also interconnect many nonneural cells including glia epithelial cells smooth and cardiac muscle cells liver cells and some glandular cellsy Synaptic cleft is about 2050nm wide filled with a matrix of fibrous extracellular protein y Synaptic vesicles are small membrane enclosed spheres each about 50nm in diameterstores NT y Secretory granules are 100 nm in diameter and contain soluble protein that appears dark in electron microscopedense core vesicles y Membrane differentiations are dense accumulations or protein adjacent to and within the membranes on either side of the synaptic cleft y Active zones are where the pyramids and the membrane associated with them are releasing NTsPyramidsproteins from the presynaptic side that are jutting into the cytoplasm of the terminal along the intracellular face of the membraney Postsynaptic density is the protein thickly accumulated in and just under the postsynaptic membranecontains the NT receptors y Axodendritic is when the postsynaptic membrane is on a dendrite y Axosomatic is when the postsynaptic membrane is on the cell body y Axoaxonic is when the postsynaptic membrane is on another axon
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