lecture5-11

lecture5-11 - Lecture 5 SYNAPTIC TRANSMISSION synapses make...

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Unformatted text preview: Lecture 5 SYNAPTIC TRANSMISSION synapses make the connections between nerve cells. one nerve cell can have thousand of synaptic inputs (convergence). The inputs each can cause a local graded potential (hyper- or depolarization). The integration of these inputs will determine if the post-synaptic cell will have an action potential that one nerve cells can contact many other cells at synapses (divergence of output). real synaptic input is MUCH more complex. One cell can have thousands of inputs. Synapses (green) of hippocampal neurons cultured in vitro. There are two principle types of synapses: chemical and electrical the simplest, and les abundant type is the ELECTRCAL SYNAPSE In an electrical synapse, the cytoplasms of the pre- and post-synaptic cells are joined by gap junctions. This allows the direct flow of current from on cell to the next. Synaptic transmission is faster than in chemical Electrical synapses are often found in neural systems that require the fastest possible response, such as defensive reflexes. does not allow for much integration in post-synaptic cell. Used for simple behaviors. Not appropriate for synaptic modification associated with complex behaviors like learning. electrical chemical electrical The Chemical Synapse Synapses allow for the biological computations that underlie both unconscious behaviors and conscious thought. our brains our thought to have 10 14 to 5 ! 10 14 (100-500 trillion) synapses. arrival of the action potential to the axonal terminus results in release of chemical signal into the synaptic gap (or cleft). the neurotransmitter binds to a receptor on the post-synaptic cells and may cause either depolarization or hyperpolarization. the time required for the release, diffusion, and binding of the neurotransmitter causes a brief delay in synaptic transmission. synaptic vesicle (neurotransmitter) postsynaptic density synaptic cleft Events in pre-synaptic cell (chemical):...
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lecture5-11 - Lecture 5 SYNAPTIC TRANSMISSION synapses make...

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