Chapter 4 - Synaptic Transmission

Chapter 4 - Synaptic Transmission - SY APTIC TRA SMISSIO &...

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(Chapter 4) . How do neurons talk to each other ? Sherrington, in 1906, suspected something special he called Synapse (Fig. 4.7) Working on reflexes, he noted: reflexes are slower there is temporal and spatial summation there is excitation of some muscles and inhibition of others The synapse : region where one axon terminal interacts with another neuron (Fig . 4.7) . Electrical synapses : gap junctions: Transmission from one neuron to the other is fast, and can be bidirectional. This type of synapsis is not plastic. Is found during some stages of development, and in some regions in adult specimens of some species. Most synapses in vertebrate brains are chemical. Recent studies show that gap junctions are found throughout the mammalian brain, associated with local neural inhibitory circuits. Chemical synapses : Transmission is mediated by chemical substances: neurotransmitters (Fig. 4.9; 4.10). A neurotransmitter is a chemical substance that transmits the neural signal from one neuron to another. Directed synapses: release of transmitters and postsynaptic receptors are close to each other (Fig. 4.7) release of neurotransmitters is at some distance from the receptors (Fig. 4.9) Otto Loewi demonstrated the chemical nature of synaptic transmission. Otto Loewi’s dream experiment (1920). He was later awarded the Nobel Prize. Structure of the synapse (Fig. 4.7)
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Presynapstic and postsynaptic membrane Synaptic cleft : space between presynaptic and postsynaptic elements (0.05 mm) Synaptic terminal contains synaptic vesicles which are full of neurotransmitters. Sequence of events at a chemical synapse -Neuron synthetizes neurotransmitters in cell body (e.g., peptide neurotransmitters). Small-molecule neurotransmitters can be synthetized at the axon terminal. -Transmitters are transported to the axon terminals by microtubules. Transmitters are stored in synaptic vesicles. -The arrival of an action potential at the synaptic button opens voltage-gated Ca ++ channels. -Ca++ ions flow into the synaptic button and vesicles attach to the presynaptic membrane. -Synaptic vesicles docked to the presynaptic membrane empty the neurotransmitters into the synaptic cleft: this process is called exocytosis. .
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This note was uploaded on 04/04/2012 for the course PSYCH 202 taught by Professor Kim during the Fall '06 term at University of Washington.

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Chapter 4 - Synaptic Transmission - SY APTIC TRA SMISSIO &...

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