phys3a - Chapter 3 Synapses and Drugs: The Concept of the...

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Unformatted text preview: Chapter 3 Synapses and Drugs: The Concept of the Synapse Lecture 3 2 Properties of Synapses Sherrington: B data reflex arc synaptic delay summation inhibition Postsynaptic Potentials: excitatory ( EPSP )/ inhibitory ( IPSP ) dendrites/spines, soma slow or local or graded potentials can be either + or - EPSP IPSP Prob of a.p. Prob of a.p. Lecture 3 3 Properties of Synapses (cont) Temporal Summation Overlap of EPSPs & IPSPs in time Spatial Summation Summation of potentials (EPSPs & IPSPs) across cell body & dendrites Lecture 3 4 Temporal & Spatial Summation Lecture 3 5 Neural Information Processing Spontaneous Firing Rate Modified by temporal & spatial summation Pattern & Rate of Firing = Information Neuronal Networks Lecture 3 6 Chemical Events at the Synapse Synthesis of Transmitters Depends upon neuronal type: biogenic amines amino acids peptides Precursors: diet blood cell Location peptides synthesized only in cell body other transmitters can be synthesized in cell body & terminal, eg catecholamines (epinephrine, norepinephrine, dopamine) Lecture 3 7 Chemical Events at the Synapse Transport of Transmitters . .. . . . le s s tim e to re p le n is h , e g A C h more time to replenish eg enkephalin Speed variable 1mm/day to 100 mm/day hours to days Lecture 3 8 Chemical Events at the Synapse Release & Diffusion of Transmitters Action potential causes Ca ++ influx release of transmitters Transmitters released in quanta stored inside or outside of synaptic vesicles spew transmitter into synaptic cleft Diffusion across synaptic cleft & attaches to receptor (~.5 to 2 msecs) Lecture 3 9 Synapse Lecture 3 10 Lecture 3 11 Chemical Events at the Synape Postsynaptic Receptor Activation Lock-and-key analogy Neurotransmitter (NT) key opens receptor lock ion channels open The same NT may effect different receptors differently Ionotropic Effects rapid but short-lived (~10-20 msecs) Lecture 3 12 Chemical Events at the Synapse Postsynaptic Receptor Activation (cont) Ionotropic effects (cont) 4 major types of NT-dependent ion channels: 1. Na + (depolarizing) 2. K + (hyperpolarizing) 3. 3....
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phys3a - Chapter 3 Synapses and Drugs: The Concept of the...

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