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Synaptic plasticity

Synaptic plasticity. Definition. Alteration of synapse response to input. Synaptic plasticity. Relevance Adapting to environment Neurodevelopment Learning & memory. Examples. PTP versus fatigue LTP vs LTD. LTP. NMDA hypothesis. LTP. Presynaptic modification AA → G-protein

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Synaptic plasticity

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  1. Synaptic plasticity

  2. Definition • Alteration of synapse response to input

  3. Synaptic plasticity • Relevance • Adapting to environment • Neurodevelopment • Learning & memory

  4. Examples • PTP versus fatigue • LTP vs LTD

  5. LTP • NMDA hypothesis

  6. LTP • Presynaptic modification • AA → G-protein • NO → GC • Postsynaptic modification • CaM Kinase II • cAMP, cGMP-dependent • Tyrosine kinase (fyn) • Synaptic structure • widening of neck of spine Glutamate release TF Activation Receptor Upregulation

  7. Spike timing • Variant of Hebbian learning • Donald Hebb (1949) • NMDA Dependent • Reversible • strengthening is function of EPSP-spike delay

  8. Integration • Convergence of much information • Input: up to 10,000 synapses + sensory input • Output: one axon • Time dependent • Long term state of cell • State of receptors + membrane in short term • Each synapse different • distance from soma, other synapses • neurotransmitter combination • receptor types, number and sensitivity

  9. Neuronal mechanisms of integration • Dendritic tree • diameter • voltage gated ion channels • EPSP and IPSP • temporal + spatial summation • decay with distance and time • shunting inhibition • Axon hillock • threshold behaviour

  10. Repetitive firing Adaptation Accommodation Delay firing Subthreshold oscillation LTP / LTD (De-)sensitisation Down- / Upregulation Synaptic growth Calcium mediated integratory effects Fast (ionic) Slow (second messenger)

  11. Membrane properties • RM (per unit length) = s pd • RI (per unit length) = 4 r / pd2 • CM (per unit length) = cpd

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