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Lecture 3

Lecture 3.docx

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Rutsuko Ito

Lecture 3synaptic integration and neuromodulation Lecture overviewsynaptic integration o temporal and spatial summation o factors that affect dendritic synaptic integrationpassive properties of dendrites active properties of dendritesback propagation of action potentialsinhibitory influencesbeyond neurotransmission o concept of bidirectional information flow o extrasynaptic neurotransmission o neuromodulation Synaptic integration in CNSunlike a muscle fibre that receives 1 excitatory input from 1 motor neuron the majority of central neurons receive inputs from hundreds of neurons which can be both excitatory and inhibitoryevery action potential in a motor neuron produces an action potential in the muscle fibre o an action potential in a central neuron is triggered only after a certain threshold of synaptic potential is reached after the integration of thousands of excitatory and inhibitory inputsTraditional view of synaptic integrationsynaptic integration results from simple algebraic summation near the soma with dendrites as mere conduits delivering synaptic potentials to the site of integration Dendritic treeprimary function of the dendritic tree is to collect and funnel information received at individual synapses to the soma and axon o ramon y cajaldendrites are principal sites for synaptic inputo spines on the dendrites are important in the consolidation of memoryTemporal and spatial summationtemporal o algebraic sum of EPSPs that arise close in timespatial o algebraic sum of EPSPs from different areas of inputProblemgiven the varying distance of synapses across the dendritic tree from the axon site of AP generationo how do synapses located at distant dendritic sites influence AP generationfour major factorspassive and active properties of dendritesaction potential backpropagationsynaptic placement and inhibitory influences Factors affecting dendritic synaptic integration passive properties of dendritesactive properties of dendrites action potential backpropagationsynaptic placement and inhibitory influences Passive properties of dendritescable theory o dendrites can be treated as spatially extended branched cables subject to the laws of cable theory information travels through dendrites at speeds and distances according to the specific properties of the dendrite itself cablemembrane resistanceo how leaky a membrane iso a hose with holes ion channels openingo high membrane resistancehigher length constantmembrane capacitanceo storage of charges that are equal and opposite on either side of the membraneo dependant on surface membrane areadiameter of dendrite internal axial resistance o internal resistanceobstacles inside the dendrites eg bumpshow wide or narrow it is
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