4 Influence of Passive Membrane Properties on Neural Signals - lecture slides

4 Influence of Passive Membrane Properties on Neural Signals - lecture slides

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Unformatted text preview: Signaling Within & Between Nerve Cells Influence of Passive Membrane Properties on Neuronal Signals Neurophysiology University of Colorado at Boulder Department of Integrative Physiology Steps to Learning Goals Electrical equivalent circuits Passive neuron properties & influence on current flow membrane resistance membrane capacitance axial resistance Influence of passive properties on neuronal signals spatial & temporal integration of synaptic & receptor potentials speed of propagation of action potentials (conduction velocity) Recommended Reading From Kandel et al. (2000) Principles of Neuroscience Chapter 7: Membrane Potential, pp. 134-138 (Electrical Equivalent Circuits) Chapter 8: Local Signaling- Passive Electrical Properties of the Neuron, pp. 140-149 Chapter 22: The Bodily Senses, p. 444-446 Also see Appendix A, for more information on electrical components. Electrical Signals (1) Neurons use electrical signals (local, graded potentials & action potentials) to transmit information in the nervous system. Electrical characteristics of cell membrane influence both local, graded potentials & action potentials. Sensory neuron Electrical Equivalent Circuits (2) Electrical characteristics of cell membrane, & thus functional properties of neurons, can be represented by electrical components & electrical equivalent circuits . Equivalent circuit model comprises: conductors or resistors batteries capacitor current generators Electrical Equivalent Circuit (3) These components are arranged in parallel or in series with one another. Components we are representing are all associated with the membrane (exist in the membrane, or across the membrane) & influence current flow across the membrane. extracellular side cytoplasmic side extracellular side cytoplasmic side membrane In series membrane In parallel Representation of Ion Channels (4) Ion channels can be represented as conductors ( resistors ) in series with batteries (E X ). For ex., all passive K + channels in nerve membrane can be lumped into single equivalent electrical structure: a battery (E K ) in series with a conductor (g K ). Direction of current flow is shown as emanating from positive terminal. I K Representation of Ion Channels (5) Each population of resting ion channel (Na + , K + , or Cl- ) can thus be represented by battery (E X ) in series with conductor (g x ). E K = -75mV E Na = +55mV E Cl = -80mV Current Generators (Na +-K + Pump) (6) Na +-K + pump keeps ionic batteries charged and can therefore be added to equivalent circuit in form of a current generator (actually two current generators)....
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4 Influence of Passive Membrane Properties on Neural Signals - lecture slides

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