2 neuronal signals 1 - receptor potentials and sensory transduction - lecture slides

2 neuronal signals 1 - receptor potentials and sensory transduction - lecture slides

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Unformatted text preview: ignaling Within & Between Nerve Cells The Basis of Neuronal Signals & Neuronal Signals 1: Receptor Potentials & Sensory Transduction Neurophysiology University of Colorado at Boulder Department of Integrative Physiology Steps to Learning Goal Ion channels & why neurons need them Cell membranes Ohms Law Net driving forces Quantifying the contributions of ions Maintaining ionic gradients Gated ion channels Investigating properties of ion channels Receptors Potentials & Sensory Transduction Recommended Reading From Kandel et al. (2000) Principles of Neuroscience Chapter 6: Ion Channels, pp.103-123 Chapter 7: Membrane Potential, pp.125- 134, 138-139 Chapter 21: Coding of Sensory Information, pp. 414-416 Chapter 31: Sensory Transduction in the Ear, pp. 616-619 Nature of Electrical Signals (1) Electrical signals (local, graded potentials & action potentials) in the nervous system are generated by the selective movement of ions across the nerve cell membrane. Sensory neuron Ion Channels (2) Ionic movements are possible because of ion channels , which act as conductors : objects through which charge can flow. ion channels - integral membrane proteins that span cell membranes & form pores that ions can move through conductance ( g, ): capacity of an object to transmit a current (how easy it is for charged particles to move); measured in siemens ( S ). resistance ( R ; how difficult it is for charged particles to move): reciprocal of conductance (R=1/g); measured in ohms ( ); resistors act to hinder flow of charged particles. 1 o structure 2 o structure 3 o structure 4 o structure Basic Ion Channel Properties (3) conduct ions rapidly 10 8 ions/s mediate rapid changes in charge distribution across the nerve cell membrane (makes fast neuronal signaling possible) action potential = 500 V/s change across membrane recognize & select specific ions (specificity) Na + , K + , Cl , Ca ++ most allow only 1 ion species, some allow 2 or more some types are open all the time ( leakage = passive = resting ion channels) other types open & close ( gate ) in response to specific electrical, chemical & or mechanical signals Neuron cell membrane (4) Ion channels are necessary because the neuronal plasma membrane is a lipid bilayer. hydrophobic hydrophilic dipolar Because phospholipid bilayer is so thin, it is possible for ions on one side to interact electrostatically with ions on the other side producing a separation of charge across the cell membrane right at the membrane. Thus, the lipid bilayer acts like a capacitor (stores charge). Ion 6-8nm cytosol ECF Neuron cell membrane (5) Separation of charges across cell membrane produces a potential difference reported in units of volts (or mV) known as the membrane potential ( V m , V rest )....
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2 neuronal signals 1 - receptor potentials and sensory transduction - lecture slides

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