2/1/16 February 1, 20 16 Aspects of electrical activity in a - PDF document

2/1/16 February ¡1, ¡20 16 Aspects of electrical activity in a neuron explained by understanding some very basic electrical concepts Introduction ¡to ¡Neuron ¡Models, ¡Course ¡Software 1. Voltage attenuation from a source of current injection Keep in mind: Class participation important 2. Distortion of voltage with distance and time Expect assignments on time 3. Greater AP conduction speed of large axons Review Course policies on Blackboard 4. Greater AP conduction speed of myelinated axons Review “Expectations” 5. Repolarization of APs at nodes of Ranvier without IK V 6. Synaptic Integration- Why we can think! What are the biological representations of Biological representations of the relevant electrical parameters the relevant electrical parameters of a neuronal membrane? of a neuronal membrane. Current across membrane with hyperpolarizations I m = I Rm + I Cm 1

2/1/16 Steady-state Vm determined by Rm. Steady-state Vm determined by Rm. How do resistance add in series?- cells connected by electrical junctions How do we categorize ion channels? How do they add in parallel?? – ion channels in a neuronal membrane What other important properties can differentiate channels that have the same activators? How do we categorize ion channels? What open or closes them? What is their selectivity? 2

2/1/16 Other important properties that differentiate channels. Once a channel is open, what Law does it obey? Inactivation kinetics Activation kinetics Only a few equations needed in Neurobiology : Opening probability Conductance The separation of unlike charge results in a tendency for an electrical current flow. The extent of current flow depends on the conductance (or its reciprocol, resistance) of the medium separating the charges. All can be changed by neuromodulators What law is this? ¡ ¡ Ohm’s Law Ohm’s Law V=IR V=IR ! ! The!separation!of!unlike!charge!results!in!a!tendency!for!an! The!separation!of!unlike!charge!results!in!a!tendency!for!an! electrical!current!flow.!!The!extent!of!current!flow!depends!on! electrical!current!flow.!!The!extent!of!current!flow!depends!on! the!conductance!(or!its!reciprocol,!resistance)!of!the!medium! the!conductance!(or!its!reciprocol,!resistance)!of!the!medium! separating!the!charges.! separating!the!charges.! ! ! ! ! ! Since!R=!1!/!G! ! ! ! Since!R=!1!/!G! ! ! ! ! I!=!V!/!R! ! V=!I!/!G! ! ! ! ! I!=!V!/!R! ! V=!I!/!G! ! ! ! ! R!=!V!/I! ! I!=!V!x!G! ! ! ! ! ! ! R!=!V!/I! ! I!=!V!x!G! ! ! ! ! ! ! ! ! ! ! G!=!I!/!V ! ! ! ! ! ! ! ! G!=!I!/!V How ¡does ¡a ¡separation ¡of ¡specific types ¡of ¡charges ¡occur ¡across ¡a ¡cell ¡membrane? How ¡does ¡a ¡separation ¡of ¡specific types ¡of ¡charges ¡occur ¡across ¡a ¡cell ¡membrane? Membrane ¡barrier, ¡ion ¡pumps ¡channel ¡permeability 3

2/1/16 Membrane Cm Channels follow Ohm’s law Membrane Cm Cm on voltage change across the membrane Out What is a capacitor? C= Q/V What makes a capacitor stronger or weaker? How does capacitance affect a voltage change? In How does capacitance add in series and in parallel? How is capacitance relevant to Neurobiology? 4

2/1/16 This week First Lab: Model Neuron: Membrane resistance, Oscilloscope primer, Time constant, A/D software tutorial- Introduction to Lab Chart 5