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Lecture 3

Lecture 3 - c Normal Activation c.i By PSP’s at synapses...

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Lecture #3 (Action Potentials and Generator Potentials) I) Action Potentials (AP’s) a. Electrical Events b. Initialization of AP b.i. Input to neuron b.i.1. (PSP or electric stimulus) b.i.2. Small depolarization, change in membrane potential positive b.ii. Voltage-gated Stimulus Channel open b.iii. Open V.G. more Na+ influx more V.G. Na+ channels open. b.iii.1. Positive feedback b.iii.1.a. Very steep rising phase of AP b.iii.1.b. Peek less than or equal to E(Na)=62 mV b.iii.1.b.i. Any more positive, it will be pushed out charge repulsion b.iii.1.c. Termination b.iii.1.c.i. Time-dependent inactivation of V.G – Na Channels b.iii.2. Voltage-Gated K+ channels b.iii.2.a. Open when V up b.iii.2.b. Do not inactivate b.iii.2.c. Slower to open than are VG Na channels II) AP Features a. Threshold for firing AP’s a.i. If you push Vm> Threshold AP < Nothing b. All or none AP’s non-additive
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Unformatted text preview: c. Normal Activation c.i. By PSP’s at synapses c.ii. Electrode pass III) AP Propagation a. Active regeneration b. 48-10 IV)AP Refractory Period , Prevents backfiring a. Absolute Refractory Period (1 millisecond) VG Na channels are still inactivated b. Relative Refractory Period (2-3 millisecond) b.i. VG Na channels still open V) Saltatory Conduction a. Big axons wrapped with insulation myelin a.i. Separated by “nodes” b. AP moves by “jumping” from node to node faster VI)Generated Potentials (GP’s) a. In sensory neurons b. Transduce physical stimulus c. Crayfish c.i. Stretch receptor c.i.1. Increases stretch on muscle increases length, measure changes in V(GP) c.ii. Information about intensity encoded as frequency of AP’s not amplitude...
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Lecture 3 - c Normal Activation c.i By PSP’s at synapses...

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