Nervous SystemScopeAnimation1s1gMyelin SheathSlide 6Synaptic TransmissionSlide 8Figure 48.12 A chemical synapseMotor NeuronsSome Drugs work on receptorsHow did they figure this out?Muscle InteractionSushiPoison DartsSarin1Nervous System2ScopeHumans have 1012 neuronsYou only have 109 DNA basesTypical cells are 10 microns in diameterSome of your neurons are 3 feet longThe longest neurons in Giraffe 3 metersComplex program directs connectionsYou photoreceptors can detect down to 1 photon-70 mV across 3nm is equivalent to 200,000V across 1cm3Animation41s1g domains of Kv4 K(+) channels regulate binding to and modulation by KChIP15Myelin SheathWraps around Multiple Sclerosis is an autoimmune attack on myelin sheaths resulting in 100 times slower signal propagation along the axon6Most neurons have a single axon – a long (up to 1m) process designed to convey info away from the cell body.Transmit APs from the soma toward the end of the axon where they cause NT release.Often branch sparsely, forming collaterals.Each collateral may split into telodendria which end in a synaptic knob, which contains synaptic vesicles – membranous bags of NTs.7Synaptic TransmissionAn AP reaches the axon terminal of the presynaptic cell and causes V-gated Ca2+ channels to open.Ca2+ rushes in, binds to regulatory proteins & initiates NT exocytosis.NTs diffuse across the synaptic cleft and then bind to receptors on the postsynaptic membrane and initiate some sort of response on the postsynaptic cell.89Figure 48.12 A chemical synapse10SpinalCordBrainSensoryNeuronMotorNeuronMotor NeuronsOUTPUT From the brain and spinal cord To the muscles and glands.11Some Drugs work on receptorsSome drugs are shaped like neurotransmittersAntagonists : fit the receptor but poorly and block the NTe.g. beta blockersAgonists : fit receptor well and act like the NTe.g. nicotine.12How did they figure this out?Patch ClampingPut a really small pipette over a ion channelSuck up one ion channel so that the membrane blocks the glass tubeMeasure the current flow as you vary voltage across the ion channelInsert chemicals to see how they impact the channel13Muscle InteractionCalcium channels activated by action potential in nerveCascade through muscle caused by interaction with one muscle cellhttp://thevirtualheart.org/14SushiBlowfish have a toxin that irreversibly binds and inhibits the voltage gated sodium channelsParalyzes person who consumes it because you cant accomplish action potential15Poison DartsTip with CurareReversibly binds to acetylcholine receptor and blocks connection between nerves and muscles16SarinInhibits acetylcholinesteraseYou cant relax your
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