!Exam%#%1%Study%Guide%Lectures:%17%6%26%Lecture'17'(September'25th,'2014)'!What%is%the%neuron%doctrine?%Describe%Santiago%Ramon%y%Cajai%and%Camillo%Golgi’s%part%in%it.%%%Neuron%Doctrine%%! The!neuron!doctrine!states!that!the!nerve!cell!is!the!fundamental!structural!and!functional!unit!of!the!nervous!system.!Santiago%Ramon%y%Cajai%! Used!the!golgi!stain!and!was!labeling!a!subset!of!cells.!!This!golgi!stain!was!important!because!it!stained!the!entire!cell.!!!While!using!this!stain!he!only!labeled!1<2!of!the!neuronsàso!he!could!see!without!the!distraction!of!other!things.!!! He!came!to!the!conclusion!that!the!nervous!system!was!composed!of!individual!units!called!neurons!and!that!the!directionality!of!information!flow!was!the:!law'of'dynamic'polarization.!***he!was!right!and!Camillo!Golgi!was!wrong!!Camillo%Golgi%! Worked!with!the!same!stain!as!Santiago!and!they!were!enemies,!he!said!that!the!nervous!system!was!composed!of!neurons!called!cytoplasmic!bridges.!!***they!both!ended!up!getting!the!Nobel!prize!even!though!Camillo!was!wrong!!%%Describe%and%draw%the%basic%structure%of%a%neuron%and%all%of%its%parts.%%%Structural%Organization%of%Neurons%%! <the!neuron!consists!of!many!different!parts!!! ! >dendrite!!! ! >neuronal!cell!body!!! ! >axon!! ! >axon!terminal!!! <protein!synthesis!is!confined!to!the!neuronal!cell!body!!! <the!whole!structure!can!be!up!to!a!meter!long!!! <the!directionality!of!dendrite!cell!body!axon:!dynamic'polarization!!! <there!are!synapses!on!the!end!that!connect!to!the!input!region!!! <input'region:!ligand!gated!channels!response!proportional!to!the!number!of!channels!that!open!!! <conductile'region:!voltage!gated!channels!(all!or!nothing)!!! <AP!propagates!along!the!conductile!region!which!carries!electrical!information!for!long!distances!!!!!''''''BMS'300''''1nd'Edition'! !! <they!are!very!unusual!because!they!are!asymmetric!!!Lecture'18'(September'26th,'2014)'!What%is%a%glia%cell?%What%are%its%two%types%and%what%do%those%do?%%%Glia!! Glia!cells!are!cells!of!the!nervous!system!that!act!as!glue.!!They!are!cells!that!hold!the!nervous!system!together.!!In!the!CNS!glia!are!essential!for!regulating!the!environment!in!which!neurons!function.!!They!come!in!two!different!varieties:!! ! >astrocyte!!! ! ! 1.!regulates!the!extracellular!K+!concentration!(at!about!4<5mmol)!! ! ! 2.regulates!the!neurotransmitter!concentration!at!synapses!!! A!synapses!is!when!they!go!from!the!output!region!to!the!input!region.!!The!output!region!releases!a!neurotransmitter!into!the!synaptic!cleft!and!basically!binds!the!neurotransmitters!at!the!input!site!and!vacuums!them!together.!!! ! >oligodendrocyte!! ! ! 1.milanation:!they!wrap!conductile!regions!of!neurons!with!concentric!rings!(layers)!of!plasma!membrane!that!we!call!myelin!(laid!down!in!layers)!!!! This!happens!early.!!The!oligodendrocyte!sends!out!a!process!that!allows!it!to!stick!to!the!plasma!membrane!of!the!axon!but!it!doesn’t!stop,!it!then!continues!to!send!an!extension!around!the!cell.!!The!leading!edge!insinuates!itself!under!the!first!layer!and!breaks!the!bonds!between!the!two!membranes.!!After!a!while!there!is!a!structure!that!goes!around!and!around!! !and!it!will!go!back!around!to!the!oligodendrocyte.!!We!will!then!use!it!to!send!out!a!process!to!generate!an!insulating!layer.!A!schwann!cell!does!pretty!much!the!same!thing.!!EXAMPLE:!multiple!scrosis:!all!manner!of!problems!with!the!nervous!system!!! ! >disease!of!the!oligodendrocytes!!! ! >you!recover!and!it!is!a!progressive!degenerative!disease!because!your!body!won’t!fully!heal!after!each!attack!!! ! >the!longer!the!interval!in!between!each!attack!the!better!the!diagnosis!is!!How%are%neurons%electrically%excitable%cells?%How%do%we%create%a%“battery”?%!Neurons%as%electrically%excitable%cells%%! We!are!generating!a!potassium!battery!where!we!separate!electrical!(ions)!charge!across!a!membrane!to!generate!an!electrical!potential!that!stores!energy!and!can!do!work!(like!putting!a!battery!in!your!phone).!!! When!we!do!this!on!the!inside!of!a!plasma!membrane!place!100mmol!K+!ions!on!the!outside!we!have!10mmol!K+.!!We!then!put!some!transmembrane!proteins!“potassium!leak!channels”!but!we!don’t!have!a!selective!hydrophilic!pathway,!meaning!it!won’t!be!long!before!we!reach!equilibrium.!!This!is!diffusion!of!potassium!down!its!concentration!gradient.!!! <the!reality!is!that!on!the!inside!of!the!membrane!there!are!large!impermant!anions!!! ! >can!be!proteins,!acids!etc.!! ! >negatively!charged!! ! >big!! ! >can’t!leave!the!cell!!! Potassium!is!a!cation!and!the!large!anion!is!negative.!!Basically,!the!potassium!will!start!running!down!concentration!gradient!until!their!movement!is!held!in!check!by!the!anions!which!will!form!the!potassium!equilibrium!potential.!!!! ! >Nerust!!! ! ! <the!nerust!potential:!the!equilibrium!potential!for!potassium!is!!! ! ! <equilibriums!for!potassium!is!61.5!log!(K+(outside)/K<(inside))!! ! ! <in!bio!the!numbers!aren’t!that!simple!IMPORTANT!TO!KNOW:!!**we!have!generated!a!battery!across!a!membrane!in!a!way!that!there!is!more!negative!on!the!inside!!**storing!energy!across!a!membrane!!**we!have!made!a!battery!that!is!stable!and!doesn’t!change!so!it’s!not!very!useful!for!signaling!!!!! !'Lecture'19'(September'29th,'2014)''Describe%the%different%steps%of%action%potential.%Draw%out%what%happens%when%an%action%potential%occurs.%%%Action%potential!! STEP!1:!Resting!!! ! <all!v<gated!channels!are!closed!!! ! <ion!permeability:!K+!due!to!the!K+!leak!channels!! ! <action!potential!curve:!flat,!<70mv,!around!the!Ek!! STEP!2:!Depolarization!!! ! <the!Na+!v<gated!channels!are!open!!! ! <ion!permeability:!Na+!flows!into!the!cell!!! ! <action!potential!curve:!sharp!upward!curve!(approaching!Ena=40mv)!! STEP!3:!Repolarization!!! ! <the!Na+!v<gated!channels!inactivate!because!of!the!ball!&!chain!and!the!K+!channels!are!open!!! ! <ion!permeability:!K+!flows!out!of!the!cell!down!the!concentration!gradient!! ! <action!potential!curve:!downward!curve!approaching!the!Ek=<80mv!! STEP!4:!Hyperpolarization!!! !! ! <some!of!the!K+!v<gated!channels!are!open!and!the!Na+!v<gated!channels!reset!!! ! <ion!permeability:!K+!! ! <action!potential!curve:!below!the!resting!potential!(<70)!so!it’s!around!<80mv!!! ! which!is!the!Ek!%!Lecture'20'(October'1st,'2014)''What%are%the%rules%for%propagating%a%regenerating%action%potential%on%an%unmyelinated%neuron?%%Propagating%a%regenerating%action%potential%in%an%unmyelinated%neuron%%!
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