Neuro PDF - Biology Exam Notes

PNS - Newes afferentneurons , : sensory infotCNs, efferent neurons :...

PNS - Newes afferentneurons , : sensory infotCNs, efferent neurons : motor info from braine PNS CNS - Spinal cord , brain frontal , parietal occipital temporal : , , , gray matter-cell bodies , white matter-myelin-axons - Neuron Nucleus : Chromosomes(DNA) - Genes-Geneexpression cell body - = soma terminal collaterals, terminal hillock-proper synaptic vesicles contact site Axon Away : - axon , : , , = - Cytoskeleton - microtubules : dynamic, plastic - neurofilaments : Stable abundant , micro filaments : plastic, dynamic, near molecules plasma - membrane , actin ~ Axoplasmic Transport (from - antenograde : soma-axon , Kinesins Ask-anterograde , soma , Kinesin - retrograde : axon + some , dynein - carries organelles resides RAD-retrograde ,. So, dynie - Cell Types I - Microglia phagocytes : , immune cells - Ependyma : line spinal corda rentricles of brain S - Oligodendrocytes : myelinate CNS axons, structure - Astrocytes : blood brain barrier - fill most of the space between neurons in the brain ↳ limits k" movement & -Schwann alls : myelinate neurons in PNS - Membrane Potential - voltage (Vm) - depends on ion concentration difference in electrical potential across cell membrane-ion concentration gradient, selective permeability 65mV Vm 0 Chyperpolarized() - = potent difference murons & rest have UmF-60 -70 mV · , no , , · Nat (+ 60) outside , K + (81) inside > Ap reversal of - = potential Forces (Diffusion) · membrane ↑ permeable to Chemical diffusion > - concentration gradient, permeability of membrane K+ but steady leak of Na in : Electrical opps attract potential dif voltage 65 mu potential v : , = conductance = - ↑ ↳ Ohms law V : = IR (current resistance) > - gion =tion , F = gV (current = conductance potential) ↳ Driving Um-Eion 0 current, P outwardcurrent, O inward current force : Eion equilibrium pot , no = Nernst Equation Ex = log237- ions flow until reaching this 5 : · charge of ion Pion [ion]o + Pion (ion]o p & Goldman Equation : Um = 61. 5 mVlog = permeability Kt Pion [ion] : + Dion Lion) : Nat · Depolarization Um getting less negative : · current : flow of ions - I compreability 9 Hyperpolarization Um getting more neg - : · : how easy it is tme o a · Current inward-less neg depolarization : , , (t) in , C out , outward more neg, hyperpol (t) - , out , (t in E based on - - cations voltage gated voltage gated TTX blocks Nat currents TEA blocks K" currents , - For Dumps · Sodium-Potassium : enzyme that breaks down ATP in presence of internal Nat Cation : ion w/ pos charge ↳ exchanges inside Nat for outside Ke againsttheir conc. gradients · Anion : ion w/ veg charge Calcium pump : enzyme that active transports (at from cytosol e membrane rest membrane pot. Wouldn't exist wyout - Voltage Gated - Channels blocked by ball + chain M · Sodium : open w/ little delay stay , open for Imsec then close (inactivate) can't be opened again until Um returns to , threshold ↳ TTX dogs pore stops AP - Potassium Imsec lets kt leave cell open after : , ↳ TEA blocks currents Refractory Periods - · Absolute impossible - for AP to fire -> Nat channels are inactivated , 1st then comes · Relative difficult - for AP to fire , membrane is returning to threshold mV ↳ means AD can't turn around  + 55 -ondstand eas quick then deactivates 64 reaching + 55m is · K activates slowly but keeps ↑ - Voltage Dependent both W/rising depolarization · : Action Potential - lasts / msec-naturally Stimulus neurotransm experimentally : , , : current in celle clamps 1. Neuron depolarized to threshold vol-gated Nat channels - & Nat perm open. 2 Nat rushes into cell - more depol > more - Nat channels open - positivefeedback + 3 K. channels opena kt perm ↑ - leaves cell - repolarizes back to rest both o because of ↓ membrane potential V Why gates are needed & ACTION POTENTIAL - Sodium When cell is resting wants in potassium , out 1 Threshold Um. : where enough gated Nat channels are open PNa > Dr 2. Rising Phase large driving : force on Nat- > rushes into - cell becomes more depol. Overshoot Um 3 inside is pos here Ena Reaks & 40 mv : approaches , , grepol 4 Falling Phase V-gated Not channels gated "channels open -k rushes out of cell +. : inactivate , - open (-87mU) hyperpol. Undershoot 5 Um Lbecomes E approaches En kt channels : e more as remain -Speed Factors : want tr internal resist , ↑ mem. resist = ↑ axon diameter , myelination · Exon diameter - ↑ diameter d > fewions touch mem internal resistance -., little current leaks = faster Myelination ↑ resistance · - mem. ↳ saltatory conduction AP jumps from : mode to n Nor faster AP @ conduction & - Synaptic Transmission : Chemical +electrical fastest bidirectional Electrical synapse ion channels of post synaptic cell-cellsare electrically coupled · : connect cytoplasm pre + depolarizing it, I ↳ Some current flows thru a resist, I conduct channels between pret postsynaptic cells , ↳ gap junctions , direct transfer of current · Chemical synapse : neurons separated by synaptic cleff delay about 1-5mse 4 pol ↳ ↑ resist of AP release of demical transmitter e interacts w recepts no currentcrosses postsynaptic mem , ed pol ↳ pre + postsynaptic cells NOT connected , Synaptic cleft extracellular space , synaptic vesicles Gap junction channel & exteriticallysyapsapes? : Chem Synapses Gray's Type I-asymmetric : , round resides , excitatory ↓ ↳ Gray's Type ll-Symmetric , flat resicles, inhibitory - 1. pre-synaptic depol reaches threshold 2 Ap. generated 3 synaptic. terminal depol 4. - Receptors : receptors have 2 major functions : recognikatblared taschitter? attipage?effector proteins (receptors effectors + ligand-gated channels several : protein subunits form both transmitter binding site d ion channel IPSP ↳ ex Nicotinic ACh receptor, AMPA type flu EPSP receptor e effector, ionotropic receptors -. receptor , GABA-A receptor (NT) · contropic receptors : Channels that allow Di Nat , K+ + Ca in response to binding of a chem messenger. GABA-A channel only Cl , less likely conducts to fire AP synapse inhibitory IPSP-inhibitory post , = , synaptic potential G · nACh + AMPA channels conduct NatkT , likely to fire AP Synapse excitatory more EPSP : excitatory currenta : = , , Neurotransmitters post synaptic potential X channel reversal potential : when mV = 0 Ever is in between EnatEr for a Um > Conducting Nat & K + Vm > EverErev - current terminal : synthesized a stored in presynaptic neurol , released by presynaptic axon outwards Cholinergic synthesize acetylcholine. Choline acytltransferase (ChAT), Vesicular ACh transporter, Acetylcholinesterase (AChE), Choline transporter. neurons : eX v - & Glutamergic receptors : ↳NMDA ↳ receptor: both coincidence detector atastes : channel only opens when both Pres removed by depol AMPA receptors mediate initial depole , channel opening WhyAMPA WMAA is activity dep ne ↓ elements releasing post synaptic are active glutamate ↳ depol so Mgt block is removed - Nata Cat enter postsynaptic cell - activates enzymes regulates channels , · G-protein-coupled receptors receptor : protein that binds transmitters is distinct from ion Channel - ↳ receptor coupled to effector by 6-proteins receptor effector , , metabotopic receptors effector protein Metabotropic receptors is either enzyme · : an ion channel an -slow ↳ 2nd enzyme Synthesizes : messenger ↳ 1st messenger NT : ↳ Shortcut pathway : primary effector : ion channel - > ↳  large major neurotransmitter systems 2 : classes - small mol-ACh , amino acids , biogenic amines ; peptides : AAs ↳ small mol : AA-glutamate , GABA, Glycine ; Amines-nor- epinephrine , dop- histamine Serotonin ACh-in , , , , axon terminal ↳ large ty by peptide : mols of At strung ribosomes in rough ER not transm action of chemical messenger Postsynaptic cell depends on properties of receptor · on , agonisifferemibetween ofatransit anaguintf blocks action of transm · :. neuromuscular junction used to study directly gated synaptic transmission : be muscle cells are large Chemical Transmission : Voltage-gated Ca2"channels in the ↳ - ↳ terminal Ca* +necessary for reside fusion - , Synthesise synapticvesiclesfusion NTesynaptic cleft , , NTepostsynapticreceptsa removal of NT from synaptic cleft in cell Exo Cytoslifsferentasseforethanesm Emodcy Kostosisprense transm.reside -. each transm. released in discrete packets called quanta - holds / quanta Neurotransm recovery + degradation : ·. ↳ reuptake transm term re-enters presynaptic axon :. ↳ diffusion : away from the synapse ↳ destruction inside terminal cytosol synaptic cleft enzymatic or Synaptic Integration - Fneuronalcirclipsensominputs motorouttMos Convergence most cells receive inputs from than E cell · : more Integration of inputs on dendrites. · & a · Ap initiation - axon hillock , impulse conduction-saltatory conduction on m yel inated axons , transmitter Secretion summation - us when inputs from same synapse lead to enough depol to reach threshold Spati 1 & - multiple distinct inputs fire & same time to cause enough depol to reach threshold subthreshold signals decay / distance presynaptic inhibition ↓ amnt of depol : in presynaptic terminal , specific - aimed & excitatory inputs inhibition : affects all inputs not specific postsynaptic -> shunting inhibition : most effective type - SNARE Proteins bring : membrane of the synaptic vesicle + the presynaptic membrane close together V-SNARE (synaptobrevi resicle membrane · +-SNARE (syntaxi N(n the plasma membrane · f-SNARE(SNAP 25)· - in the plasma membrane · Synaptotag min - s Cal C imm Sensor - Research Strategies - Optogenetics - Current clamp light activates light called opsin inject voltage measures voltage · responsive neuron - - Voltage clamp - Patch Clamp · clamps voltage - measures current allows measurements from Single channels