Neuro PDF - Biology Exam Notes

Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...

Summary

These notes describe the central and peripheral nervous systems, including neurons, axons, and synapses. They cover details about action potentials and neurotransmission.

Full Transcript

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

Use Quizgecko on...
Browser
Browser