Psych 454 1st Edition Exam 1 Study Guide Lectures 1 12 Lec 1 I Brain cells A 2 main types 1 neurons signal changes in environment internal states etc a 100 billion in brain 2 glia a astrocytes regulate chemical content of extracellular space b oligodendrocytes and Schwann cells insulate axons of neurons 3 other types ependymal cells microglia vasculature B parts of a prototypical neuron 1 cell membrane lipid bilayer that contains proteins 2 dendrites receive input from other neurons part of synapses postsynaptic 3 axon provides input to other neurons a axon terminal part of synapses pre synaptic b axon hillock site of action potential generation c connected by synapses 4 cell body soma II Ions currents and membrane potentials A Electrical theory basis 1 Important ions for neuronal signals sodium Na potassium K calcium Ca2 chloride Cl 2 Electric field created in space around and sources a Opposites attract like repels like 3 Electric potential E needed to move ion towards source of electrical field a ion has more electrical potential at site closer to source 4 Potential difference difference in electric potential E btwn two sites a Volts V E per unit charge neurons usually in mV 5 Current movement of charged particles B Ion concentration gradient across cell membranes 1 Cell membrane separates ions 2 Concentration gradient diff conc of ions inside and outside of neuron a Ions flow from high to low conc site 3 Ion channels selectively permeable to particular ions C Membrane potential electric potential difference btwn inside and outside of cell reflects charge separation across cell membrane D E F G 1 Resting membrane potential inside is more neg than outside usually btwn 65 to 70mV 2 When channels open ions move across membrane a Movement depends on electric potential difference 3 Depolarization membrane potential becomes less more 4 Hyperpolarization membrane potential beomce more Two factors drive ions across cell membrane 1 Movement of ions determined by a Concentration gradient b Membrane potential 2 Ions will diffuse evenly if there are no other driving forces a diffusion direction down concentration gradient 3 Equilibrium potential Eion electrical potential difference that exactly balances ionic conc gradient 4 K key determinant of resting membrane potnential a Resting membrane potential close to EK bc membrane is mostly permeable to potassium at rest Ion channels opened by different methods 1 Voltage gated ion channel a Channels open at particular membrane potentials b Ex Sodium channel potassium channel 2 Ligand gated ion channel a Opened by transmitter messenger ligand b Ex AMPA glutamate receptor GABA receptor Membrane potential threshold critical value of membrane potential at which Na channels open generating an action potential 1 Na channels open when membrane depolarizes a Channel open for 1ms b Channel cannot be immediately opened for 1ms c Absolute refractory period channel inactivated Action potential spike rapid change in membrane potential 1 all or nothing event from 70mV to 30mV and back to 70mV 2 carries information long distance along axon to connected cells 3 phases of action potential a depolarizing phase sodium channels open inward sodium current b hyperpolarizing phase a sodium channels close b potassium channels open c outward potassium current resets potential c concentration gradients reduced a must be reestablished to continue generating action potentials III d sodium potassium pump transposts Na and K against their conc gradient consumes ATP a 70 of brain s E use 4 action potential travels from axon hillock to axon terminal orthodromic direction a sodium influx depolarizes membrane of next membrane to threshold chain reaction b action potential spreads along membrane with conduction velocity c can also travel towards cell body antidromic Lecture Summary A Cell membrane separates ions 1 Extracellular sodium 2 Intracellular potassium B Electrical potential difference across cell membrane 1 Resting membrane potential more neg inside cell than outside cell C Action potential generated when cell depolarized to threshold 1 Sodium channels open Na influx 2 Potassium channels open K efflux membrane potential repolarizes D Action potential transmitted across axon to next cell across synapse Lec 2 I II Different neural signals A Single neuron single unit recordings B Intracellular recordings 1 Action potentials from targeted cell 2 Subthreshold membrane potential fluctuation C Extracellular recordings 3 Action potentials spikes from nearby cells 4 Sort spikes based on size to individual cells to differentiate where action potentials are coming from 5 Subthreshold fluctuations summed from nearby cells 1 Subthreshold is below V required for action potential 6 LFP local field potentials helps gauge local cell s activity What we measure with different recording techniques D Electrode types used in extracellular recordings 1 Classical 2 Matrix multiple classical electrodes 3 Laminar probe multiple electrode contacts 4 Utah array 10x10 electrodes that can be implanted E Size and shape of electrode contact or tip is important F G H I 1 Small exposed metal contact has high resistance 2 Smaller the exposed metal contact or electrode tip smaller the brain area that is sampled Electrode impedance 1 Impedance measure of resistance plus electrode capacitance a Capacitance the ability to store charge 2 Smaller the electrode contact or tip higher the electrode impedance 3 Fine metal tip needs to be w in 10 s of microns from neuron to record spike Local field potential LFP recordings 1 From extracellular depth electrode a Reflects up to 1000 cells b Derived mainly from w in 250 microns of electrode tip 2 From electrocorticography ECoG a Intracranial recordings b Performed to localize seizure activity c Electrodes on exposed brain surface subdural d Derived from superficial layers of cerebral cortex e Clinically used for epilepsy patients Electroencephalophagry EEG 1 Signals reflect 100s of thousands to millions of cells 2 Summation of synchronized activity of neurons with similar spatial orientation 3 Predominantly derived from pyramidal cells in cortex 4 Noninvasive electrodes above scalp 5 Source localization degraded by skull 6 Deep brain structures inaccessible 7 Poor spatial resolution but good temporal resolution Functional magnetic resonance imaging FMRI 1 Signals excite H atoms with magnetic fields 2 Measure emitted radio frequency signal 3 Indirect measure of