Psych 454 1st EditionExam # 1 Study Guide Lectures: 1 - 12Lec. 1 I. Brain cells A. 2 main types: 1. neurons – signal changes in environment, internal states, etca) 100 billion in brain2. glia :a) astrocytes - regulate chemical content of extracellular space b) oligodendrocytes and Schwann cells – insulate axons of neurons 3. other types: ependymal cells, microglia, vasculatureB. parts of a prototypical neuron1. cell membrane – lipid bilayer that contains proteins2. dendrites – receive input from other neurons; part of synapses (post-synaptic)3. axon – provides input to other neurons a) axon terminal – part of synapses (pre-synaptic)b) axon hillock – site of action potential generationc) connected by synapses4. cell body (soma) II. Ions, currents, and membrane potentialsA. Electrical theory basis1. Important ions for neuronal signals: sodium (Na+), potassium (K+), calcium (Ca2+), chloride (Cl-)2. Electric field – created in space around + and – sourcesa) Opposites attract; like repels like3. 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 mV5. Current – movement of charged particles B. Ion concentration gradient across cell membranes 1. Cell membrane separates ions2. Concentration gradient - diff. conc. of ions inside and outside of neurona) Ions flow from high to low conc. site3. Ion channels selectively permeable to particular ionsC. Membrane potential – electric potential difference btwn inside and outside of cell; reflects charge separation across cell membrane1. Resting membrane potential: inside is more neg. than outside; usually btwn -65 to -70mV2. When channels open, ions move across membranea) Movement depends on electric potential difference3. Depolarization – membrane potential becomes less - (more +)4. Hyperpolarization – membrane potential beomce more –D. Two factors drive ions across cell membrane1. Movement of ions determined by:a) Concentration gradientb) Membrane potential 2. Ions will diffuse evenly if there are no other driving forces a) diffusion direction down concentration gradient3. Equilibrium potential (Eion) – electrical potential difference that exactlybalances ionic conc. gradient4. K+ key determinant of resting membrane potnential a) Resting membrane potential close to EK bc membrane is mostly permeable to potassium at rest E. Ion channels – opened by different methods1. Voltage-gated ion channela) Channels open at particular membrane potentialsb) Ex. Sodium channel; potassium channel2. Ligand-gated ion channela) Opened by transmitter/messenger (ligand)b) Ex. AMPA glutamate receptor; GABA receptorF. Membrane potential threshold – critical value of membrane potential at which Na+ channels open, generating an action potential 1. Na+ channels open when membrane depolarizesa) Channel open for 1msb) Channel cannot be immediately opened for 1msc) Absolute refractory period – channel inactivatedG. Action potential (‘spike’) – rapid change in membrane potential1. ‘all or nothing’ event: from -70mV to +30mV and back to -70mV2. carries information long distance along axon to connected cells 3. phases of action potential:a) depolarizing phase: sodium channels open  inward sodium currentb) hyperpolarizing phase: a. sodium channels close b. potassium channels openc. outward potassium current resets potentialc) concentration gradients reduced a. must be reestablished to continue generating action potentialsd) sodium-potassium pump transposts Na+ and K+ against their conc. gradient; consumes ATPa. 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 velocityc) can also travel towards cell body (antidromic)III. Lecture SummaryA. Cell membrane separates ions1. Extracellular – sodium2. Intracellular – potassiumB. Electrical potential difference across cell membrane1. Resting membrane potential: more neg. inside cell than outside cellC. Action potential generated when cell depolarized to threshold 1. Sodium channels open  Na+ influx2. Potassium channels open  K+ efflux  membrane potential repolarizesD. Action potential transmitted across axon to next cell across synapse Lec. 2 I. Different neural signalsA. Single-neuron (single-unit) recordings B. Intracellular recordings 1. Action potentials from targeted cell2. Subthreshold membrane potential fluctuationC. Extracellular recordings3. Action potentials (spikes) from nearby cells 4. Sort spikes based on size to individual cells – to differentiate where action potentials are coming from5. Subthreshold fluctuations summed from nearby cells1. Subthreshold is below V required for action potential6. LFP – local field potentials – helps gauge local cell’s activity II. What we measure with different recording techniques:D. Electrode types used in extracellular recordings 1. Classical2. Matrix – multiple classical electrodes3. Laminar probe – multiple electrode contacts4. Utah array – 10x10 electrodes that can be implanted E. Size and shape of electrode contact or tip is important:1. Small exposed metal contact has high resistance 2. Smaller the exposed metal contact or electrode tip, smaller the brain area that is sampledF. Electrode impedance1. Impedance – measure of resistance plus electrode capacitance a) Capacitance – the ability to store charge2. 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 spikeG. Local field potential (LFP) recordings 1. From extracellular depth electrode:a) Reflects up to 1000 cellsb) Derived mainly from w/in 250 microns of electrode tip2. From electrocorticography (ECoG)a) Intracranial recordings b) Performed to localize seizure activityc) Electrodes on exposed brain surface (subdural)d) Derived from superficial layers of cerebral cortex e) Clinically used for epilepsy patients H. Electroencephalophagry (EEG)1. Signals reflect 100s of thousands to millions of cells2. Summation of synchronized activity of neurons with similar spatial orientation3. Predominantly derived from pyramidal cells in cortex4.