I. Cell Biology of the Neuron1. Describe the cell composition of the nervous system:1000000000000 cells: 10% neurons and 90% glial cells but by cell volume (50:50)2. What are the main parts of a neuron?1. Soma or cell body (nucleus)2. Dendrites: signal inputsignal receiver side of neuron- post synaptic density with neurotransmitter receptorshas spines and shafts3. Axon4. Axon hillock (site of AP generation)5. Synapse: signal output3. Describe the basics of the pre synaptic terminalThis is the site of transmitter release and has mitochondria and vesicles- can make many connections to other cells – not just neurons4. What are the four different types of connections? Explain whether they are excitatory, inhibitory or modulatory1. Axo-dendritic (classical type)a. Spines- excitatoryb. shafts- inhibitory2. Axo-somatic- inhibitory3. Axo-axonic- modulatory4. Dendro-dendritic- rare5. What are the different components that make up the cytoskeleton?1. Actin filamentsstructure, spines, growth cone (smallest)2. Microtubulesbiggest- movement of cargo3. Neurofilamentsmedium- structure6. What are the two types of axonal transport?1. Anterograde: cell body to the nerve terminalassociated with axonal growth and delivery of synaptic vesiclesuse KINESINS (transport motor proteins) (- +)2. Retrograde: nerve terminal to cell bodyinvolves old or worn out proteins and membranestransports to lysosome to be degradeduse DYNEINS (+-)7. What are the types of glial cells?1. Astrocytesstructural support, control K+ and transmitter concentrations, regulate metabolismmain role to remove NT from the synapse2. Oligodendrocytesmyelinate neurons in CNSmultiple neurons3. Schwann cellsmyelinate a single neuronin PNS4. Microgliapart of immune system involved in phagocytosis- not really glia8. How do glial cells differ from neurons?1. Don't form synapses (not same type of communication)2. Have only one type of process (no polarity)3. Retain the ability to divide (neurons do not)4. Are less electrically excitable than neurons (don't really fire AP)9. Describe which neurons are excited and inhibited during the knee-jerk reflexWhen hammer is initially tapped, the sensory neuron fires initially and then the extensor motor neuron starts to fire along with the interneuron (which is inhibitory). The flexor motor neuron however stops firing. This activation of the extensor neuron and inhibition of the flexor neuron is what causes the knee jerk responseII. Experimental Methods in Neuroscience (not a lot covered on exam)1. What is Functional MRI or fMRI?Blood oxygenation is linked with neural activity so this records blood flow indirectly and non invasively1. What are the three model systems for genetic research?1. Knock out animals: delete gene of interest2. Knock-in animals: replace a gene of interest with an exogenous one3. Transgenic animals: insert a copy of exogenous geneIII. The Membrane and Action Potentials1. What is the membrane potential and how is it generated?Electrical voltage difference across the membrane due to higher concentrations of K+ inside the membrane and higher concentration of Na+ outside the membrane2. What is the difference between ion channels and ion transporters?1. Ion transporteractively move ions against concentration gradient with help of ATP- create ion concentration gradients2. Ion channelsallow ions to diffuse down concentration gradient due to selective permeability to certain ions3. What is the Nernst equation?The equilibrium potential of a single ionE(ion)= RT/zF (ln([out]/[in])For monovalent cation: 58 mV in frontFor monovalent anion: -58 mV in frontFor divalent cation: 29 mV in front4. What is the resting potential determined by?Non gated K+ channelsAlways openNa+ has little effect on resting membrane potential5. What affects the action potential?Na+ influx reaching threshold (increase in permeability to Na+)Also delay in opening of voltage gated K+ channels6. Describe the GHK equationThe contribution of all ions to the membrane potentialNote that Cl- values are flipped due to valenceV=58log ((Pk[K]2 +PNa[Na]2 +PCl[Cl]1)/(Pk[K]1+PNa[Na]1+PCl[Cl]2))7. What are the basic steps in the generation of an action potential?1. Non gated K+ channels are open as well as K+/Na+ ATPase generating the resting membrane potential2. Signal reaches and causes increase in permeability of Na+ channels causing voltage gated Na+ channels to open (early currents)3. Once Na+>K+ and threshold is reached AP is generated where there is a rapid increase in Na+ influx4. Delayed opening of voltage gated K+ channels causes K+ to flow out and repolarize the cell. (late currents)5. Voltage gated Na+ channels close while K+ voltage gated channels still open causing undershoot (hyperpolarization)6. Closing of voltage gated K+ channels8. What is capacitive current?Movement of charge within the membrane- ions do not flow when hyperpolarized but do when depolarized (current)9. What is the refractory period?A period of time after the initiation of one action potential when it is impossible to initiate a second action potential no matter how depolarized the cell is.Due to hyperpolarization and Na+ channel inactivation gates – intrinsic properties of voltage gated Na+ channelPrevents AP from going backwards10. Why does voltage dissipate with non action potential current flow?1. Cytoplasm has high resistance2. Membrane isn’t impermeable to some charge leak11. What is the length constant and what affects it?An indication of how far a potential will spread along an axon in response to subthreshold stimuli (the larger the longer the potential will spread)Larger with more resistance across membrane, smaller with more resistance in intracellular and extracellular fluid12. What is the time constant and what affects it?Determines the time course for the change in membrane potential (want small time constant for fast conduction)Smaller with less membrane resistance and less membrane capacitance13. How do you increase the velocity of the AP?1. Increase the diameter of the axon- lowers resistance2. Increase the resistance of the membrane (myelination)- charge wont flow outIV. Ion Channels and Transporters1. What are the different methods for measuring ion channel activity?1. Cell attached recording- tight contact between pipette and membrane2. Whole cell recording- if want to look at multiple channels3. Patch-clamp recording- single channels1. Inside out- the inside of the channel is touching the extracellular fluid2. Outside