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Flashcards in Synaptic Transmission Deck (23)
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highly receptive area with large surface area
-receptors for transmitters
-voltage-gated ion channels amplify graded synaptic signal
-primary areas for receiving and integrating complex info from thousands of synapses


cell soma of neurons

surrounds nucleus and contains organelles for house-keeping functions
-membrane contains receptors for chemical transmitters


axon of neurons

single thin process arising from cell body at axon hillock (loaded with voltage gated Na+ channels)
-transmits all-or-none APs to terminals after integrating changes
-can be a meter+ in length with axoplasm-like cytoplasm (cell body)
-usually surrounded with myelin sheath


presynaptic terminals

specialized structures that convert electrical signals propagated down axon (APs) into chemical signals (nt) released from presynaptic vesicles and trasmitted to target at the synapse


difference between postsynaptic potentials and action potetions

postsynaptic potentials are small graded changes



contains parallel arrays of microtubules and neurofilaments
-kinesin: anterograde from soma to terminal
-dynein: retrograde from terminal to soma


electrical synapses background info

electrical response in one cell is transmitted to another
-extremely fast (little/no delay) and bidirectional passive flow between gap junctions
-less common than chemical synapses in nervous system


criteria for chemical neurotransmitters

1. present in presynaptic terminal
2. released in voltage- and Ca+ dependent manner
3. specific receptors present in postsynaptic target cell
4. means to inactivate the transmitter (enzymatic breakdown, re-uptake, GABA inhibitors, etc.)


steps in a chemical synaptic transmission

1. transmitter molecules are made and packaged in vesicles
2. AP arrives at presynaptic terminal
3. depolarization of terminal opens voltage-gated Ca+ channels
4. increased Ca++ in terminals trigger vesicle fusion
5. transmitter diffuses across cleft and binds to postsynaptic receptors
6. postsynaptic response occurs
7. transmitter molecules are cleared/inactivated by enzymatic degradation, uptake, or diffusion


what happens if neurotransmitters are not cleared in synapse?

initially a "high" but then will be desensitized after a long period of time
-receptors are internalized, etc.


active zones of presynaptic terminals

docking site for transmitter-containing vesicles
-preferentially released in response to AP, Ca+ influx


postsynaptic density

electron dense area with many neurotransmitter receptors in postsynaptic cells
-aligned with presynaptic active zones to promote efficiency


functional magnetic resonance imaging for synapses

measures changes in regional blood flow associated with changes in local cerebral glucose metabolism


exocytosis and vesicle fusion

regulated by Ca++ (binds to V-SNARES) and endocytosis (to prevent enlargement of presynaptic membrane)


are synaptobrevin, synaptotagmin, and syntaxin V-SNAREs or T-SNAREs?

synaptobrevin and synaptotagmin are v-SNAREs
syntaxin is a t-SNARE


two classifications for postsynaptic receptors

ionotropic - have ligand-gated ion channel (usually Na/K)
-nicotinic (nicotine can selectively activate it)
metabotropic - linked to G-PRO that transduce slower biochemical signal
-muscarinic (muscarin can selectively activate it)


how are postsynaptic potentials produced?

conductance changes due to ion channel openings/closings lead to ionic current flow thru channels that lead to changes in membrane potential


what is the major excitatory neurotransmitter for EPSPs? and relation to AMPA and NMDA

glutamate - binds to both ionotropic and metabropic receptors for depolarization
-AMPA receptor channels - mediate fast EPSP via flow of Na/K down gradients
-NMDA receptor channels - mediate slower EPSP via flow of Na/K/Ca
--typically don't open unless sufficiently depolarized b/c blocked in voltage-dependent manner by Mg


what is the major inhibatory neurotransmitter FOR IPSPs? and difference between GABA-A, GABA-B

GABA - binds to both ionotropic and metabotropic receptors for hyperpolarization
-A: mediate fast IPSP via flow of Cl- down gradient
-B: slower IPSP b/c G-PRO linked receptors



drug that elicits larger IPSP when GABA is present b/c increases channel open time/singl channel current


synaptic bouton

branches of terminal regions of axons
-myelination lost if in close contact with dendrite or cell body of another neuron, and when they fuse neurotransmitters are released


cable theory

temporal and spatial effects of summation
-potential can be lost via decremental conduction


which conditions allow summation? long or short time constants or space constants?

longer time and space constants allow for summation
-shorter constants usually terminate before they can summate

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