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Neurosciences 1.6 -- Ionotropic Signaling


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what is the excitatory transmitter that mediates fast inotropic signaling in the CNS?
what are the three groups of ionotropic receptors?
AMPA, kainate and NMDA
what are the non-NMDA receptors and what do they produce?
AMPA, kainate

produce fast EPSPs
what happens when non-NMDA receptors are activated by L-GLU?
causes a rapid inc in permeability to Na and K ions and an EPSP
T/F in fast ionotropic signaling (non-NMDA receptor) there are two transmitter binding sites and both must bind transmitter for the channel to open
fast inhibitory ionotropic signaling is mediated by what?
GABA or Glycine-gated Ion Channels
how many subunits to GABA-gated channel?
three: alpha, beta, gamma
where is the glycine-gated ion channel found?
only in the spinal cord and brain stem
what happens upon activation of GABA or glycine receptors?
inc chloride conductance across the PM
how does IPSP reduce amplitude of EPSP?
opening inhibitory chloride ion channels inc the conductance of the nerve membrane, therefore reducing the amplitude of the EPSP (V=I/G)
what are the three different types of modulators that can influence GABA-ergic inhibition?
benzodiazepines (BZ), barbituates, and neurosteroids

these inc the cholride current that flows when GABA opens GABA-gated-Cl- channel
has tranquilizing (antianxiety), muscle relaxant and antiepileptic actions
deficiency of pyridoxal leads to what?
less production of GABA, leads to convulsions
name three convulsants (antagonists of GABA)
bicuculline, picrotoxin, strychnine
why is it that APs are generated at the axon hillock?
b/c at the axon hillock there is a high density of voltage-gated sodium channels --> therefore threshold at the axon potential is the lowest
compare the location of excitatory and inhibitory synapses
excitatory synapses generally occur on distal dendrites and their dendritic spines

inhibitory synapses are found on proximal dendrites or on the cell body
synaptic divergence
one synaptic bouton makes fxnal contact with dendrites from two or more postsynaptic neurons
synaptic convergence
synaptic terminals from multiple presynaptic neurons converge on a single postsynaptic neuron allowing integration of signals from multiple sources
presynaptic modulation
transmitter released at an axoaxonic synapse regulates the amount of transmitter released from the target terminal in response to an AP
feedforward inhibition
synaptic terminal excites the postsynaptic neuron via an axodendritic synapse as well as an inhibitory synaptic terminal that also innervates the same postsynaptic spine

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