synaptic plasticity Flashcards
does electrical activity aid synapse formation?
No, Synapses form in the absence of electrical activity, and are guided by molecular guidance cues instead.
“Neurons that fire together wire together.”
Pre-synaptic firing that synchronizes with strong post-synaptic activation strengthens synapses.
“Neurons that fire out of synch lose their link”
Pre-synaptic firing that does not synchronize with strong post-synaptic activation weakens synapses.
Ionotropic Glutamate receptors in the CNS
allow positively charged ions to enter the cell, helping depolarize it.
Three main types of Ionotropic Glutamate receptors in the CNS.
– NMDA – AMPA – Kainate
Metabotropic
are not themselves ion channels but influence cells via G-protein coupled activities.
Glutamate receptors at the synapse
Pre-synaptic neurons release glutamate, activating post-synaptic glutamate receptors (ionotropic and metabotropic).
co-incidence detectors
another term for an NMDA receptors
what type of ions block the NMDA receptor channel at normal resting potential?
Magnesium ions
what happens to NMDA receptors when the membrane is depolarized?
magnesium is displaced and positive ions, including calcium, can enter.
Silent synapse
a synapse with only NMDA receptors (no AMPA).
Early on, most synapses only express NMDA, with no AMPA. Over time AMPARs become integrated into the synapses.
cell death is an ______ process
active
How are synapses strengthened?
long term potentiation
how are Synapses strengthened by long term potentiation?
At specific synapses, discrete stimuli (often high frequency stimulation) causes synaptic strength to increase.
LTP is input specific to the stimulated synapses, not a general activation of the post-‐synaptic neuron. (only strengthens those specific synapses which fired frequently)
LTP in the hippocampus requires the function of what glutamate receptor
NMDA
What flows into the cell during LTP that signals for new AMPA receptors?
Calcium flowing into the cell signals for the insertion of more AMPARs into the post-synaptic membrane.
This strengthens the synapse
NMDA receptors have a critical quality that enables them to contribute to LTP. What is it?
in addition to being permeable to Na+ they are also permeable to Ca++.
Calcium entry into the post-‐synaptic cell activates critical post- synaptic events, including activation of ______.
‘kinases’
Long term depression
the weakening of poorly correlated synapses
LTD is the weakening of a specific synapse in response to discrete input stimuli.
LTD, like LTP, relies on _______
calcium influx
High magnitude and short calcium influx activates ______, while low magnitude and a long duration of calcium influx activates.
kinases (LTP).
phosphatases (LTD)
The induction of LTP or LTD seems to be determined by __________.
the frequency and intensity of calcium entry.
Human temporal lobe neurons show what type of synaptic plasticity?
bi-‐directional.
Bi-directional synaptic plasticity.
low frequency stimulation leads to LTD, while high frequency stimulation leads to LTP.
These types of stimulation are physiologically relevant, suggesting human cortical neurons are capable of experiencing LTP/LTD.
