Week 3 Review Flashcards
Tetanic Stimulation
high frequency repetitive stimulation
the strength of the synapse is referred to as
synaptic efficiency or synaptic weights
LTP
long term potentiation: form of synaptic strengthening (potentiation) observed after tetanic stimulation & lasts for many minutes, hours, even days
LTD
long term depression: form of synaptic weakening (depression) that can last many hours; best studied in cerebellum but also occurs @ synapses of other brain regions
NMDA-type glutamate receptor
ionotropic type of glutamate receptor that, can be opened by glutamate only when postsynaptic cell is depolarized well above resting potential (-70mV)
magnesium block
near neuron’s resting potential, the ion-conducting pore of the NMDA receptor tends to be blocked by magnesium ions
Hebb’s rule
idea that synapses are strengthened only when their (presynaptic) activity coincides with postsynaptic activation (depolarization); as a result “neurons that fire together, wire together”
AMPA receptor
ionotropic type of glutamate receptor that can be opened by glutamate when postsynaptic cell is near its resting potential
which of the following is a special feature of the NMDA glutamate receptor?
a) has very high affinity for glutamate so transmitter remains around for long time
b) bound glutamate does nothing if postsynaptic membrane is not depolarized enough
c) it’s clogged w Mg++ ion that can only be dislodged by strong postsynaptic depolarization
answer: all are correct
which of the following is thought to play a role in LTP?
a) glutamate receptors
b) CaMKII
c) calcium
answer: all are correct
you are experimenting on 3 neurons in a brain slice that obey Hebbian Principles of synaptic plasticity. Neurons 1 & 2 form separate synapses onto Neuron 3. Which neurons must fire to increase synaptic strength at the Neuron 1- Neuron 3 synapse?
b) 1 & 3
in a hebbian synapse, if Neuron A fires & Neuron D is depolarized by an electrode (so that combined depolarization is above threshold) then which of the following would occur?
b) only synapse 1 would be strengthened (synapse between neurons A & D)
Hebbian learning can be described by the phrase; “neurons that fire together, wire together” which means?
b) synaptic connections are strengthened by neuronal activity
Synaptic scaling is a phenomenon where
a) neurons adjust their sensitivity to stimuli dependent on their activity
In an experiment, you find that cortical neurons that have not been exposed to glutamate for several days give far stronger responses than those that have been continuously exposed. This is an example of which phenomenon?
a) synaptic scaling
what property of NDMA receptor makes it well suited to detect coincident presynaptic & postsynaptic activity?
NMDA receptors have a very high affinity for glutamate, so the transmitter remains bound to the receptor for many tens of milliseconds
what determines the strength of the synapse at the excitatory glutamatergic synapse?
strength of synapse is determined by a number of AMPA receptors at the time. LTP is associated with addition of new AMPA receptors to the synapse. LTD is associated with removal of AMPA receptors from synapse.
what is the mechanism underlying LTP at excitatory glutamatergic synapse?
1) neuronal activity induces glutamate release into synaptic cleft.
2) glutamate binds to both receptors AMPAR & NMDAR. however, initially Na flows only thru AMPAR bc NMDAR blocked by Mg
3) Postsynaptic depolarization removes Mg block & Ca2+ (& Na+) can flow thru NMDAR
4) resultant rise in Ca2+ level within dendritic spine is critical trigger for LTP
5) Ca2+ influx in dendritic spines activates intracellular signaling pathways such as CaMKII & molecular changes. molecular changes in postsynaptic neuron leads to change in synaptic strength (synaptic efficiency)
6) thus NDMA receptor mediated Ca2+ rise in postsynaptic dendrite is primary signal inducing synaptic plasticity
