Week 3 Review

Question 1

Tetanic Stimulation

Answer 1

high frequency repetitive stimulation

Question 2

the strength of the synapse is referred to as

Answer 2

synaptic efficiency or synaptic weights

Question 3

LTP

Answer 3

long term potentiation: form of synaptic strengthening (potentiation) observed after tetanic stimulation & lasts for many minutes, hours, even days

Question 4

LTD

Answer 4

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

Question 5

NMDA-type glutamate receptor

Answer 5

ionotropic type of glutamate receptor that, can be opened by glutamate only when postsynaptic cell is depolarized well above resting potential (-70mV)

Question 6

magnesium block

Answer 6

near neuron’s resting potential, the ion-conducting pore of the NMDA receptor tends to be blocked by magnesium ions

Question 7

Hebb’s rule

Answer 7

idea that synapses are strengthened only when their (presynaptic) activity coincides with postsynaptic activation (depolarization); as a result “neurons that fire together, wire together”

Question 8

AMPA receptor

Answer 8

ionotropic type of glutamate receptor that can be opened by glutamate when postsynaptic cell is near its resting potential

Question 9

which of the following is a special feature of the NMDA glutamate receptor?

Answer 9

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

Question 10

which of the following is thought to play a role in LTP?

Answer 10

a) glutamate receptors

b) CaMKII

c) calcium

answer: all are correct

Question 11

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?

Answer 11

b) 1 & 3

Question 12

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?

Answer 12

b) only synapse 1 would be strengthened (synapse between neurons A & D)

Question 13

Hebbian learning can be described by the phrase; “neurons that fire together, wire together” which means?

Answer 13

b) synaptic connections are strengthened by neuronal activity

Question 14

Synaptic scaling is a phenomenon where

Answer 14

a) neurons adjust their sensitivity to stimuli dependent on their activity

Question 15

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?

Answer 15

a) synaptic scaling

Question 16

what property of NDMA receptor makes it well suited to detect coincident presynaptic & postsynaptic activity?

Answer 16

NMDA receptors have a very high affinity for glutamate, so the transmitter remains bound to the receptor for many tens of milliseconds

Question 17

what determines the strength of the synapse at the excitatory glutamatergic synapse?

Answer 17

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.

Question 18

what is the mechanism underlying LTP at excitatory glutamatergic synapse?

Answer 18

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