Synaptic Plasticity

Question 1

Santiago ramón y Cajal (1894) stated

Answer 1

memories might be formed by strengthening connections between neurons

Question 2

Hebbs law =

Answer 2

when axon A is near enough to excite cell B and repeatedly takes part in firing it - some growth process or metabolic change takes place in one or both cells
A efficiency as one of the cells firing B is increased

Question 3

when A and B fire AP at the same time

Answer 3

the connection / synapse between them becomes stronger

Question 4

synaptic plasticity

Answer 4

The strength of synaptic communication between 2 neurons is not fixed
change in the strength of synaptic communications

Question 5

how was long term potentiation first studied

Answer 5

recordings of fEPSP in performant pathway of rabbits
insert stimulating electrode into pathway
eject dendrite gyrus of hippocampus into dendritic field
record synaptic responses
experiments - change amplitude vs control

Question 6

experiment to test hebbs law

Answer 6

evoke activity in A using stimulating electrode
see response in B
depolarisation of membrane potential to generate postsynaptic potential

Question 7

general properties of LTP

Answer 7

input specificity
associativity
cooperatively
persistence

Question 8

what is input specificity

Answer 8

LTP is induced selectively at a synapse or group of synapses that are formed between pre and post synaptic neuron
simultaneous activation of A and B - synapse between A and B is activated then this synapse will undergo LTP

Question 9

what is associativity

Answer 9

a weak stimulus in one pathway is not sufficient to elicit LTP
when paired with activity in another strong pathway = LTP in both pathways

Question 10

example of associativity (LTP)

Answer 10

A = weak
C = strong
if activity is just in A = B is not potentiated
is activity in A and C simultaneously = activity is elicited in B = both of the synaptic pathways undergo LTP

Question 11

cooperatively if LTP

Answer 11

a weak stimulus in one pathway is not sufficient to elect LTP
when paired with another (does not have to be strong) pathway = LTP in both pathways

Question 12

different between associativity and cooperatively

Answer 12

similar to associativity but does not require the second pathway to have a strong stimulus = just several input pathway activated at the same time

Question 13

persistence LTP

Answer 13

increase in synaptic strength will last across time
after LTP occurred the AP is A will be more likely to drive an AP in its postsynaptic partner B

Question 14

what is LTP induced by

Answer 14

high frequency conditioning stimulation

Question 15

what receptors are required for LTP at a synapse

Answer 15

NMDA

Question 16

why are NMDA receptors coincidence detectors

Answer 16

they detect presynaptic activity / glutamate
detect postsynaptic activity / depolarisation too

Question 17

when are NMDA receptors activated

Answer 17

depolarised potentials

Question 18

how are NMDA receptors blocked at polarised potentials

Answer 18

NMDA receptors
hyperpolarised/polarised potentials
magnesium ion blocks channel pore
prevents other ions moving across

Question 19

when glutamate binds to NMDA receptors

Answer 19

glutamate binds
magnesium ion block is removed
so now with glutamate ions can pads through channel pore into post synaptic cell

Question 20

what is needed to get LTP in NMDA receptors

Answer 20

Glutamate and depolarisation at the same time
= LTP

Question 21

why does NMDA receptors activation lead to LTP

Answer 21

allow calcium to enter
influence In facilitating LTPs

Question 22

why can’t AMPA activation lead to LTP

Answer 22

AMPA = allows movement of sodium ions
not calcium ions

Question 23

experiment of calcium on LTP

Answer 23

CA3 to CA1 synapses in hippocampus brain slices
EPSP
number of cells filled with calcium chelator (nitr5)
high frequency stimulus
cells filled with nitr5 = take up calcium - can’t undergo LYP
shows calcium is essential for LTP

Question 24

calcium effect on LTP

Answer 24

binding of calcium to calmodulin to CaMKII enzymes
causes a conformational change
active sites of the enzyme are released
able to go and act on downstream effectors

Question 25

what intracellular signalling cascades does calcium activate

Answer 25

ca2+/calmodulin kinase
protein kinase C
calpaan
G protein
adenylyl cycles

Question 26

what are the mechanisms by which LTP is expressed

Answer 26

• change in release properties (presynaptic)
• change in AMPAR properties (postsynaptic)
  *chnage in AMPAR numbers (postsynaptic)
  *synaptic growth (pre or post)

Question 27

what requires LTP to be induced in CA3 to CA1 synapses in hippocampus

Answer 27

Presynaptic glutamate release
Depolarisation of postsynaptic cell
Removal of the mg2+ block from NMDA receptors

Question 28

Long term depression

Answer 28

prolonged low frequency stimulation

Question 29

what do some forms of LTD depend on

Answer 29

NMDA receptor activation and Calum postsynaptic entry

Question 30

what can block LTD

Answer 30

intracellular calcium chelation using BAPTA

Question 31

LTD can be induced by

Answer 31

Activation of metabotropic glutamate receptors
activation of muscarinic ACh receptors

Question 32

3 processes involved in memory

Answer 32

encoding
consolidation
recall

Question 33

how do neuronal networks remember things

Answer 33

plasticity = enable strengthening of connections = information is now embedded in connectivity between the neurons involved in coding the stimulus
when the input is reactivated by a stimulus the activity is Abel to drive the reactivation of neurons with the network =beacuse of increase strength of connectivity

Question 34

too much LTP leads to

Answer 34

epilepsy

Question 35

too much LTP leads to

Answer 35

epilepsy

Question 36

LTP or LDP

Answer 36

HSF = NMDA receptor activation = LTP
LFS = NMDA receptor activation, MGLuR activation, mACh activation = LTD

different patterns of synaptic and NMDA receptor activation leads to different outcomes = LTP or LPD