Long term potentiaiton

Question 1

Define Hebbian’s synapses

Answer 1

Co-ordinated activity in a pre synaptic terminal with a post synaptic neuron strengthens the synaptic connections between them

Question 2

What is the neuronal path of the hippocampus

Answer 2

Perforant path - Entorhinal cortex to the dentate gyrus
Dentate gyrus to the CA3 neurons - mossy fibres
Ca3 to Ca1 neurons - Schaffer’s collaterals Output via fornix/subiculum

Question 3

What is co-operativity

Answer 3

Enough synapses must be active simultaneously to cause significant special summation of EPSPs - not dependent on a high frequency of stimulus

Question 4

What is tetanus

Answer 4

High frequency stimulation producing a long lasting potentiation post synaptically

Question 5

What is the cellular mechanism of LTP

Answer 5

Sufficient depolarization of the post synaptic membrane will cause NMDA receptors to lose their Mg block - as a result Calcium is able to move into the post synaptic neuron and its increasing intracellular concentration take effect -
Calcium binds calmodulin kinase II
This phosphorylates itself to become more active
Also phosphorylates AMPA receptors making them more active
In response to CamKII activity - AMPA receptors in vesicles are transported to the post synaptic membrane and fuse - Increased receptor pool - Swelling of dendrites

Question 6

What relevance does LTP have in learning

Answer 6

Inhibition of LTP inhibits some forms of learning
Mouse water maze - if CamKII, NMDARs and cAMP pathways are inhibited - the mouse takes longer to find the platform
Drugs to enhance memory (nootropins) enhance LTP
Only necessary for some memory - not sufficient

Question 7

How do different parts of the hippocampus exhibit different types of LTP

Answer 7

Mossy fibre - CA3 neurons - mainly presynaptic - increased calcium release (cAMP mediated)
perforant path - dentate gyrus neurons don’t use CamKII