Lecture 27- refinement of synaptic connections II Flashcards
What is the biological mechanism for strengthening and maintaining synapses?
-change in receptors in synapses
What are the four glutamate receptors?
-Four kinds, NMDA, AMPA, kainate and metabotropic
What do NMDA receptors pass?
-Ca2+, Na+, K+ ions
What do AMPA and kainate receptors pass?
- pass Na+ and K+ ions
What do metabotropic activate?
-activates second messengers
What does glutamat activate?
-Glutamate activates all of the four types of receptors, each can be differentiated by specific drugs that activate them
How do AMPA receptors work?
-ions just go through -Na+, K+
How do NMDA receptors work?
-Don’t work at resting membrane potential - Blocked by Mg++ ion -the Mg2+ must move= the membrane threshold needs to change -so AMPA change the membrane potential and unblock the NMDA then more ions go through -Ca2+, Na+, K+ go through
How do the metabotropic receptors work?
-they are modulatoric receptors, once activated, secondary messengers activated, phospholipase beta 1 is activated and then donstream effects

What are the silent synapses?
-Four kinds, NMDA, AMPA, kainate and metabotropic -Some structural synapses are silent (activation has no effect on target cell) - Many glutamatergic synapses have NMDA receptors only, no AMPA - Common in development
How does unmasking of silent synapses?
-Depolarizing cell displaces Mg++ ion from pore of NMDA receptor -NMDA receptor can now generate signal -Unmasks previously silent synapse -How does this happen? -Co-‐ordinated firing of neurons so that cell becomes sufficiently depolarised -Insertion of AMPA receptors -glutamate receptors: four kinds NMDA, AMPA, kainate and metabotropic -dynamic= changes depending on what the system needs
What are the concepts in Hebbian synapses?
- Donald Hebb proposed that competition depends on relative timing of activation of synapses
- Neurons that fire together, wire together
- neurons that fire together will always fire together, coordinated firing
- grow more terminals -need coordinated amount of synaptic activity

What are some details about Clive Wearing?
- severe amnesia -every single line is new, cannot remember more than 10 seconds -similar to HM except HM had the temporal lobe (including the hippocampus) taken out -Clive wearing had damage in the ability to strengthen synapses thus no long term memory forms
What are some details about H.M?
-Bilateral resection of medial structures of the temporal lobe, to treat severe epilepsy (Scoville and Milner, 1957) -Profound impairment of recent memory in absence of other intellectual loss (IQ of 112 post-‐surgery) -Could not remember what he had for breakfast, find his way around the hospital or recognize anyone he had met since the surgery
What did Brenda Milner discover?
-using H.M. as an experimental model discovered the way short term memory is converted to long term memory= refinement of synaptic connections!

What does the hippocampus do?
-stores memories
What is the experimental technique often used for exploring the temporal lobe?
- electrophysiology
- many conserved areas between mice and humans
- input into dentate gyrus and circles to CA1 and leaves to the cortex
- experimental technique= electrophys= activate the connection between CA3 and CA1 and see if these neurons fire and wire together

What is another way of using electrophysiology for research?
- measure how much activity from CA1 when activate CA3
- lot of activation
- LTP=then doesn’t go back to bseline, enhanced activity, will fire more readily later = as the assumption is that it will be needed

What is the long term potentiation?
A brief tetanic stimulation of one input results in increased size of subsequent EPSPs (excitatory post synaptic potential) in that input only.
What are short term changes with LTP?
- these changes are fast
- AMPA receptors are inserted into the postsynaptic membrane
- the postsynaptic neuron will fire more readily

What are the long term changes with LTP?
- if you give many more electircal stimulation= greater form of LTP= late LTP= this is governed by protein synthesis (know as when put in a protein inhibitor then the response disappears)
- electrophysiology= the technique
- have the brain slice in a bath

What is the Morris maze test?
-a way to examine memory in mice, tests their ability to tell where they are -but if have a disruption if pclbeta1 then cannot do it
What are the types of subunits in NMDA receptors?
- has 4 subunits
- NR1 ia always tehre and NR2A and NR2A interchange and change the confirmation of the receptor
- NR2B is more plastic (in babies)
- NR2A is less plastic

What happened in the mice with NMDA receptors knocked out?
-control search for the platform when your remove it= know it should be there -the NMDA receptor mutant doesn’t remember -didn’t have any NMDA receptor

