L6 - The Plastic Synapse

Question 1

What is the structure of the synapse?

Answer 1

pre-synaptic terminal

• machinery for making and concentrating transmitter in vesicles
• machinery for allow rapid fusion of vesicles

synaptic cleft
- essentially CSF

Postsynaptic membrane
- High concentration of membrane bound proteins that sense chemical transmission

Question 2

Describe synaptic transmission

Answer 2

Action potential invades the pre-synaptic terminal

The rseulting depolarisation open Ca2+ channels

Ca2+ binds to a sensor protein

transmitter filled vesicles are drawn to the pre-synaptic membrane where they fuse

Transmitter spills across the narrow cleft

transmitter bind post-synaptic receptors that open allowing ions to flow

Question 3

What are the two major neurotransmitters in the CNS

Answer 3

1. Excitatory = Glutamate

2. inhibitory: GABA

Question 4

What are the postsynaptic receptors for GABA?

Answer 4

GABA(a) receptors = Cl-

Question 5

What are the postsynaptic receptors for Glutamate?

Answer 5

AMPA receptors = NA+ (the workhorse)

NMDA = Ca+ (the communicator)

Question 6

What 3 synaptic properties define synaptic strength?

Answer 6

Number of synapses

Probability of release

Quantal size

Question 7

What properties do you need from synaptic plasticity if this is where memories are formed?

Answer 7

specificity

co-operativity - cells that wire together fire together)

Longevity (can be measured for years in vivo

Question 8

What is LTP?

Answer 8

long term potentiation

Trains of stimulation resulted in a long-lasting increase in synaptic strength. these were specific, co-operative and long-lasting

Question 9

which receptor and neurotransmitter is responsible for LTP?

Answer 9

postsynaptic Ca2+ through NMDA receptor

How does the NDMA receptor act as a coincidence detector?

Question 10

what goes wrong when trhe ability to remember is lost?

Answer 10

Synapses lose their ability to be plastic

• AD
• Down syndrome
• Age

Question 11

Why has there been show progress in understanding dementia and other neuro disorders?

Answer 11

Although synapses are critical to the formation of memory we are a long way from fully understanding how memories are formed

therefore it is difficult to fix

Question 12

What are the problems with studying the brain?

Answer 12

encased in a hard shell

the electric signal (AP) occurs very quickly

the brain is a series of connected neuronal networks – 100 billion neurons connected in trillions of possible ways

Question 13

What are the new ways to look at the brain?

Answer 13

MRI

Dense Arrays of electrodes measuring electrical activity - can record many places but still only clusters of neurons