Lecture 2: Synapse And Plasticity I

Question 1

Synapses

Answer 1

Highly specialized neuronal sites
Basic information processing units
Form neuronal circuits in the brain
Allow rapid information communication
Convert action potentials to neurotransmitters back to action potentials

Question 2

The 2 Parts synapses responsible for synaptic transmission

Answer 2

Pre synaptic terminal and postsynaptic apparatus

Question 3

Presynaptic terminal

Answer 3

active zone
synaptic vessels.
Converts action potential to neurotransmitter
Releases neurotransmitter

Question 4

Postsynaptic apparatus

Answer 4

Postsynaptic receptors
Density differs in nature
Receives neurotransmitters
Convert transmitter to action potential by ion flow

Question 5

Exocytosis (synaptic vessels)

Answer 5

1. Transmitter made and stored in vesicles
2. Action potential goes through presynaptic terminal
3. Presynaptic terminal depolarizes leading to voltage gated Ca2+ ion channels opening
4. Influx of Ca2+ into presynaptic terminal results in vesicles fusing with presynaptic membrane
5. Transmitters released into synaptic cleft by exocytosis
6. Transmitter binds to receptors of the postsynaptic membrane causing the opening and closing of postsynaptic channels
7. Postsynaptic current leads to excitatory or inhibitory potential that changes the cell excitability

Question 6

SNAREs complexes

Answer 6

They help with the fusion of vesicles to the presynaptic membrane. When the vesicle docks, complexes are formed to pull the membranes together. Ca2+ entering the cell binds to SYNAPTOTAGMIN, catalyzing membrane fusion.

Question 7

Postsynaptic transmitter receptors

Answer 7

Specific receptor proteins that open when bound to by transmitter

Question 8

2 Types of postsynaptic transmitter receptors

Answer 8

Transmitter gated ion channels (rapid)
G-protein coupled receptors (modulatory)

Question 9

Excitatory synaptic transmission

Inhibitory synaptic transmission

Answer 9

Increase probability of firing an action potential in a post synaptic neuron

Decrease probability of firing an action potential in a post synaptic neuron

Question 10

Inhibitory synaptic transmission

Interneurons

Answer 10

Control inhibitory synaptic transmission
Release inhibitory neurotransmitters (GABA & glycine)

Question 11

Inhibitory synapse transmission

GABA and glycine receptors are permeable to

Results in membrane potential hyperpolarisation by bringing the neuronal resting membrane potential away from threshold

Answer 11

Chloride ions

Chloride influx

Question 12

For excitatory synapses, the primary excitatory transmitter released from presynaptic terminal in the brain is

Answer 12

Glutamate

Question 13

3 main glutamate receptor subtypes

Answer 13

AMPA
NMDA
Metabotrophic glutamate receptors (mGluR)

Question 14

AMPA & NMDA postsynaptic receptors / (Ionotrophic type glutamate receptors )

Answer 14

Co-localized in postsynaptic membrane/ (activate neurons by conducting current)

Question 15

(-mGluR) / (metabotrophic glutamate receptors)

Answer 15

Activate neurons by second messenger pathways

Question 16

Difference of AMPA and NMDA receptors (ionotrophic glutamate receptors)
- permeability
- NMDA receptors

Answer 16

Both receptors are permeable to Na+ and K+ ions but NMDA is highly permeable to Ca++

NMDA receptor is voltage gated.

Question 17

NMDA receptors
- at resting membrane potential
- when postsynaptic membrane is depolarized

Answer 17

• magnesium blocked channel pore
• Mg2+ unbound and current flows through into neuron

Question 18

NMDA receptor
Why is pre and post synaptic activation needed?
What are they specifically (pre and post synaptic activation)?

Answer 18

Current to flow through into cell

Presynaptic terminal glutamate release and postsynaptic cell depolarization (‘coincidence detector’)

Question 19

Higher level of pre- and postsynaptic activation,

Answer 19

Higher the magnitude of calcium influx through NMDA receptor
- used as a measure for pre- and postsynaptic co-activation