Synaptic Transmission

Question 1

What are post-synaptic potentials?

Answer 1

PSPs are created through opening up channels into neurone synapse.

Opening up Na+ and Ca2+ channels create EXCITATORY PSPs.
Opening up K+ and Cl- channels create INHIBITORY PSPs.

EPSPs and IPSPs are summed to decide whether the neurone generates an AP. (exceed -55mV).

Question 2

How do SNAREs mediate vesicle fusion?

Answer 2

v-SNAREs on vesicle and t-SNAREs on target membrane partially assemble.

Full assembly is blocked by complexin. Need Ca2+ to binds to synaptotagmin to displace complexin.

Question 3

Describe how Ca2+ and synaptotagmin function to mediate neurotransmitter release.

Answer 3

Complexin blocks the assembly of SNAREs to release NTs.

1. Action potential arrives, depolarisation the presynapse.
2. Voltage gated Ca2+ channels open
3. Ca2+ binds to synaptotagmin, which then displaces complexin, allowing neutrotransmitters to be released.

Question 4

Describe the two dominant CNS neurotransmitters.

Answer 4

Glutamate:

• Excitatory NT
• Binds ionotropic receptors (iGluRs)
• Na+ and Ca2+ channels.

GABA:

• Inhibitory NT
• Binds GABARs
• Cl- channels

Question 5

Describe the two main PNS neurotransmitters

Answer 5

Acetylcholine:

• Excitatory (through nicotinic - ionotropic, Na+ channels)
• Inhibitory (through muscarinic - metabotropic, enzyme activation)

Noradrenaline:

• Acts on alpha and beta adrenergic receptors.
• All are metabotropic, and can be excitatory or inhibitory.