Synaptic Transmission

Question 1

overview of what happens

where can neurotransmitter synthesis take place? (2)

packaging? where?

what triggers the release?

where are vesicles stacked against? held by?

what releases them from axon?

what does it do next?

Neurotransmitter removal? (4)

Answer 1

Neurotransmitter synthesis (can happen in cell body or in axon terminal)

Neurotransmitter packaging (axon terminal use csm to create synpatic vesicles)

Neurotransmitter release is triggered by depolarization -AP arrival will cause VGCC to open so Ca2+ influx and the vesicles are stacked against the presynaptic membrane and they’re held in place by specialised proteins

Exocytosis - Ca2+ attaches to specialised proteins which trigger the vesicles to fuse with the membrane so it can release the neurotransmitter

Neurotransmitter binds selectively to postsynaptic receptors

Neurotransmitter removal

• > via enzyme degradation
• > diffusion
• > uptake into glia where it can be broken down and sent to terminal
• > re-uptaken and recycled

Question 2

Fast, time-dependent transmission

3 receptors? examples?

Answer 2

ligand-gated (ionotropic) receptors - signalling molecule to open channel e.e glutamate and GABA

Fast, time-dependent excitation e.g. glutamate in CNS,
acetylcholine @ NMJ -> Na+ into the cell so excitatory

Fast, time-dependent inhibition .g. g-aminobutyric acid (GABA), glycine -> Cl- into the cell so inhibitory

Question 3

Slow, non-time-dependent effects

what kind of receptors?

what is special about these?

Answer 3

metabotropic (modulatory) receptors
e.g. dopamine, acetylcholine, serotonin, noradrenaline

Has receptor but no channel. activates G-protein which acts as an intermediatory and second messenger therefore intracellular signalling