3f

Question 1

Synapse

Answer 1

Junction between axon terminals from a pre-synaptic neuron and the dendrites from a
post-synaptic neuron.

Question 2

Chemical synapse

Answer 2

Components
- Pre-synaptic neuron
- Axon terminal
- Synaptic cleft
- Post-synaptic neuron
- Dendrites, cell body
Synaptic knob: Location of the synaptic vesicles that contain the neurotransmitters
(act as ‘chemical messengers’).

Question 3

chemical process

Answer 3

1) Neurotransmitters are stored in small synaptic vesicles encased in lipid bilayer membranes. Prior to
activation, these vesicles are stored in the region of the synaptic knob (‘Active zones’).
2) Neurotransmitter release is initiated when an action potential
reaches the pre-synaptic axon terminal.
=> Opens Calcium voltage-gated channels on the synaptic knob
region
=> Calcium influx triggers the fusion of synaptic vesicles to the
pre-synaptic docking site and the release of NT by exocytosis.

Before calcium activation, synaptic vesicles are loosely docked to the active zones of the docking site by
the interaction of SNARE proteins anchored in both the vesicle membrane and axon terminal
membrane.
SNAREs = Soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors.
Calcium binds to a specific protein = Synaptotagmin
=> Changes the conformation of SNAREs (‘hold arms together’)
=> Membrane fusion and neurotransmitter release.