Chemical Synaptic Transmission Flashcards
Where does action potential arrive in a neuron?
The presynaptic membrane
Which channel opens when an action potential arrives at the presynaptic membrane?
Ca+ (Calcium channel)
What happens to the Ca+ channel when it is opened by the action potential?
- There is an influx of Ca+ ions
- localised depolarisation of the neuron
What is synaptotagmin & what does it do?
A protein in the vesicle membrane that sense local rise in Ca2+
What protein senses a local rise in Ca2+ ions when the channel opens?
synaptotagmin
Where is synaptotagmin found?
In the vesicle membrane
What causes the synaptic vesicles to fuse with the presynaptic membrane in the active zone?
rise in Ca2+ ions
Where does the synaptic vesicle fuse with the presynaptic membrane?
active zone
What proteins drive the fusion of the synaptic vesicle and presynaptic membrane?
SNAREs
What are v-SNAREs associated with
the vesicle
What are T-SNAREs associated with
the presynaptic target membrane
Where is the neurotransmitter released to?
the synaptic cleft / gap
What happens to neurotransmitter molecules in the synaptic gap?
They DIFFUSE across the gap and BIND to specific receptors on the post-synaptic membrane
Which neurons open the Na+ channels?
Excitatory neurons
What happens once the excitatory neurons open the Na+ channels
This causes and influx of Na+ into the dendrite
What happens when sufficient Na+ enters the dendrite?
depolarisation occurs resulting in action potential (this carries the chemical signals to the next neuron)
What are the 5 steps of action potential?
1) a stimulus (from sensory/ other neuron) causes target cell to depolarize toward the threshold potential
2) If threshold is reaches, all Na+ channels open and membrane depolarizes
3) At the peak of action potential, K+ channels open. K+ begins to leave cell. Na+ channels also close
4) membrane hyperpolarizes as K+ ions leave. Membrane enters a refractory period and cannot fire.
5) K+ channels close. Na+ and K+ transporter restores resting potential
What are the 3 major structural components of the chemical synapse?
- Presynaptic swelling of the axon
- postsynaptic element of recipient cell (dendrites)
- Synaptic gap
What are the 4 main steps of chemical synapse transmission?
- Arrival of an action potential at the presynaptic swelling (axon terminal)
- Depolarisation of the presynaptic membrane
- Release of neurotransmitters
- Neurotransmitters diffuse across the synaptic gap and bind rapidly to the post synaptic receptors on the dendrite
What is the function of a V-SNARE
mediate the process of exocytosis
What is the function of a T-SNARE
To form stable subcomplexes and guide V-snares
(Associated with the presynaptic target membrane)
