Synaptic Transmission Flashcards
What initiates vesicle exocytosis?
An action potential arrives at the end of a synapse which opens calcium ion voltage gated channels and causes an influx on calcium ions into the pre-synaptic membrane (down their electrochemical gradient). This results in vesicles containing neurotransmitters being released from the pre-synaptic membrane by exocytosis.
What is the difference between the 2 types of receptor on the post-synaptic membrane?
Ligand gated ion channel- fast depolarisation of the membrane (fast synaptic transmission)- e.g. acetylcholine at a neuromuscular junction
G protein linked receptor- slower in onset and last much longer as a multiple step reaction of phosphorylation’s must occur intracellular before depolarisation of the membrane will occur. This is a slow synaptic transmission. For example, noradrenaline binding to alpha receptors in peripheral blood vessels.
What do vesicles travel along within the pre-synaptic knob?
A specialised microtubule network.
How do vesicles know where to go on the pre-synaptic membrane?
Receptors on the surface of the vesicles and on the surface of the pre-synaptic membrane bind together and signal to the vesicle that they should release their contents by exocytosis at this particular point on the membrane
On the pre-synaptic membrane, what is homotropic inhibition
This is where the release of a neurotransmitter inhibits itself by binding to presynaptic auto receptors on the presynaptic membrane to decrease the release of this type of neurotransmitter
What is heterotropic inhibition?
Where a pre-synaptic knob has axon terminal endings close to the end of another pre-synaptic membrane and when neurotransmitter is released, it acts as an inhibitor for the release of the neurotransmitter at the other synapse (e.g. sympathetic nervous system acting as an inhibitor on the parasympathetic nervous system)
What is Co-transmission?
The release of multiple neurotransmitters from different synaptic vesicles (which vesicles are released depends on their sensitivity to calcium ions)
What is Co-release?
This is where different types of neurotransmitter are in the same vesicle and are therefore released from the same vesicle upon arrival of an action potential at the axon terminal.
