Synapses structure, function and transmission Flashcards
What does the unidirectionality of a synapse mean?
Synapses can only pass information in one direction
What is spatial summation
Number of different presynaptic neurones together release enough transmitters to exceed threshold value
What is temporal summation
A single pre synaptic neurone releases neurotransmitter many times over a short period to reach threshold value.
Purpose of an inhibitory synapse
Make it less likely that a new action potential will be created on the post synaptic neurone
How do inhibitory synapses work?
Presynaptic neurone releases neurotransmitter that binds to chloride channels in post synaptic membrane
Causes channels to open
Cl- move into post synaptic via facilitated diffusion
Binding of neurotransmitter causes opening of nearby K+ channels
K+ moves out of postsynaptic neurone into the synapse
Combined effect of chloride ions moving in and K+ moving out causes inside to be more negative and outside positive
Result hyperpolarisation
What are synapses that produce new action potentials called?
Excitatory synapses
What do cholinergic synapses contain?
Acetylcholine
Process of transmission across a synapse
Action potential arrives at presynaptic neurone, causing Ca2+ channels to open
Ca2+ moves in by facilitated diffusion
Influx of calcium ions causes synaptic vesicles to fuse with presynaptic membrane, releasing acetylcholine synaptic cleft
Acetylcholine diffuses across cleft and binds with receptor sites on sodium cannels, causing them to open
This causes influx of Na+ by facilitated diffusion
This cause’s depolarisation and generates a new action potential
How is acetylcholine reformed after generation of an action potential?
Acetylcholinesterase hydrolyses acetylcholine into an acetyl and choline group in order to disconnect rom the protein and prevent new action potentials.
Acetyl and choline diffuse back into presynaptic neurone
ATP is used to recombine into acetylcholine
