the synapse Flashcards
(25 cards)
What is the synapse?
A functional connection between neurones
What do synaptic knobs contain?
Vesicles containing neurotransmitters, lots of mitochondria, thickened membrane
What does the synaptic cleft separate?
The presynaptic membrane from the postsynaptic membrane
What are neurones containing acetylcholine called?
Cholinergic neurones
What causes the presynaptic membrane to depolarise?
Arrival of action potentials
What does this stimulate?
Calcium ion channels to open in the presynaptic membrane so calcium ions diffuse in
What does this cause to happen?
Vesicles containing acetylcholine to merge with the presynaptic membrane and break open
What happens to acetylcholine?
It diffuses across the synaptic cleft
What happens then?
Acetylcholine binds to specific protein receptor on postsynaptic membrane
What does this receptor stimulate?
Open of sodium ion channels leading to the depolarisation of postsynaptic membrane
What is the acetylcholine broken down by?
Acetyl cholinesterase
What is acetylcholine broken down into?
Acetyl and choline
What happens to the broken-down acetylcholine?
Taken up into the synaptic knob by active transport and is resynthesized (ATP needed)
Why is the synapse unidirectional?
Only presynaptic membrane has neurotransmitter, and only postsynaptic membrane has receptors for neurotransmitter
What is summation?
Additive effect of several impulses causing depolarisation of the postsynaptic membrane
What are the types of summation?
Spatial and temporal
What is spatial summation?
Where two or more impulses from different synaptic knobs arrive simultaneously at different regions on the same neurone
What is temporal summation?
Two or more impulses arrive in rapid succession at the same place
What is an inhibitory synapse?
A synapse that has inhibitory effects on the postsynaptic neurone
How is this usually achieved?
By the release of negative chloride ions or the removal of potassium ions which causes more negative charge inside the axon
Which neurotransmitter has this effect?
GABA
What will this cause?
It will make the threshold level of depolarisation harder to be achieved
How can drugs make transmission faster?
Similar structure of normal transmitter and have the same effect
How can drugs stop transmission?
Have a similar structure but do not produce the same effect and prevent normal neurotransmitter from entering OR they can prevent the release of a neurotransmitter
