Q4: Neurotransmitters and Synapses Flashcards
Synapses transmit
Information
Where and how do synapses transmit information
From one neurone to another by means of chemicals called neurotransmitters
Synaptic cleft
Small gap which separates neurones.
Presynaptic neurone
Neurone that releases the neurotransmitter
Synaptic knob
A swollen portion at end the of the presynaptic neurone which the axon ends in.
What does the synaptic knob possess
And why
Many mitochondria and large amounts of endoplasmic reticulum.
Required in the manufacture of neurotransmitter which takes place in the axon?
Where does manufacturing of neurotransmitter occur
In the axon
Where is neurotransmitter stored?
Synaptic vesicles
What happens once the neurotransmitter is released from the synaptic vesicles?
It diffuses across to the post-synaptic neurone, which possesses very specific receptor proteins on its membrane to receive it.
Features of synapses
Unidirectionality
Summation
Unidirectionality
Synapses can only pass information in one direction- from the presynaptic neurone to the post synaptic neurone, in this way they act like valves.
Two types of summation
Spatial
Temporal
Summation
Rapid build up of neurotransmitter in the synapse to trigger an action potential.
Spatial summation
A number of different presynaptic neurones together release enough neurotransmitter to exceed the postsynaptic neurone’s threshold value.
Together they trigger a new action potential.
Temporal summation
A single presynaptic neurone releases neurotransmitter many times over a very short period.
How is a new action potential generated at a postsynaptic neurone?
The concentration of neurotransmitter exceeds the threshold value of the postsynaptic neurone.
Inhibitory synapses
Synapses that make it less likely that a new action potential will be created on the postsynaptic neurone.
Synapses act as
junctions
A single impulse along one neurone can ….. at a synapse
initiate new impulses in a number of different neurones at a synapse.
Allowing a single stimulus to create a number of simultaneous responses.
A number of impulses ….. at a synapse
can be combined at a synapse.
This allows impulses reacting to different stimuli to contribute to a single response.
Cholinergic synapse
A synapse whose neurotransmitter is acetylcholine.
Acetylcholine
made up of?
made up of acetyl (ethanoic acid)
and choline
Where are cholinergic synapses found?
in vertebrates
in the central nervous system
at neuromuscular junctions
Neuromuscular junctions
junctions between neurones and muscles
Which enzyme hydrolyses acetylcholine?
acetylcholinesterase
What causes sodium ion protein channels to open?
binding of acetylcholine to receptor sites on sodium ion protein channels in the membrane of the postsynaptic neurone
What causes calcium ion protein channels to open?
the arrival of an action potential at the end of the presynaptic neurone
How do calcium ions enter the synaptic knob?
facilitated diffusion
What generates a new action potential in the postsynaptic neurone?
influx of sodium ions
What is ATP from mitochondria used for in the presynaptic neurone?
recombining acetyl and choline to form acetylcholine
