JacobBob
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Can someone please explain temporal and spacial summation to me ?
I watched videos, I read my book, I read another book, I read stuff on the internet, I still have so many questions.

Maybe to start I should know this: Is there such a thing as an excitatory/inhibitory neurotransmitter? Or does depend on the synapse ?
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AH101
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You can get an excitatory or inhibitory synapse. An excitatory synapse is your normal synapse where the neurotransmitter causes sodium ion channels to open and allows depolarisation to occur allowing an action potential to be generated. An inhibitory synapse causes chloride ion channels to open instead and as chloride ions are negative it means more sodium ions would be required than normal to allow an action potential to be generated therefore it would be more difficult for an action potential to be stimulated in the post synaptic neurone (thus inhibitory)

Spatial summation is when many pre synaptic neurones are connected to a post synaptic neurone (as spatial basically means there is a lot of synapses in the 'space' )whereas temporal is when there is one pre synaptic neurone connected to one post synaptic but it is just the frequency of action potentials that changes (as temporal means time, there is more action potentials in a given amount of time)
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JacobBob
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(Original post by AH101)
You can get an excitatory or inhibitory synapse. An excitatory synapse is your normal synapse where the neurotransmitter causes sodium ion channels to open and allows depolarisation to occur allowing an action potential to be generated. An inhibitory synapse causes chloride ion channels to open instead and as chloride ions are negative it means more sodium ions would be required than normal to allow an action potential to be generated therefore it would be more difficult for an action potential to be stimulated in the post synaptic neurone (thus inhibitory)

Spatial summation is when many pre synaptic neurones are connected to a post synaptic neurone (as spatial basically means there is a lot of synapses in the 'space' )whereas temporal is when there is one pre synaptic neurone connected to one post synaptic but it is just the frequency of action potentials that changes (as temporal means time, there is more action potentials in a given amount of time)
What determines whether a synapse is excitatory or inhibitory ? Is it the post synaptic neurone ?
I read that if there were more than 1 pre synapse, whether an action potential is fired or not depends on the summation effect of all the presynapses ? Or sth along those lines

Is that correct ? Also what does that mean ?
I'm self teaching myself everything and I honestly don't understand anything .
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AH101
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It's determined by the receptor the neurotransmitter binds to and which ion channel it causes to open. Well from what ive learnt an inhibitory synapse causes chloride ion channels to open and the excitatory synapse causes sodium ions.
Yes it does depend on the summation effect. This is due to the all or nothing principle. If the action potential stimulated is not above the threshold, then there is no action potential (no matter how below it it is) and if it is above then the action potential is stimulated. Action potentials are all the same strength therefore this where the summation effect omes into play. The summation effect allows action potentials to meet that threshold so that an action potential can be stimulated in the next neurone. (This is what AQA says)
What determines whether a synapse is excitatory or inhibitory ? Is it the post synaptic neurone ?
I read that if there were more than 1 pre synapse, whether an action potential is fired or not depends on the summation effect of all the presynapses ? Or sth along those lines

Is that correct ? Also what does that mean ?
I'm self teaching myself everything and I honestly don't understand anything .
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JacobBob
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(Original post by AH101)
It's determined by the receptor the neurotransmitter binds to and which ion channel it causes to open. Well from what ive learnt an inhibitory synapse causes chloride ion channels to open and the excitatory synapse causes sodium ions.
Yes it does depend on the summation effect. This is due to the all or nothing principle. If the action potential stimulated is not above the threshold, then there is no action potential (no matter how below it it is) and if it is above then the action potential is stimulated. Action potentials are all the same strength therefore this where the summation effect omes into play. The summation effect allows action potentials to meet that threshold so that an action potential can be stimulated in the next neurone. (This is what AQA says)
Okay so in spatial summation could some of the synapses cause the Cl- ion channels to open and others cause Na+ ion channels to open ?
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AH101
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The point of summation is to allow the the action potential to reach the threshold so a new action potential can be stimulated. So in spatial summation the synapses are going to all open sodium ion channels as you want to meet the threshold, there would be no point for chloride ion channels to open as that would make your job harder to do.

(If you're AQA you don't really need to know it in this much detail so I don't really know this in that much detail)
(Original post by JacobBob)
Okay so in spatial summation could some of the synapses cause the Cl- ion channels to open and others cause Na+ ion channels to open ?
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