Synapses and neurotransmitters Watch

youssef9461
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Hello,
I just need to know whether the binding of neurotransmitters to the receptors on the membrane of the post-synaptic neuron depolarizes it or prevents its depolarization. when the rod cells in the retina release glutamate, it prevents the depolarization of the bipolar cell but in the general neuron, neurotransmitter causes the cell to get depolarized. So, please anybody explain the difference.
Thanks a lot!!
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TheVirtualPhoton
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(Original post by youssef9461)
Hello,
I just need to know whether the binding of neurotransmitters to the receptors on the membrane of the post-synaptic neuron depolarizes it or prevents its depolarization. when the rod cells in the retina release glutamate, it prevents the depolarization of the bipolar cell but in the general neuron, neurotransmitter causes the cell to get depolarized. So, please anybody explain the difference.
Thanks a lot!!
Generally, binding of neurotransmitters to the post-synaptic neuron will depolarise it. This is true for all excitatory synapses.
There are different neurotransmitters, some are excitatory, some are inhibitory. Those that are inhibitory will prevent depolarisation of the post-synaptic neuron.
Retinal cells are special in that they signal through hyperpolarisation rather than depolarisation, but most signals are sent through excitatory synapses.
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youssef9461
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(Original post by TheVirtualPhoton)
Generally, binding of neurotransmitters to the post-synaptic neuron will depolarise it. This is true for all excitatory synapses.
There are different neurotransmitters, some are excitatory, some are inhibitory. Those that are inhibitory will prevent depolarisation of the post-synaptic neuron.
Retinal cells are special in that they signal through hyperpolarisation rather than depolarisation, but most signals are sent through excitatory synapses.
Thanks a lot!
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macpatgh-Sheldon
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TheVirtualPhoton, who I presume is an optometrist or photophysicist, has provided a good answer.

I would like to add one or two points to help OP out, especially if he/she is aiming for A*.

1. I believe there are almost equal numbers of excitatory and inhibitory neuronal synapses, particularly in the CNS, where multiple inputs by way of axo-axonic, axo-dendritic, axo-somatic and dendro-dentritic synapses are summated to create an effect that will be excitatory or inhibitory depending on the direction of the overall input; this is part of the mechanism of higher cerebral function.
2. Excitatory neurotransmitters include noradrenaline (NA) and acetylcholine (ACh), although the effects of these on some types of receptors can also be inhibitory e. g. the action of NA on pre-synaptic alpha-2 receptors (which comes in useful in medicine with a drug like yohimbine [an alpha-2 agonist [=stimulant]]).
3. Inhibitory neurotransmitters include GABA (gamma-aminobutyric acid) and some amino acids.
4. When an excitatory neurotransmitter acts on a post-synaptic receptor it causes depolarization to produce an EPSP [Excitatory Post-Synaptic Potential], while when an inhibitory neurotransmitter acts on its receptor, it generates a hyperpolarization or IPSP [Inhibitory Post-Synaptic Potential].
5. The vesicles carrying an excitatory neurotransmitter are usually spherical, while those carrying an inhibitory neurotransmitter are usually elongated.

I appreciate that this is beyond A level syllabus, but would impress any examiner in a synoptic essay Q.

Best of luck!

M (specialist biology tutor)
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