Synapse: Difference between revisions
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The synapse is a | The synapse is a specific site where neuronal signals are transmitted from cell to cell. It is a structure where the electrical signals of one [[Neuron|neuron]] are converted to chemical signals in order to transmit information from one [[Nerve cell|nerve cell]] to the next [[Nerve cell|nerve cell]](s). Postsynaptic cells are separated from presynaptic cells by a synaptic cleft. The electrical potential in the presynaptic cell changes which causes the cell to release a neurotransmitter signalling molecule by exocytosis. The neurotransmitter moves across the synaptic cleft and triggers an electrical change in the postsynaptic cell<ref>Bruce, A, Johnson, A, Lewis, J, Raff, M, Roberts, K and Walter, P (2008). Molecular Biology of the Cell. Fifth Edition. New York: Garland Science, Taylor and Francis Group, LLC. p682.</ref>.<br> | ||
A chemical synapse is the distinguishable gap (between 15-200nm wide)<ref>http://michaeldmann.net/mann13.html</ref> between the axon terminal of one [[Neurone|neuron]] cell and the [[Dendrites|dendrites]] of another. Electrical signals are able to continue across a chemical synapse due to the activity of [[Neurotransmitter|neurotransmitters]]<ref>http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php</ref>. Neurotransmitters are chemicals such as acetylcholine or [[Dopamine|dopamine]]. | |||
An electrical synapse is a physical connection between two [[Neurone cell|neurones]] and electrical signals are able to pass straight through from one neurone to the other without the help of neurotrasmitters<ref>http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php</ref>. | |||
=== What happens at the Cholinergic Synapse? === | === What happens at the Cholinergic Synapse? === | ||
Transmisson of an action potential across a synapse commonly involves [[Acetylcholine|Acetylcholine (Ach)]], a common neurocrine, neurones which secrete Ach are cholinergic | Transmisson of an action potential across a synapse commonly involves [[Acetylcholine|Acetylcholine (Ach)]], a common neurocrine, neurones which secrete Ach are cholinergic<ref>Silverthorn. D.U., 2007. Human Physiology an Integrated Approach. 4th Edition. San Francisco: Pearson Education Inc.</ref>. | ||
*An action potential arrives at the pre-synaptic membrane causing voltage-gated [[Ca2+ pump|Ca]]<sup>[[Ca2+ pump|2+]] </sup>[[Ion channel|ion channels]] to open. Ca<sup>2+</sup> moves in through the [[Pre-synaptic memebrane|pre-synaptic memebrane]], down the chemical gradient. <br> | *An action potential arrives at the pre-synaptic membrane causing voltage-gated [[Ca2+ pump|Ca]]<sup>[[Ca2+ pump|2+]] </sup>[[Ion channel|ion channels]] to open. Ca<sup>2+</sup> moves in through the [[Pre-synaptic memebrane|pre-synaptic memebrane]], down the chemical gradient. <br> | ||
*This influx of Ca<sup>2+</sup> results in vesicles containing Ach to fuse with the pre-synaptic membrane, Ach is released into the synaptic cleft by [[Exocytosis|exocytosis]]. | *This influx of Ca<sup>2+</sup> results in vesicles containing Ach to fuse with the pre-synaptic membrane, Ach is released into the synaptic cleft by [[Exocytosis|exocytosis]]. | ||
*Ach diffuses across the synaptic cleft and binds to specific neuroreceptor sites on the post-synaptic membrane. | *Ach diffuses across the synaptic cleft and binds to specific neuroreceptor sites on the post-synaptic membrane. | ||
*Binding of Ach opens Na<sup>+</sup> ion channels on the [[Post-synaptic membrane|post-synaptic membrane]]. Na<sup>+</sup> ions diffuse across the post synaptic membrane into the post-synaptic neurone (down the chemical gradient). This causes depolarisation of the membrane which in-turn initiates an [[Action potential|action potential]]. | *Binding of Ach opens Na<sup>+</sup> ion channels on the [[Post-synaptic membrane|post-synaptic membrane]]. Na<sup>+</sup> ions diffuse across the post synaptic membrane into the post-synaptic neurone (down the chemical gradient). This causes depolarisation of the membrane which in-turn initiates an [[Action potential|action potential]]. | ||
*The [[Enzyme|enzyme]] [[Acetylcholinesterase|acetylcholinesterase]] rapidly breaks down Ach in the [[Synaptic cleft|synaptic cleft]] (into [[Choline|choline]] and [[Acetyl-CoA|acetyl CoA]]) and the choline is transported back into the axon terminal where more Ach is synthesised | *The [[Enzyme|enzyme]] [[Acetylcholinesterase|acetylcholinesterase]] rapidly breaks down Ach in the [[Synaptic cleft|synaptic cleft]] (into [[Choline|choline]] and [[Acetyl-CoA|acetyl CoA]]) and the choline is transported back into the axon terminal where more Ach is synthesised<ref>Silverthorn. D.U., 2007. Human Physiology an Integrated Approach. 4th Edition. San Francisco: Pearson Education Inc.</ref>. <br> | ||
=== References === | === References === | ||
<references /> | <references /> | ||
Latest revision as of 20:33, 28 November 2016
The synapse is a specific site where neuronal signals are transmitted from cell to cell. It is a structure where the electrical signals of one neuron are converted to chemical signals in order to transmit information from one nerve cell to the next nerve cell(s). Postsynaptic cells are separated from presynaptic cells by a synaptic cleft. The electrical potential in the presynaptic cell changes which causes the cell to release a neurotransmitter signalling molecule by exocytosis. The neurotransmitter moves across the synaptic cleft and triggers an electrical change in the postsynaptic cell[1].
A chemical synapse is the distinguishable gap (between 15-200nm wide)[2] between the axon terminal of one neuron cell and the dendrites of another. Electrical signals are able to continue across a chemical synapse due to the activity of neurotransmitters[3]. Neurotransmitters are chemicals such as acetylcholine or dopamine.
An electrical synapse is a physical connection between two neurones and electrical signals are able to pass straight through from one neurone to the other without the help of neurotrasmitters[4].
What happens at the Cholinergic Synapse?
Transmisson of an action potential across a synapse commonly involves Acetylcholine (Ach), a common neurocrine, neurones which secrete Ach are cholinergic[5].
- An action potential arrives at the pre-synaptic membrane causing voltage-gated Ca2+ ion channels to open. Ca2+ moves in through the pre-synaptic memebrane, down the chemical gradient.
- This influx of Ca2+ results in vesicles containing Ach to fuse with the pre-synaptic membrane, Ach is released into the synaptic cleft by exocytosis.
- Ach diffuses across the synaptic cleft and binds to specific neuroreceptor sites on the post-synaptic membrane.
- Binding of Ach opens Na+ ion channels on the post-synaptic membrane. Na+ ions diffuse across the post synaptic membrane into the post-synaptic neurone (down the chemical gradient). This causes depolarisation of the membrane which in-turn initiates an action potential.
- The enzyme acetylcholinesterase rapidly breaks down Ach in the synaptic cleft (into choline and acetyl CoA) and the choline is transported back into the axon terminal where more Ach is synthesised[6].
References
- ↑ Bruce, A, Johnson, A, Lewis, J, Raff, M, Roberts, K and Walter, P (2008). Molecular Biology of the Cell. Fifth Edition. New York: Garland Science, Taylor and Francis Group, LLC. p682.
- ↑ http://michaeldmann.net/mann13.html
- ↑ http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php
- ↑ http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php
- ↑ Silverthorn. D.U., 2007. Human Physiology an Integrated Approach. 4th Edition. San Francisco: Pearson Education Inc.
- ↑ Silverthorn. D.U., 2007. Human Physiology an Integrated Approach. 4th Edition. San Francisco: Pearson Education Inc.