Nervous system 6, Synapse

Nerve cells get so close, but never actually touch.There are very small gaps between individual nerve cells and between motor neurones and muscles. These gaps are called synaptic gaps. The gap is a physical space and the electrical nerve impulse is unable to jump across. The synapses are necessary to limit the propagation of an impulse around the nervous system. If all of the neurones were directly physically interconnected then any one nerve impulse would be propagated around the whole nervous system resulting in gross over- activity (this would probably result in continuous convulsions).
However, despite this need for electrical limitations, it is essential that nerve impulses can pass from one neurone to another when required. To allow this to happen the nerve fibre at one side of the synaptic gap releases a chemical called a chemical transmitter (neurotransmitter). This transmitter will then diffuse across the gap and generate a further electrical nervous impulse in the second neurone. Only the nerve fibre on one side of the synapse is able to secrete chemical transmitter. This means an impulse can travel from this first neurone to the second but not back in the other direction. The result is that synapses act as valves, only allowing one way transmission of impulses.
The neurone before the gap is termed the pre-synaptic neurone and the one after the gap as the post-synaptic neurone. Just before the gap, the pre-synaptic neurone widens out into a structure called the synaptic end bulb. This contains mitochondria to provide energy for the function of the synapse. The bulb also contains vesicles of chemical transmitter substances which have been previously synthesised by the neurone. When a nerve impulse arrives in the synaptic end bulb it causes some secretory vesicles to fuse with the pre-synaptic membrane releasing some chemical transmitter into the gap. After diffusing across the gap these transmitter molecules bind onto specific receptor sites on the post-synaptic membrane. Binding of transmitter into the receptor site activates the site. When enough of these receptor sites are activated by the chemical transmitter a further electrical impulse is generated in the post synaptic neurone.
If an impulse should arrive at the synapse via the post-synaptic neurone it will not be able to cross the gap and so will terminate. So, a nerve impulse is electrical when traveling along nerve fibres and chemical when traveling across a synaptic gap. A synapse may occur between two nerve fibres or between a nerve fibre and a cell body.
The connection between the synaptic end bulb of a motor neurone and a muscle is also via a synapse. Because this junction connects a nerve to a muscle it is referred to as a neuromuscular junction. As in a nerve to nerve connection, chemical transmitter is released, diffuses across the gap and binds onto specific receptor sites. When sufficient of the receptor sites are activated by the binding of transmitter, the muscle will be stimulated to contract. The surface of the muscle where the receptor sites are located is termed the motor end plate.

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As always very well explained thank you Dr. Campbell!!!

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I just watched your explanation. It's very helpful. Thanks. Profesor.

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You explained very well 👍

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[@murtadhaaljuboori8024]

I love your explanation and your voice as well

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Thank you for this video!

[@Amfkndinosaur]

10:55 "you think you are enjoying something.....really you are not. " idk why but that was funny. Great Lecture. WOW. I did enjoy it Dr. Campbell dont tell me otherwise. haha

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[@supriyashastri714]

Thank you sir. Your videos are very helpful.

[@liziepashane7799]

Can you explain about the reuptake or how the neurotransmitters are removed from synaptic

[@user-rm7tl8tv8b]

Thanks a lot for simplifying the nervous system

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your the best...thank you soo much 'you make my studies much easier

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Thank you!

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you have admired me so much

[@sharanaditya]

Wont the neurons run out of neurotransmitters after a period of time? Btw thanks for the video

[@Ninja55537]

Thank you so much ❤️

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Thank you so much for all these splendid lectures. “A learned guide should be a sheep, not a bird. A sheep gives its lamb milk, while a bird gives its chick regurgitated food.” I am studying anatomy physiology on the internet because of two professors. You and professor Fink. And the subject is sublime. Thank you so much.

[@Campbellteaching]

Thanks for this thoughtful reflection and feedback Arif.

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[@sofianbio4997]

That’s was very helpful thank you

[@mohammedanaskhan5772]

sir as we know impulse travels with the help of number of neurons ,now is the receptor part or post synaptic membrane a part of another dendrite (i.e neuron).

[@Campbellteaching]

+mohammed anas Khan Yes, the receptor sites are the start of the next neuron. No two neurons physically touch, the gap is crossed by chemical transmitters. So the transmitter molecules are released by the first neuron, and received by the next individual neuron.

[@srijalsrivastava5164]

Sir I love your teaching sir wish a Happy New new year

[@rachealokello6575]

Thanks a lot

[@dr.yuvarajanpalanisamy9805]

thank you sir ,wonderful explaination ,the transmitters you told serotonin,dopamine,glutamate,gaba are located in brain so these all about sensory neurons taking information from outside the CNS, but in dream we feel sorrow ,pleasure ,active without taking any stimulus from outside by neurons which means the brain itself can regulate which receptor to be released independent of external stimuli .,is it correct sir or am confused ?

[@Campbellteaching]

I guess it can be both. The brain can react to external stimulus, for example generating pleasure during eating or sex. However, mood can be determined by the physiology of the brain alone, as in depression or mania.

[@dr.yuvarajanpalanisamy9805]

@@Campbellteaching hence nervous system becomes complex to understand and treat it is both depending by stimulus and independent on its own by how we think...totally twisting rather in a standard formula like other systems Thank you for replying sir

[@suzyho2169]

What is the difference between synapse and synaptic cleft? Thank you so much

[@Lara-vc4gq]

suzy ho synapse is the link between the neurons whereas the synaptic cleft is the SPACE between them.

[@suzyho2169]

Thank you

[@ifeomammachukwu9727]

What's the difference between the link and space?am confused

[@Ninja55537]

@@ifeomammachukwu9727 link means connection and space is place

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*thx*

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Dr john Campbell sir rare knowledge is being imparted by you salute to you 24/07/2022

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[@darren1121]

My neurotransmitters find your joke amusing.

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