Nervous system 4, Nerve impulses

We have already mentioned that a nerve impulse is electrical. This electrical charge is generated by the relative distribution of ions on both sides of the cell membrane. If there are more negative ions inside the cell with relatively more positive ions outside, the overall charge will also be negative on the inside and positive on the outside. This state is sometimes referred to as the resting potential. This is the electrical condition a nerve fibre will be in when there is no nerve impulse passing a particular point. Because in this situation there is a negative pole inside and a positive pole on the outside, the cell is described as being polarized. These are the same as the poles of a battery, one of which is negative and the other positive.
However, when a nerve impulse is passing a point on a nerve fibre, the polarity across the cell membrane reverses. There is a change in the permeability of the membrane surrounding the nerve fibre. This allows ions to pass through the cell membrane leading to a change in the relative distribution of positive and negative ions on the two sides of the membrane. The result is the inside becomes positive and the outside negative. This reversal of polarity is referred to as depolarization. After the nerve impulse has passed, the polarity reverts back to being negative inside and positive outside. The process by which resting polarity is restored is termed repolarization. From this it can be seen that a nerve impulse is a wave of depolarisation which passes along a nerve fibre. It is this electrical wave which constitutes the nerve impulse. Changes in polarity necessary for the propagation of the impulse are brought about by changes in the relative distribution and concentration of ions. These concentrations may change because ions are able to pass through the cell membrane in specialised small gaps called ion channels.

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I suggest you to add some lectures about disease too ..

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May God bless!!!!

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I really can't believe how I struggle to go through the words in books ...but Dr Campbell you've simplified everything and I haven't even struggled to understand..thank you so much...

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Kind, considerate, thorough and respectful - thank you Dr. John

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I'm not a fan of watching videos for understanding, but after trying to understand the transmission through axon and it was futile, I came online. My instinct just clicked on Dr. John's channel. Goodness! I enjoyed this and I'm coming for more. I already did subscribed 😂❤

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Much love from Kenya 💕

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Thank you for explaining action potential!😊

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Thank you !!!!!

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I found this the hardest concept to understand so far! but grateful as always for your videos

[@amirzendehdel8876]

Thank you Dr Campbel , you made me better view to nerve's signal transmitting. :)

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Thank you prof
I never before understood this so well
Reminds me of studying in England and the detailed attention to content 😌

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Best video on nerve impulses I've ever seen !!! Thank you soooooooo much:)

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thanks for well explained on nerve impulses again thanks for clear the topic how to travel nerve impulses on human body

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Thanks dr john Campbell sir for imparting this vital and important knowledge 15/07/2022

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BEST EXPLANATION.

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Thank you DOCTOR

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India

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❤❤❤

So for example cold and heat sensors have different frequencies and when they combine they result in frequency of pain?

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Genius

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@11:00 who made Frequency coding of Adam and human beings at such a specialized coded system

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Outclassed

[@ottoraabbscee4739]

Dr. Campbell, thank you for your lectures here.
Question: what is the difference between a pressure transducer in the skin & a touch transducer in the skin, transducer of course being an entity changing a physical phenomena to an electrical or chemical signal. Thank you for your input/thoughts.
~Otto Raab

[@Campbellteaching]

+Otto Raab, BScEE Both of these transduct a tactile stimulus into electrical neuronal impulses. However, they are two completely different types of peripheral receptors, different in form and function. Touch receptors are near the surface of the dermis, and lower epidermis, while pressure receptors are deeper in the dermis.

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Thank you for that explanation Dr. Campbell. Now I understand the difference! I enjoy the lectures.

[@gregorymcnally9257]

I thought a Mv was a 1000th of a volt, so when the voltage changes to +30Mv its not a net change of a tenth of a volt from -70Mv. ??

[@yumnaammar7604]

Please, what is the meaning of polarization?

[@notanuragg]

Separation of charges basically

[@shekhar9856]

When action potential in nueron is at rest position

[@paulcrooks4467]

Electrical conduction

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Spatical zone shift.

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☺ thx

[@sumitdhanda6559]

Thank you Sir
I have a few questions
1.Reason for negative charge inside and
2.how the negative charge gone outside ???
Plzz rply

[@pawandissanayake1654]

When there is no nerve impulse passing by..inside the nerve is negatively charged due to chloride ions and few negatively charged proteins , and even positively charged potassium ions are inside the nerve cell, so inside the never cell is said to be negatively charged compared to the outside .when an action potential start to occurs (above -55mV), "voltage gated sodium channels" which are embedded in the nerve cell membrane open so more Sodium ions rushes in.making inside negative and outside positive .

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11:50 like a baws

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Enjoyable

[@tanishqchaurasia5079]

Sir I had a question that do these impulses travel in a particular direction only and if yes then why??

[@pawandissanayake1654]

Tanishq Chaurasia .
1.these nerve impulses are said to be unidirectional (-impulses travel only in one particular direction) because after the action potential, when the nerve cell is repolarizing , before going back to the polarised state at -70mV ,the voltage will drop down to -85mV (hyperpolarisation) and then only return back to the polarised state(-70mV).this period is known as the" refractory period " and No nerve impulse can pass during this period so impulses won't travel backwards .
2 . Synaptic vesicles which contains neurotransmitters are always inside the synaptic bulb in the presynaptic neuron. And sodium ion channels with receptors( receptors that bind with the neurotransmitters)are always located on the post synaptic membrane. This also make action potentials go in one direction.

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[@ifeomammachukwu9727]

Sir,the cell walls is made up of phospholipids.can water from extracellular fluid enter the cell?
How can the different ions exchanged between the intracellular and extracellular fluid.?

[@Campbellteaching]

Yes, ions go in and out through specialised protein based channels Calle ionophores

[@getmoremakonza7085]

Thank you sir