Neurons would need energy to generate those pain 'signals'

[jackson6612]

Hi

A human body is a chemical machine. Every process, such as walking, sleeping, thinking, etc., consumes energy but rate of energy consumption varies from one activity to another. I have been told that when some body part such as forehead, hand, is experiencing, a lot of energy is consumed. This is obvious that neurons would need energy to generate those pain 'signals'. But I'm not sure about that 'a lot energy is consumed'. What do you say on this? Please let me know. Thanks.

 

[bobze]

Hi

A human body is a chemical machine. Every process, such as walking, sleeping, thinking, etc., consumes energy but rate of energy consumption varies from one activity to another. I have been told that when some body part such as forehead, hand, is experiencing, a lot of energy is consumed. This is obvious that neurons would need energy to generate those pain 'signals'. But I'm not sure about that 'a lot energy is consumed'. What do you say on this? Please let me know. Thanks.

Could you clarify the boldfaced?

It depends on what you consider a "lot of energy" that is kind of subjective. Neurons have to constantly use energy shuffling sodium and potassium across their membranes. I suppose compared to other tissues in the body, neural tissue certainly consumes lots of energy.

It is also why neurons are one of the first things to die when you "die". Other tissues can survive "death" for much longer periods because they are "strict" on their requirements to life.

 

[jackson6612]

I'm extremely sorry. I have missed the key word:
I have been told that when some body part such as forehead, hand, is experiencing PAIN, a lot of energy is consumed.

 

[bobze]

I'm extremely sorry. I have missed the key word:
I have been told that when some body part such as forehead, hand, is experiencing PAIN, a lot of energy is consumed.

Okay, that makes more sense .

Well like I said, its really a subjective definition, how much is "a lot".

Certainly when a neuron is transmitting an active message it is using more energy than when it is resting; opening channels, restoring membrane potentials, etc.

 

[jackson6612]

Thanks a lot, Bobze.

Please remember that I'm not a student of biology or science, in general.

That means it does take energy to generate pain signals. I understand pain signals are there to tell us that there is something wrong with the paining area. But what would really happen if that pain was absent? I think pain killers and anesthetics serve the purpose making the pain less painful.

Once again, thanks. I understand it takes time and energy to help others.

 

[bobze]

Thanks a lot, Bobze.

Please remember that I'm not a student of biology or science, in general.

That means it does take energy to generate pain signals. I understand pain signals are there to tell us that there is something wrong with the paining area. But what would really happen if that pain was absent? I think pain killers and anesthetics serve the purpose making the pain less painful.

Once again, thanks. I understand it takes time and energy to help others.

Yes, it takes energy to do just about anything in our bodies, because our bodies like to maintain states that are ordered and in disequilibrium.

If we didn't have pain, we don't fare too well. There are rare genetic diseases where people don't have pain and they typically get into all kinds of trouble.

Even with simple things, you sit in the same position to long and feel uncomfortable, thus you change position. People who don't feel pain, don't do simple things like this and it leads to joint and circulation problems.

Or they do something really off the wall and put their hand on a scalding stove--which obviously is problematic.

Pain is an evolved response to let us know "stop doing that" or "hold that part still" etc. Its integral for organisms to survive.

 

[Borek]

Experiencing pain doesn't use substantially more energy than thinking about that nice chick you have seen in a pub, or solving math problem.

 

[Lievo]

Experiencing pain doesn't use substantially more energy than thinking about that nice chick you have seen in a pub, or solving math problem.

Here you're talking about brain consomption. If we look at the whole body, high level of pain can indeed causes higher energy consomption because of its impacts on the autonomous system.

 

[Borek]

Thinking about the hot chick can make you spend a lot of energy as well, but original question - at least as far as I understand it - was about neurons, not about everything else.

 

[Lievo]

This is obvious that neurons would need energy to generate those pain 'signals'.

Actually this is not so obvious. A neuron needs energy to maintain the chemical gradient, not to fire the action potential. Of course the action potential will impact the chemical gradiant, which then need to be restored. So in the end it requieres energy, but that's indirect.

 

[jackson6612]

Thanks a lot, Bobze. You really cleared it out. Now I understand the good side of pain!

Experiencing pain doesn't use substantially more energy than thinking about that nice chick you have seen in a pub, or solving math problem.

In my opinion it's purely subjective, Borek. Solving a math problem could consume a lot of energy for many like me. Well, that nice chick. The pain of heart is quite different, I believe. And it does consume handsome amount of energy. Thanks for the input.

Here you're talking about brain consomption. If we look at the whole body, high level of pain can indeed causes higher energy consomption because of its impacts on the autonomous system.

Hi Lievo: What's that "autonomous system"? Please let me know.

 

[Borek]

In my opinion it's purely subjective, Borek. Solving a math problem could consume a lot of energy for many like me. Well, that nice chick. The pain of heart is quite different, I believe. And it does consume handsome amount of energy. Thanks for the input.

You didn't get what I was aiming at. It doesn't matter what kind of signals neurons transmit or what kind of task they do - they always use more or less the same amount of energy. It is just like computer - it doesn't matter whether it looks for Mersenne primes or checks spelling of a document, amount of energy is the same.

That's not exactly true, as some tasks may need more resources to be solved, but that's the general idea - energy depends on resources used, not on kind of task. Two tasks requiring same resources require same amount of energy.

Hi Lievo: What's that "autonomous system"? Please let me know.

http://en.wikipedia.org/wiki/Autonomic_nervous_system

 

[bobze]

You didn't get what I was aiming at. It doesn't matter what kind of signals neurons transmit or what kind of task they do - they always use more or less the same amount of energy. It is just like computer - it doesn't matter whether it looks for Mersenne primes or checks spelling of a document, amount of energy is the same.

That's not exactly true, as some tasks may need more resources to be solved, but that's the general idea - energy depends on resources used, not on kind of task. Two tasks requiring same resources require same amount of energy.



http://en.wikipedia.org/wiki/Autonomic_nervous_system

I agree Borek, with what you've said. But, I think the question if directed specifically at those sensory fibers which get activated from a "resting" state--Then they would use more energy (for restoring chemical disequilibrium etc) than during the "resting" state.

Its a rather hard question to address from a layman standpoint in my opinion because different nerve fibers transmit different sensory information. Certainly, as you pointed out the CNS is very active. I took the OP to be referring to the PNS though since he was talking about "transmitting pain" back to the brain.

Suppose then for example, we had some free nerve endings in your finger which monitor heat. You grab a scalding hot pain, many of these fibers which were "not active" will now transmit their message back to the CNS saying "Ow hot". In transmitting the message, since most is saltatory conduction it is "relatively" cheap to transmit. However, the nerve must then expend energy reestablishing its electrochemical gradients etc. Likewise, it would need to take back up neurotransmitters (or make new ones depending on the type of nerve) at the synapse.

Like I pointed out though, how much energy is "a lot"? Its rather subjective. If you placed your whole hand on the stove and activated a lot of sensory fibers saying "Ow" then certainly there's a much greater energy cost than not doing this--in regards to transmitting lots of sensory messages. But that is probably a good energy investment for your body to make

 

[Lievo]

original question - at least as far as I understand it - was about neurons, not about everything else.

You're likely right. However, I don't know any technics to record the total energy consumption of a body part such as the brain -not to mention the neurons. So I guess the information Jackson was told about concerns the body as a whole.

Hi Lievo: What's that "autonomous system"? Please let me know.

Bad name for the autonomic nervous system as Borek mentionned. It controls the para- versus sympathetic systems, and among other functions it is both sensitive to pain and has a lot to do with optimal uses of energy.

 

[Bararontok]

When a person is experiencing pain, it may not be the person's energy that is being used to send the electrical signals to the brain. The energy that is causing the signal to be generated is coming not from the person's body but from the harmful elements of the environment. For example, when a person is blinded by bright light, deafened by loud sound, singed by heat, or stabbed by a knife, the energy that causes the pain is coming from the light, sound, heat and mechanical energy of the external sources and the nerves merely act as electrical generators that will convert this energy into electrical energy to be sent to the brain. The reason why the person uses energy when they are in pain is because the cells that are damaged by harmful forces use energy to regenerate tissue.

 

[Lievo]

@bobze

Just one thing: your points assume that pain is the same thing as nociception. It's not the same. In fact, the most painfull conditions have usually nothing or very little to do with the nociceptive information arising from the peripheral nerves.

EDIT: @Bararontok too

 

[Bararontok]

The energy used to transmit signals depends on the type of pain or problem the person is experiencing. If the pain is caused entirely by the energy of an external source, then the nerves may not need to draw on the person's energy to transmit the signal. But alternatively, the brain uses energy to record the information coming from the signal because it stores information by reconnecting neurons in a different arrangement, it also uses energy to warn the cells in the damaged area to begin regeneration and causes the muscles of the person to contort and tighten to elevate anxiety levels, release adrenaline to raise aggresion, as well as triggering involuntary motor actions that would cause the person to move away from the source of danger. All of this uses energy, so it would be right to say that it is only in the preliminary transmission of information that the body's energy is not used.

 

[Lievo]

then the nerves may not need to draw on the person's energy to transmit the signal

Sorry, but no this does not work this way. Action potentials are dynamically regenerated along the axon. There is no such things as the external energy going through the nerves.

 

[Bararontok]

Yes, because the connections of the neural networks are not permanent like electrical wires and need to be constantly regenerated to ensure a stable connection otherwise the signal will be lost especially since the human body is constantly moving and there is the possibility that nerves will be cut. Because the cells have to increase the electrochemical gradient by releasing sodium ions in order to increase the conductivity of the neural connection and permit more electrical current to flow. Ultimately, energy is required to switch on certain neural connections to deliver specific signals to the brain which will depend on the input stimuli. And even after the damaging stimuli is gone, the nerves still send pain signals to the brain so long as the tissue is physically damaged so this requires that part of the body to generate its own electricity to maintain the transmission of electrical impulses which also uses energy. The energy of the stimuli may be what generates the initial electrical impulse but the other processes that ensure that information is constantly fed to the brain draws energy from the body itself.

 

[Lievo]

there is the possibility that nerves will be cut.

Don't worry too much about that

 

[mishrashubham]

Experiencing pain doesn't use substantially more energy than thinking about that nice chick you have seen in a pub, or solving math problem.

Uh.. Borek.. Can we all please try to make this site more child friendly by not posting testosterone fueled thoughts.

Yes, because the connections of the neural networks are not permanent like electrical wires and need to be constantly regenerated to ensure a stable connection otherwise the signal will be lost especially since the human body is constantly moving and there is the possibility that nerves will be cut.

Nerves don't just get cut while people are moving. They are built into your body system and well protected.

Because the cells have to increase the electrochemical gradient by releasing sodium ions in order to increase the conductivity of the neural connection and permit more electrical current to flow.

Sodium ions are not there for increasing conductivity. These are not your chemical electrolyte solutions where we have passage of electric current between battery ends. They are their to increase or decrease membrane potential.

The energy of the stimuli may be what generates the initial electrical impulse but the other processes that ensure that information is constantly fed to the brain draws energy from the body itself.

Energy from the stimuli (as far as I know) cannot and is not used for any impulse generation.

 

[mtc1973]

Some estimates of cellular energy balance have suggested that in an secretory epithelial cell up to 50% of the cellular ATP consumed is due to Na K ATPase activity. I can only imagine that this figure is equal or greater in a neurone. Thats a lot of energy! So energizing the membrane is a costly business. I should point out though that this process happens irrespective of whether we use the neurone to transmit, i.e. the membrane potential has to be set up anyway - we don't just set it up when we need to transmit. So although there is more energy consumed in an active neurone it may be a small increase over a large resting cost. Remember a tiny amount of ions flow to generate an AP - its not like Na floods the cell and K floods out and we need to reverse that - bulk concentrations hardly move since the required flux to change rmp is tiny!

 

[Bararontok]

Actually from this biology website, it shows that receptor cells generate electrical impulses when subjected to stimuli.

http://leavingbio.net/THE SENSES_files/THE SENSES.htm

 

[Borek]

Does it mean receptor takes energy from stimuli and later neurons use this energy to transfer the signal?

 

[Pythagorean]

It's a matter of physics for physical receptors. For a stimuli to have an effect on a mechanoreceptor or photoreceptor, some energy exchange has to occur between the stimuli and the receptor. As far as I know, it's always from stimuli to receptor (a photoreceptor absorbing light or work being done on a mechanoreceptor).

Not sure how chemoreceptors work in this respect.

 

[mtc1973]

The energization of a neuron is from ion pumps setting concentration gradients. The energy does not carry forward from the receptor interaction.

 

[mtc1973]

Bararantok - don't think anyone would dispute that statement. No one is saying anthing against that simple premise.

 

[Pythagorean]

The energization of a neuron is from ion pumps setting concentration gradients. The energy does not carry forward from the receptor interaction.

Well, yes, but Bararontok already made this distinction. The receptors still need to receive a signal from environment though.

 

[mtc1973]

I was replying to Boreks question. No there is no carry forward of energy.

 

[Borek]

I was replying to Boreks question. No there is no carry forward of energy.

That was a rhetorical question.

 

[mtc1973]

:) I had you pegged for knowing that that was BS already..

 

[Bararontok]

Sodium ions are not there for increasing conductivity. These are not your chemical electrolyte solutions where we have passage of electric current between battery ends. They are their to increase or decrease membrane potential.

Energy from the stimuli (as far as I know) cannot and is not used for any impulse generation.

It says in this source that the membrane potential is a voltage and that the cells function as batteries. Because what is potential but a difference in charge that allows electrons from a region of higher voltage to migrate to a region of lower voltage?

http://en.wikipedia.org/wiki/Membrane_potential

These other sources also say that the sensory receptors convert the input energy of the stimuli into electrical impulses.

http://en.wikipedia.org/wiki/Sensory_receptor

http://en.wikipedia.org/wiki/Sensory_transduction

 

[mtc1973]

The membrane potential is a voltage, no one disputes. But they are not like a battery and wire configuration with charge moving round the circuit, think more like a mexican wave in a stadium a propagating wave of local charge movement across the membrane.

 

[mtc1973]

As for the second bit - receptors do transmit some albeit very little energy in the form of chemical energy. But they are not the source of the energization of the action ppotential. The whole system is an energy continuum, energised by the ion pumps once we get to the action potential. But there is nor sufficient energy in a receptor ligand interaction alone to energise and maintain an action potential. I think that perhaps this is not what you meant, but I and others thought that you were under the impression that the energy from the binding if ligand to a receptor was the driving force for an action potential. When in fact it is the initiator not the energiser. Think starter motor not engine.

 

[Borek]

As for the second bit - receptors do transmit some albeit very little energy in the form of chemical energy.

Quote post you are answering to, it is not clear what you refer to.

 

[mishrashubham]

It says in this source that the membrane potential is a voltage and that the cells function as batteries.

Whenever you cite a source please mention exactly where the statement that supports your claim, lies.

Because what is potential but a difference in charge that allows electrons from a region of higher voltage to migrate to a region of lower voltage?

http://en.wikipedia.org/wiki/Membrane_potential

These other sources also say that the sensory receptors convert the input energy of the stimuli into electrical impulses.

http://en.wikipedia.org/wiki/Sensory_receptor

http://en.wikipedia.org/wiki/Sensory_transduction

Just like mtc1973 said, energy from the stimulus is used as an ignition after which the energy used to carry signal forward is given by ATP; just like an engine where the combustion is started by a small spark which can be said to transfer energy bu to keep the combustion going on you need fuel.

 

[Bararontok]

Yes, I did not say that the energy of the stimuli alone was the cause of the transmission of the signal. I even mentioned that the energy is merely used to switch on the transmission and not to power it.

I even mentioned that here:

The energy of the stimuli may be what generates the initial electrical impulse but the other processes that ensure that information is constantly fed to the brain draws energy from the body itself.

 

[mishrashubham]

I still need thee information from the sources though.

 

[Pythagorean]

I still need thee information from the sources though.

most of it's really in the transduction article, since that's the mechanism of stimuli conversion: 'transduction".

Transduction in the nervous system typically refers to synaptic events wherein a mechanical/physical/etc stimulus is converted into an action potential which is transmitted along axons towards the central nervous system where it is integrated.

For example, in the visual system, sensory cells called rod and cone cells in the retina convert the physical energy of light signals into electrical impulses that travel to the brain. The light causes a conformational change in a protein called rhodopsin. This conformational change sets in motion a series of molecular events that result in a reduction of the electrochemical gradient of the photoreceptor. The decrease in the electrochemical gradient causes a reduction in the electrical signals going to the brain. Thus, in this example, more light hitting the photoreceptor results in the transduction of a signal into fewer electrical impulses, effectively communicating that stimulus to the brain.

(emphasis added)
It's a wiki article with no references, but it conforms to my general understanding from my neurobiology course and the basic idea that the stimuli isn't an energy source, but a kind of "switch". Though "switch" is oversimplified, really. The more interesting receptors are actually resonators rather than integrators. That is, they respond to particular phases/frequencies of stimuli, not a simple threshold value (for instance, the hairs cells in your ear).

 

[mishrashubham]

most of it's really in the transduction article, since that's the mechanism of stimuli conversion: 'transduction".


(emphasis added)
It's a wiki article with no references, but it conforms to my general understanding from my neurobiology course and the basic idea that the stimuli isn't an energy source, but a kind of "switch". Though "switch" is oversimplified, really. The more interesting receptors are actually resonators rather than integrators. That is, they respond to particular phases/frequencies of stimuli, not a simple threshold value (for instance, the hairs cells in your ear).

Thank You Pythagorean

 

[thorium1010]

Yes, I did not say that the energy of the stimuli alone was the cause of the transmission of the signal. I even mentioned that the energy is merely used to switch on the transmission and not to power it.

I even mentioned that here:

The energy of the stimuli may be what generates the initial electrical impulse but the other processes that ensure that information is constantly fed to the brain draws energy from the body itself.

The means by which a neuron carries a signal is depolarization , read about depolarization.
http://en.wikipedia.org/wiki/Depolarization"

http://en.wikipedia.org/wiki/Action_potential"

read about action potential.

Its not so much as a electrical signal, rather depolarisation of membrane potential that carries the signal along the nerve.

The initial stimulus if crosses a threshold is able to depolarize the membrane of nerve which further leads to depolarization along the nerve propagating as a signal. This is energy dependent (ie atp) since energy is required to maintain the membrane potential.

 

[Bararontok]

This is quoted directly from the source:

http://en.wikipedia.org/wiki/Depolarization

Because depolarization is a change in membrane voltage, electrophysiologists measure it using current clamp techniques. In voltage clamp, the membrane currents giving rise to depolarization are either an increase in inward current, or a decrease in outward current.

So the depolarization process is what performs the switching action that permits current to flow. Because if two potentials are of equal and like voltage, their forces will cancel out and no electrical current can flow, but if one end of the nerve line has a lower or opposite polarity for voltage, then the region of higher potential will induce a current which will travel to the region of lower potential, thus causing a flow of electrical current.

 

[mtc1973]

Baron - there still seems to be some misunderstanding. Current does not flow down a nerve. The potential us not set up between one point On the nerve and another, it is set up across the membrane. I am by the way an electrophysiologist and have spent years patch clamping doing whole cell measurements, you just need a basic physiology textbook - and some time to get this correct. These wiki articles you quote are quite fine but there seems to be a fundamental misunderstanding on how an impulse us generated and maintained. I'll dig out a good source tomorrow and post.

 

[mtc1973]

In the upper laft (sorry I couldn't post the pic had to attach) this is resting state. The iside of the axon is net negative charge and the outside net positive - largely due to the fact that K channels in the membrane are open and holding the membrane potential at a negative value (i.e. K initially leaves the cell - leaves the inside net negative then K flux stops at the membrane potential is generated and balances the K flow). This is all energized by the Na K ATPase - which is burning up ATP by the minute keeping the K gradient - this is where the energy is consumed! So without even initiating a nerve impulse we are burning up energy constantly. Na channels in the membrane are then triggered to open by some external stimulus (like pressure at a pressure transducer in the skin), leading to Na coming into the cell - and since it is a positive charge the cell interior now has a positive charge (outside negative), i.e. the membrane potential has changed. This actual flow in terms of amount of ions though - is tiny, very small indeed. i.e. only a few million ions need to flow to change the membrane potential at that point (this is minuscule compared to the standing ion gradinets - which is why there is no great energy consumption to correct this ion flux - the background energy consumption of keeping the huge concentration gradient in the first place outweights tiny amount of Na that comes into the cell - and will then have to be pumped back out). This change in membrane potential as Na comes into the cell - is sensed by other Na channels and they too open. The Na channels remains open for a very short duration and then automatically closes. So this wave of depolarization is what travels along the axon - but in no way does charge flow along the length of the axon. It is a traveling wave of local depolarization. Any good physiology textbook will cover it in detail. Sorry for the delay.

And remember - the main energy consumtion comes from setting up the K gradient and Na gradient in the first place. Not by the passing of the action potential. Hence there is a huge resting cost to keep membrane potential but a fairly insubstantial cost to actually then use that stored energy. Think of it like a battery on constant charge - and then we use a little of the battery power and then switch it straight back to charge again. You power consumption comes from the charging - not the battery usage.

 

[jackson6612]

MTC, did you scan the drawing or draw it on the screen? Just curious to know.

 

[mtc1973]

Pencil paper and scan.

 

[jackson6612]

Thanks for letting me know.

 

[Bararontok]

So in conclusion, the signal is propagated by the constant depolarization from one cell to another and this is what allows the electrical signal to travel through the neural network. The energy of the stimuli opens the channel for the sodium ions which will flow out, change membrane potential, and cause a voltage to flow between two membranes due to the potential difference before the sodium ions then flow to another cell membrane. Thus the flow of electrical impulses is intermittent since it can only flow between two membranes while it is the current of sodium ions that permit this short range transmission of signals to travel a long distance through the neural network.

 

[sameeralord]

I think you have to consider adaptation as well. When a stimulus of constant strength applied and maintained on a receptor, the frequency of the action potentials in its sensory nerve declines over time. Can anyone tell me how this occurs.

 

[mtc1973]

Experimentally you can demonstrate adaptation. If you trigger an action potential by eg a 20 mv depolarisation of membrane potential. Now if you do say 2 or 3 smaller pre depolarizations and then do 20 mv depolarisation as you initially did then you no longer see an action potential. The reason is that chronic depolarisation even if quite small causes the sodium channel to go into a locked closed configuration - so no further action potentials are possible. There are also mechanisms by which the receptor system itself can accommodate, those will be specific to the specific receptor system involved.