Time between when you touch something hot and your brain says " PAIN ! " ?

Dave Carpentier

So you choose to touch something to see if its hot.
Our nerves respond pretty quick to the initial message, but why the long-ish period until you start to feel the pain itself ?
Do either of those get slower as we age ?
Im pretty sure we suffer damage at a quicker pace (and longer recovery) as our skin ages.

EdTheHeaterMan

It may be that some brains are smart enough to keep their fingers away from the hot stuff in the first place. But then again, my brother-in-law has been a carpenter for his entire adult life. I can see why some brains are different than others. Dave Carpentier.

Just sayin'

ChrisJ

Dave Carpentier said:

So you choose to touch something to see if its hot.
Our nerves respond pretty quick to the initial message, but why the long-ish period until you start to feel the pain itself ?
Do either of those get slower as we age ?
Im pretty sure we suffer damage at a quicker pace (and longer recovery) as our skin ages.

I'm not sure if it changes with age, I suspect it doesn't.
However, I do approach slower to see if I can feel the infrared off of the object.

dko

From googling:

1st question

Pain signals are carried in nerve fibres to your brain.

About 10% of those pain fibres, technically A-delta fibres, carry signals as fast as any nerves in your body, about 200 metres per second.

So as soon as your hand detects a painful stimulus (like the hot water), the A-delta fibres carry that signal, not even as far as your brain, but only your spinal cord, where it results in a powerful withdrawal response: pull your hand away! When this signal reaches your brain, you get the first perception of pain: OUCH! But by then your hand is already out of the water.

But meanwhile, the other 90% of your pain fibres, the c-fibres, which started at the same time (same stimulus, same pain), are carrying the signals more slowly. C-fibres lack myelin, so they carry more slowly (about 2m/sec). It takes those signals a bit longer to reach your brain, and that’s why you feel that second surge of pain about a second after you’ve taken your hand away from the hot water. It often feels greater because there are so many more c-fibres, so the signal is stronger.

What you’re experiencing is the time delay between two different sets of nerves doing the same thing, one faster than the other.

2nd question

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565621/
https://journals.lww.com/pain/Abstract/1996/01000/The_effect_of_age_on_A___and_C_fibre_thermal_pain.16.aspx (abstract only, need to sign up for full study)

WMno57

Found this:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347309/
"Elderly individuals are more vulnerable to burn injury due to their limited mobility coupled with their physical inability to react rapidly and reach safety when faced with danger. Mabrouk et al.5 reported that when caught in a fire, 23.7% of the elderly collapse, which aggravates their injuries. Albornoz et al.6 have also highlighted decreased protective mechanisms in the elderly due to decreased sensitivity and atrophic skin. The propensity of geriatric patients to burn injuries is accentuated by pre-existing medical problems in conjunction with impaired vision, decreased coordination, and the side effects of medication.7 In addition, increased age is associated with increased dependence and requirement for assistance with activities.8,9 While children and young adults manifest improved survival rates, elderly individuals suffer from a disparate increase in morbidity and mortality following burn injury.9 In fact, age has consistently been shown to be a strong predictor of in-hospital mortality among burn patients,9 its impact well influencing survival up to two years after the initial injury.9"
Also, the Elderly are more susceptible to Legionnaires disease
So install a mixing valve. Mix 140 down to 120.

• Keep water temperature either above or below the 20–50 °C (68–122 °F) range in which the Legionella bacterium thrives.
  
• Prevent stagnation, for example, by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, as when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation.
  
• Prevent the buildup of biofilm, for example, by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system.
  
• Periodically disinfect the system, by high heat or a chemical biocide, and use chlorination where appropriate. Treatment of water with copper-silver ionization or ultraviolet light may also be effective.[33]
  
• System design (or renovation) can reduce the production of aerosols and reduce human exposure to them, by directing them well away from building air intakes.
  

https://en.wikipedia.org/wiki/Legionnaires'_disease#Prevention

Can Heat Pump Water Heaters be set to 140 Fahrenheit? Will they maintain 140?
Will "Grid Aware" HPWH throw old people under the bus to save the grid and "the planet"?
@JakeCK found his HPWH had a mind of it own. He would command the user interface to not use resistance elements, but it would anyway.

Jamie Hall

I'm no biologist. A field of science which I never got into at all. So my comments are empirical, from observing myself over the past 8 plus decades... my reaction time is definitely slower. More with regard to complex surprises -- why elderly folk need to be especially careful if they drive, if they drive at all -- but also I think perceptibly slower with regard to things like touching hot stuff. This is not, however, related to decreased mobility at least in my case, although I can see it would be in some.

Perception of pain -- a completely different nerve pathway, by the way, that much I do know -- varies so widely among individuals that I have no idea why it would be slower -- except that it is a perception (brain mediated) not a reflex.

Of course, if one has spinal cord problems, reflexes will be slowed profoundly (or even not present at all --often with lack of other sensations or partial paralysis)-- and pain may be present of increased with no associated reason for it. I have several friends in my age group who have such problems. Not fun. Take care of your back.

ethicalpaul

It takes time for the heat to conduct to the nerves. Touch with your finger pad takes way longer to feel it than touch with the underside of your arm.

Then by the time the heat gets to your nerves under that thick finger skin, all that skin is heated up so the pain persists longer too.

Here's an interesting article where the reaction of intense pain bypasses the brain altogether: https://mydr.com.au/pain/pain-and-how-you-sense-it/#:~:text=Motor neurones are activated and,becoming conscious of the pain.

hot_rod

When it comes to the elderly folks and excessively hot shower or tub water, often times you end up with both a burn and a slip and fall as they react to get out of the hot water and fall on the floor.
Julius Ballanco, a now retired forensic M.E. related that observation to me years ago.

I know my skin seems to cut and burn easier now then when I was 30, 40...

ChrisJ

hot_rod said:

When it comes to the elderly folks and excessively hot shower or tub water, often times you end up with both a burn and a slip and fall as they react to get out of the hot water and fall on the floor.
Julius Ballanco, a now retired forensic M.E. related that observation to me years ago.

I know my skin seems to cut and burn easier now then when I was 30, 40...

I find it best to set the water temp before I get into the shower.

The beginning of the shower scene in Psycho is one of the scariest things I've seen. She gets in and then turns the shower on. A nice cold blast of water.............

Jamie Hall

hot_rod said:

When it comes to the elderly folks and excessively hot shower or tub water, often times you end up with both a burn and a slip and fall as they react to get out of the hot water and fall on the floor.
Julius Ballanco, a now retired forensic M.E. related that observation to me years ago.

I know my skin seems to cut and burn easier now then when I was 30, 40...

Oh dear. Isn't that true... I just try not to drip on whatever I'm working on...

tim smith

I remember when I misdirected my oxy acetylene torch over the backside of my left hand. Blew the skin clear off, surface was almost white. Pain settled in about 20 min after the shock of it. Don't wish to do that again.

reggi

Dave Carpentier said:

So you choose to touch something to see if its hot. Our nerves respond pretty quick to the initial message, but why the long-ish period until you start to feel the pain itself ? Do either of those get slower as we age ? Im pretty sure we suffer damage at a quicker pace (and longer recovery) as our skin ages.

Sounds like 2 different things, 1 . You're wanting to know if it's hot so you touch it...
2. Once you discover it's hot subconsciously you want to find out how hot it is,.. If it was a glowing red pipe that you had a torch on you wouldn't approach it the same way,, right ?

ChrisJ

reggi said:

Dave Carpentier said:

So you choose to touch something to see if its hot. Our nerves respond pretty quick to the initial message, but why the long-ish period until you start to feel the pain itself ? Do either of those get slower as we age ? Im pretty sure we suffer damage at a quicker pace (and longer recovery) as our skin ages.

Sounds like 2 different things, 1 . You're wanting to know if it's hot so you touch it...
2. Once you discover it's hot subconsciously you want to find out how hot it is,.. If it was a glowing red pipe that you had a torch on you wouldn't approach it the same way,, right ?

Is it glowing or is it painted safety orange?

JakeCK

WMno57 said:

Found this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347309/ "Elderly individuals are more vulnerable to burn injury due to their limited mobility coupled with their physical inability to react rapidly and reach safety when faced with danger. Mabrouk et al.5 reported that when caught in a fire, 23.7% of the elderly collapse, which aggravates their injuries. Albornoz et al.6 have also highlighted decreased protective mechanisms in the elderly due to decreased sensitivity and atrophic skin. The propensity of geriatric patients to burn injuries is accentuated by pre-existing medical problems in conjunction with impaired vision, decreased coordination, and the side effects of medication.7 In addition, increased age is associated with increased dependence and requirement for assistance with activities.8,9 While children and young adults manifest improved survival rates, elderly individuals suffer from a disparate increase in morbidity and mortality following burn injury.9 In fact, age has consistently been shown to be a strong predictor of in-hospital mortality among burn patients,9 its impact well influencing survival up to two years after the initial injury.9" Also, the Elderly are more susceptible to Legionnaires disease So install a mixing valve. Mix 140 down to 120.

• Keep water temperature either above or below the 20–50 °C (68–122 °F) range in which the Legionella bacterium thrives.
• Prevent stagnation, for example, by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, as when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation.
• Prevent the buildup of biofilm, for example, by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system.
• Periodically disinfect the system, by high heat or a chemical biocide, and use chlorination where appropriate. Treatment of water with copper-silver ionization or ultraviolet light may also be effective.[33]
• System design (or renovation) can reduce the production of aerosols and reduce human exposure to them, by directing them well away from building air intakes.

https://en.wikipedia.org/wiki/Legionnaires'_disease#Prevention Can Heat Pump Water Heaters be set to 140 Fahrenheit? Will they maintain 140? Will "Grid Aware" HPWH throw old people under the bus to save the grid and "the planet"? @JakeCK found his HPWH had a mind of it own. He would command the user interface to not use resistance elements, but it would anyway.

Yes a hpwh can get to and keep 140f water. Mine does it every day.

Grid aware water heaters should never go above the set point, so no it won't throw old people under the bus. If it did adjust the temperature I set it too I would disconnect it from the network. If the utility had a problem with it, I'd tell them it must be broked and me no understand.

My hpwh does not have a mind of its own. To clarify it only turned the elements on when it detected it couldn't keep up and the water was getting too cold. It displayed the error on both the device it self and on the app. It has only happened once in the middle of January, I think, on a day that we had unusually high demand. And it only ran the elements for maybe 10-20 minutes tops. It made little to no difference in overall energy usage. 

Now with all that said 140f with a mixing valve set to 110-120 is the way to go. No risk of bacteria and no risk of scalding hot water. 



And I've noticed my reaction times slowing down even at the age of 35 vs when I was 20. I played video games heavily when I was younger. First person shooters and such that rely on very fast reaction times where 50ms can mean the difference. I used to play those games on dialup with a ping of over 350ms and could hold my own against those on broadband. Today if I get matched against someone in their teens even on my fiber internet and it's sub 10ms latency I can hardly compete. It's disturbing tbh. I'll watch the replay footage thinking they're cheating or something and nope the kids just respond faster then I can. I used to be that fast. Now I have to rely on strategy to beat them. 

Is it a large change no? In the real world it is of little consequence, but it does show up. A measurable change that slowly increases overtime. 

Jamie Hall

Just you wait, @JakeCK , until you are my age! Fortunately I noticed the slowing decision loop reaction time, and gave up flying and spirited driving... before either I did something dumb or my daughter got on my case. (I still miss the flying... but I wouldn't be safe any more)

reggi

ChrisJ said:

reggi said:

Dave Carpentier said:

So you choose to touch something to see if its hot. Our nerves respond pretty quick to the initial message, but why the long-ish period until you start to feel the pain itself ? Do either of those get slower as we age ? Im pretty sure we suffer damage at a quicker pace (and longer recovery) as our skin ages.

Sounds like 2 different things, 1 . You're wanting to know if it's hot so you touch it...
2. Once you discover it's hot subconsciously you want to find out how hot it is,.. If it was a glowing red pipe that you had a torch on you wouldn't approach it the same way,, right ?

Is it glowing or is it painted safety orange?

No safety 🦺 orange , tomato 🍅 red , 

Larry Weingarten

Hi, As we're talking colors now, perhaps this chart from Tube Turn will help.

Most of these temps will turn me into steam way too fast!

Yours, Larry

JUGHNE

Using soft solder for plumbing, often a drip would land on my hand, that was tolerable.

But if a drop landed on a fingernail, the hand went into the water bucket (learned to always have one handy when soldering). Unbelievable how much that hurts, when the hand can be ok catching hot solder.

ChrisJ, yes I noticed the shower valves in Psycho, wondered why not turning it on first.
But only observed that after watching it later in life.

I saw the movie when it first came out and there was more to see, or at least look for, as a younger lad years ago....shower valve handles were not a priority then.

Dave Carpentier

Colouring hot things white just wouldnt seem obvious to people. Red must be a primitive connection to fire.

@JUGHNE - In the first part of my career we torch soldered (and unsoldered) lead pipe "sleeves" up to 12" dia onto telecom cables underground. Got hit with many solder splats, but never on the fingernail. Glad I didnt lol. Worst one i can remember is laying on the manhole floor unsoldering a splice just above my chest. One small blob got away on me and landed on the side of my neck. I got it off right quick but had the small hickey for a while..