The Science Behind Touch

I’ve written about the science behind acquired taste and cybernetic eyes. I planned to touch on the other senses. (Pun intended!) What better time to investigate the science behind touch, since two scientists have won a Nobel Prize for the discovery of touch receptors. Using seemingly random items; chili peppers and pipettes!

The Science of Touch_Chili peppers
Chili peppers!
Touch Receptors_Make sense of science_pipette
Pipette!

THE SCIENCE BEHIND TOUCH

Which sense do you think people most take for granted?

I did a twitter poll a few months ago and asked people to vote on their favorite sense

Touch received ZERO votes.

My tweets here

​"In science many times it's things we take for granted that are of high interest." --Ardem Patapoutian 

Touch Receptors_Make sense of science_pipette

I bet you a pizza that Dr. Patapoutian (one of the Nobel prize winners) would have voted for the sense of touch!

Make Sense of Science_Join us_Subscribe
We all voted with a write-in for dogs!

HOW DOES TOUCH WORK?

Touch is an elemental function of the nervous system, which is how we react with our environment!

Let’s start with a quick review of the science of touch.

What better way than with a mini guide of signaling in the human nervous system. Yes, a touch of science!

 

Science Behind Touch_Louie the science dog
What about the cuddly receptor?
Science Behind Touch_not neurons
Louie just reminded me that my OPTIONAL canine quiz garnered next to no attention. Click on the pic to take a peek.

There will be no neuron quiz today.

THERE WILL BE A QUICK TOUCH OF SCIENCE ALA REVIEW OF THE NERVOUS SYSTEM...I promise it's speedy quick! (yes, another pun)

WHAT ARE NEURONS ANYWAY?
A neuron is a nerve cell that is the basic building block of the nervous system.
Neurons are specialized to transmit information throughout the body
Neurons release chemicals known as neurotransmitters into synapses, or the connections between cells, to communicate with other neurons.
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Since we're talking about touch, in this post we're referring to specifically sensory neurons.

They're part of the somatic nervous system.

Sensory neurons carry information FROM the sensory receptor cells throughout the body TO the brain.

Science of touch_nervous system diagram
Just the circled box!
Diagram ganglion and paths of a alpha, beta delta
Yes, even a little box can get complicated. Let's back it up.

A FEW TOUCH RECEPTORS TO INCLUDE HEAT, COLD, PAIN, PRESSURE, PROPRIOCEPTION (where we are in space!)

I bet you’re saying to yourself, ‘what’s the big deal with discovering sensory neurons?’ We know  the touch receptors are there, especially when we step on a bee or our hot cocoa is too hot.

Make Sense of Science eye roll
What's the big deal?

The big deal was that scientists didn’t know where the receptors that stimulated the sensory neurons were located, not exactly. ‘In our skin’ doesn’t cut it. Unless we get a cut. (There won’t be blood in this post either.)

 

Scientists had been searching for touch and temperature receptors for many years. Everyone knew they were there somewhere, but no one knew where they were.

baby elephant
Touch receptors were the elephant in the room!

Here’s some of what we did know before the discovery of the touch receptors!

SOME HISTORY OF THE SCIENCE BEHIND TOUCH

René Descartes who said...
"Cogito Ergo Sum" = "I think, therefore I am."
René Descartes hypothesized that particles of fire pulled a thread between the skin & the brain
Give him a break. It was 1639.
Flash forward to the 1880's
Distinct sensory spots on the skin were shown to react to specific stimuli, (touch, heat, or cold) indicating that different stimuli activate different types of nerves
In the 1890s, Charles Sherrington & Edgar Douglas Adrian showed how neurons function.
Must have been some dissection going on.
In 1906 came a huge discovery
Camillo Golgi & Santiago Ramón y Cajal proved that all nerve cells in the nervous system constituted a continuous, interconnected network.
The nervous system was a system!
These guys did a lot of investigation of the brain and neurons.
Click Here
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The concept that the nervous system was a system, was so important that they– not sure who ‘they’ are–named an organelle (part of a cell) after Camillo Golgi.

Okay, Golgi discovered Golgi bodies but still. Golgi & Cajal aren’t exactly household names yet they did important work.

touch receptors_ Golgi bodies
Golgi bodies help process and package proteins and lipid molecules
Filo dough golgi bodies
Filo dough looks like golgi bodies except far more delicious.
In 1944, two scientists divided nerve fibers into two different types with different thicknesses and showed that the thicker fibers convey nerve impulses faster.
They discovered the highly differentiated functions of different nerves!
Click Here

A post about nerves and the science of touch  wouldn’t be complete without touching on pain. (pun # 3 for the win) And if you’re interested in the intrigue of poisons, which also cause pain, click here.

THE SCIENCE BEHIND TOUCH : PAIN

Maybe people don’t care to think about touch because of the negative connotations. AKA PAIN.

I do the research so you don't have to_Make Sense of Science
Not the pyschological pain of wearing the dunce cap. Physical somatic nervous system pain.
Science Behind touch___Emily Dickinson
Shout out for Emily Dickinson!
Make Sense of Science_Wow This is cool_Alex
You've got my attention!
Pain defined in a less poetic way:
Pain is a protective mechanism that will encourage the body to withdraw or avoid some exogenous injurious stimulus.
Click Here
THERE ARE 2 DIFFERENT TYPES OF PAIN FIBERS
We learned about different nerves in 1944
1) A-delta fibers
They're the 'oh sh*t' fibers . They kick in quickly.
Click Here
2) C-fibers
They are the groan fibers. They're slower so you notice the pain from C-fibers several seconds following an injury.
Why are the A-delta fibers faster, you ask?
GOOD QUESTION!
A-Delta fibers are myelinated meaning they have a special coating around the nerves
Myelination (the special coating) allows conduction to travel faster
like rubber around a telephone pole
Myelinated means fast.
If you were a sprinter, you’d want to be myelinated!
C-fibers are unmyelinated & thinner.
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A-delta and C-fibers

Because of myelination & diameter differences, painful stimuli from A-delta fibers arrive in your brain before those same painful stimuli from the C-fibers. But the C-fibers place in the pain race.

How nice for us! 

How does touch work__ A delta and C fibers
A photo is worth 1000 words, unless it's a poem.

 The A-delta fibers send the “first pain” into the brain.

C-fibers travel more slowly, so you notice the pain from C-fibers several seconds following an injury.

 

Touch of science _A delta fibers
A-delta for the win!
The Science Behind Touch_pain
More of a throbbing pain. So C-fibers!

THE SCIENCE BEHIND TOUCH : PROPRIOCEPTION

Here’s another example of something we take for granted. Proprioception. 

The sense that lets us perceive the location, movement, and action of parts of the body is proprioception or kinesthesia.

A-alpha fibers are the proprioceptive fibers and easily the fastest. Why?

Science Behind Touch_Proprioception_Louie Eeyore
Proprioception on point.

We have to know where our limbs are in space at any given time!

A-alpha fibers are myelinated & thick, so they get the job done & we don't fall down or bang into things. (toe stubbing not included)
Science Behind Touch_proprioception_Louie
This guy's proprioception better be functioning!

Now that we’re up to A-alpha myelination knowledge speeds, let’s get to the newest discovery!

HOW DOES TOUCH WORK?

These two scientists won the 2021 Nobel Prize for Physiology or Medicine for answering the million dollar question:

How are temperature and mechanical stimuli converted into electrical impulses in the nervous system?

(It doesn’t sound as exciting when I type ‘physiology or medicine’ as if they aren’t important enough to have their own category!)

Ardem Patapoutian-Nobel Prize touch receptors
Ardem Patapoutian credit Ill. Niklas Elmehed © Nobel Prize Outreach
David Julius nobel prize physiology
David Julius credit Ill. Niklas Elmehed © Nobel Prize Outreach
Using capsaicin, a compound that gives chili peppers their distinctive burning sensation, Julius was able to identify a receptor in the nerve endings of skin that responds to heat.
Click Here
TRPV1
His experiments revealed that this receptor, which he called TRPV1, is an ion channel that is activated by painful heat.
TRPM8
Independently of one another, both David Julius and Ardem Patapoutian used the chemical substance menthol to identify TRPM8, a receptor that was shown to be activated by cold.
Click Here
THEY DISCOVERED THE ICY HOT RECEPTORS!
Patapoutian and his co-workers succeeded in identifying a single gene whose silencing rendered the cells insensitive to poking with the micropipette.
IOW...
A new and entirely unknown mechanosensitive ion channel had been discovered and was given the name Piezo1, after the Greek word for pressure
Click Here
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HOW DOES TOUCH WORK...ION CHANNELS

TRPV1 is an ion channel activated by painful heat. 

TRPM8 is an ion channel that is activated by cold. 

 Piezo1 and Piezo2 are opened by mechanical force.

 

What does all that actually mean?

Make Sense of Science_don't look dorky with your kayak paddle
Waving a kayak paddle round won't help a thing, not even to kayak.
Ion channels can be thought of as pores in our cell membranes
Pores made of proteins
Even though ions travel across these proteins, I personally think that 'ion channels' is misleading.
No one asked me.
Did you see that lip on top of the protein on the right in the last slide?
"Gated" means that the protein opens and closes in response to stimuli
Ion channels are specialized proteins in a cell membrane that provide a passageway through which charged ions can cross down their electrochemical gradient.
More on ion channels here
The TRPV1 protein has been nestled inside of cell membranes all this time.
The lip opens when the temp. increases.
Click Here
This opening of the TRPV1 'pore' elicits a sensation of burning pain by selectively activating sensory neurons.
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THESE NEWLY DISCOVERED RECEPTORS RESPOND TO HOT & COLD!

How does touch work _ _Graph temperature and TRPV1 TRPM8
An excellent graph of the temp that stimulates the newly discovered receptors & their impulse speeds

NOW THAT YOU KNOW ALL ABOUT THE SCIENCE OF TOUCH, WHY DOES THIS MATTER?

The groundbreaking discoveries of the TRPV1, TRPM8, and Piezo channels by this year’s Nobel Prize laureates have allowed us to understand how heat, cold and mechanical force can initiate the nerve impulses that allow us to perceive and adapt to the world around us.

Nobel Committee press release Tweet

The identified ion channels are important for many physiological processes and disease conditions.

We’ve come a long way learning about the science behind touch since Descartes.

HOw Would Humans Live on MArs__I won't go without coffee_Kev
Almost as important as the discovery of caffeine! Click on my smile to read about caffeine.

MORE TOUCH RECEPTORS ARE POPPING UP!

The Science of touch_ Mechanical heat and cold touch receptor IMAGE CREDIT Fernandez Cavarjal et al. Pharmaceuticals 2012 5(1) 16-48s
Which ion channel receptors respond to what stimuli

PIEZO PROTEIN ION CHANNEL APPLICATIONS

Remember that silencing the Piezo gene renders the cells insensitive to poking with a micropipette! In theory, silencing touch / proprioception could help with issues such as mechanical (joint) pain, respiration, blood pressure, and skeletal remodeling. 

respiration

TPV1 PROTEIN CHANNEL APPLICATIONS

And the TPV1 channel could be closed, thus decreasing issues such as inflammatory pain, lower core body temperature due to high fevers, dampen protective reflexes or aid with neuropathies and visceral pain.

foot pain

PERIPHERAL NEUROPATHY AND DIABETES

How about peripheral neuropathy and diabetes! It would be cool to  do the opposite &  stimulate the TPV1 channels, so people w/o sensation would notice if they stepped on a thumbtack or cut themselves. They could take care of  their injuries instead of getting infections.

Great news Make sense of science copy
That would be cool!

Patapoutian & Julius’ discoveries could lead to the development of non-opioid painkillers and treatments for “a wide range of disease conditions, including chronic pain.”  

A touch of science_ Joiin us_ subscribe to Make Sense of Science
No more reliance on opioids? No more chronic pain? Booyah!

THE SCIENCE BEHIND TOUCH

Let’s give it up for these scientists. They identified critical missing links towards  understanding how our bodies respond to the world around us.

And when they use their Nobel prize money–an equal split of $1.1 million–to host a pizza party for their lab staff, you can be sure everyone knows the mechanism when they burn their hard palates!

Louie says subscribe to Make Sense of Science
I wish I could go. I've never had pizza.

What do you think about the science of touch & these amazing discoveries? Imho,  scientists should be paid as much as athletes!

Lionel Messi
Soccer player Lionel Messi $130.0M in 2021
Conor McGregor
MMA fighter Conor McGregor $180.0M in 2021

I do the research so you don't have to! (I agree, that guy should shirt it up)

SHIRT OR NOT, SUBSCRIBE & YOU'LL STAY ON THE CUSP OF EMERGING SCIENCE

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56 thoughts on “The Science Behind Touch”

    • Great question. Our skin doesn’t have wetness receptors so the pathway is more complex. Researchers -so far- have found that A-fibers are involved and that wetness perception increases with lower temp water. We need to be more careful with hotter water. Thanks so much!

      Reply
  1. What an interesting article.

    I love hearing about new topics and learning something different.

    The format is also great and love the quotes and images. Maybe not the broken glass one. Ouch.

    So informative. I feel like I’ve learnt something new for today 👍

    Reply
    • I’ve been taking the sense of touch for granted, too! I put some of the more dense info in slides, which –in my wee brain– makes it more accessible. Or more easily skipped! ha! Thank you for stopping by!

      Reply
  2. Wow, this is so interesting! The human body is an amazing, complex machine. I love your slide shows and all the great pics, especially of Louie. Thanks for enlightening me.

    Reply
  3. Wow! What an amazing blog! I love the little slideshows. It breaks the reading up nicely! You are a great writer! I’ve learned a lot about the science of touch! X

    Reply
  4. The research and time that you put into each and every one of your blog posts always leaves me in awe! I am quite a touchy feely person with the people I love. When I’m unwell, the touch of my husband instantly makes me feel better – even just having him near me is like instant pain relief. It may a placebo for me but if it works, it works!
    Rosie

    Reply
    • That your husband can comfort you is not a placebo! It’s a complex science, incorporating neural pathways, repetition, and positive reinforcement ala endorphins. Your brain is actually wiring itself for pain relief ala your cozy spouse! I’m happy that you have him. Thanks so much.

      Reply
  5. What amazing systems/bodies we all walk around with and never realize it. And since there was no neuron test, I’m quite sure now I would have aced it 😉 Thanks for your hard work on these posts!

    Reply
    • I’m sure you would have aced the neuron quiz, too! It is amazing that we walk around while our bodies are silently working away! Lionel Messi may disagree, but science is far more fascinating than soccer. Thanks, Eileen!

      Reply
  6. Hi Sue,
    Informative and great visuals as usual. I also appreciated the woman’s comment about how her husband’s touch can immediately make her feel better. Endorphins might be an interesting future topic.

    Reply
  7. The research and time you put into each of your posts is just amazing and I can’t thank you enough for it. I found this so interesting to read and learnt so much I didn’t know about the science behind touch. It’s incredible how the body works isn’t it? Xo

    Elle – ellegracedeveson.com

    Reply
  8. I will admit, things like this tend to go over my head, I don’t really understand this sort of stuff but it was an interesting read nonetheless! They definitely need to go into more understandable detail about this in schools!

    Reply
  9. Very interesting post. I also enjoy the photos and slideshows (especially the Louie photos :). I’m very hopeful about new treatments for all of my chronic pains!

    Reply
  10. This post is so informative. As a nurse, I definitely know the impact of touch on showing care and empathy for others. I also know what if feels like to have altered sensation . I sustained nerve damage to my foot two years ago and still feel pins and needles. It’s important to be mindful of all of our senses.

    Reply
  11. The body is home to many different systems of nerves, bone, flesh, and muscle yet each one, in its own function, is as intricate and detailed as the next. The immense amount of design and function that goes into something as given as touch is amazing, and I love how you have broken it down in a fun and illustrated way. 🙂

    Reply
    • I was going to break down another cool mechanism of the somatic nervous system and how it incorporates our skeletal muscles (The Withdrawl Reflex) but decided I’d gushed about sensory neurons enough! Another time. You’re right; our bodies are intricate, detailed, and intriguing. Thanks, Jaya!

      Reply
  12. This post is so interesting! I would definitely have chosen another sense in the poll, forgetting about touch. Which is funny because I have two chronic illnesses that come with chronic pain. I am very hopeful for future breakthroughs in helping chronic pain. Your posts are always so informative and I can see the amount of work that goes into them 🙂

    Reply
  13. Excellent explanation of pain. I wonder how many pain fibers Aaron Rodgers stimulated in packer land with his recent story about his so called immunization. What a pain in the blank blank blank blank! Great job as usual. Mike

    Reply

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Susan Berk Koch author

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