Hi there! Welcome back to NeuroTransmissions.
Hi there! Welcome back to NeuroTransmissions.

So we’ve learned about all of our other main senses: sight, sound, smell, and taste.
So we’ve learned about all of our other main senses: sight, sound, smell, and taste.

Now we’re back to talk about the final sensory system - your sense of touch.
Now we’re back to talk about the final sensory system - your sense of touch.

Somatosensation is enormously important; how else would you tell the difference between
Somatosensation is enormously important; how else would you tell the difference between

the gentle touch of a feather and the scratch of sandpaper?
the gentle touch of a feather and the scratch of sandpaper?

How could you tell if you were wet, or hot, or too cold? Most of all, how could you tell
How could you tell if you were wet, or hot, or too cold? Most of all, how could you tell

if you were in pain? Don’t touch that dial...until you find out.
if you were in pain? Don’t touch that dial...until you find out.

All somatosensory pathways have the same basic structure, so let’s focus on one and then
All somatosensory pathways have the same basic structure, so let’s focus on one and then

talk about some variations.
talk about some variations.

Let’s say I reach out and touch your arm. How do you feel it?
Let’s say I reach out and touch your arm. How do you feel it?

This sensation begins with receptors located in your skin, called mechanoreceptors. Remember
This sensation begins with receptors located in your skin, called mechanoreceptors. Remember

in our episode about the auditory system, we talked about the way that hair cells are
in our episode about the auditory system, we talked about the way that hair cells are

activated by movement?
activated by movement?

The mechanoreceptors in your skin are similar - they respond to pressure, or distortion.
The mechanoreceptors in your skin are similar - they respond to pressure, or distortion.

We have four major types of mechanoreceptors scattered across our hairless skin, such as
We have four major types of mechanoreceptors scattered across our hairless skin, such as

the skin on your fingers and lips, and they all have pretty funny names.
the skin on your fingers and lips, and they all have pretty funny names.

Meissner’s corpuscles, or tactile corpuscles, respond to light touch and vibrations. These
Meissner’s corpuscles, or tactile corpuscles, respond to light touch and vibrations. These

are very sensitive receptors, for fine touch discrimination.
are very sensitive receptors, for fine touch discrimination.

Ruffini endings, or bulbous corpuscles, are located deeper in your skin and in the connective
Ruffini endings, or bulbous corpuscles, are located deeper in your skin and in the connective

tissues of the body, and respond to skin stretch and angle change in your joints.
tissues of the body, and respond to skin stretch and angle change in your joints.

Merkel nerve endings, or Merkel discs, help us detect ongoing pressure, like a hand holding
Merkel nerve endings, or Merkel discs, help us detect ongoing pressure, like a hand holding

yours.
yours.

Lamellar corpuscles, or Pascinian corpuscles, are highly sensitive to vibration.
Lamellar corpuscles, or Pascinian corpuscles, are highly sensitive to vibration.

These receptors respond to sudden changes or disturbances, and are probably useful for
These receptors respond to sudden changes or disturbances, and are probably useful for

distinguishing changes in texture.
distinguishing changes in texture.

No matter which kind of receptor they are, they’re located at the ends of afferent
No matter which kind of receptor they are, they’re located at the ends of afferent

nerve fibers - that is, nerve cells located in the periphery of the body.
nerve fibers - that is, nerve cells located in the periphery of the body.

The nerves transmitting the sensation have their cell bodies in structures called the
The nerves transmitting the sensation have their cell bodies in structures called the

dorsal root ganglia, or DRGs.
dorsal root ganglia, or DRGs.

The DRGs are located along the outside of your spinal column, and are essentially “bundles”
The DRGs are located along the outside of your spinal column, and are essentially “bundles”

of cells, collecting all of the nerve fibers into one structure before projecting the signal
of cells, collecting all of the nerve fibers into one structure before projecting the signal

on to the spinal cord.
on to the spinal cord.

The cells in the spinal cord receive the signal and then send projections across the midline
The cells in the spinal cord receive the signal and then send projections across the midline

(the middle of the body), and the signal actually gets sent to the opposite side of your brain
(the middle of the body), and the signal actually gets sent to the opposite side of your brain

from the side where you felt it - so if I touch your right hand, the sensation gets
from the side where you felt it - so if I touch your right hand, the sensation gets

passed to the left side of your brain for processing.
passed to the left side of your brain for processing.

The next stop is in the thalamus, acting as a relay for the sensory signals coming from
The next stop is in the thalamus, acting as a relay for the sensory signals coming from

your skin; finally, projections to the postcentral gyrus in the parietal lobe of your cortex
your skin; finally, projections to the postcentral gyrus in the parietal lobe of your cortex

create a map of your body.
create a map of your body.

By mapping all of the signals coming in from your skin to dedicated spots on your cortex,
By mapping all of the signals coming in from your skin to dedicated spots on your cortex,

your brain is able to tell you exactly where you felt a given sensation.
your brain is able to tell you exactly where you felt a given sensation.

Of course, pressure and vibration aren’t the only senses you detect with touch, right?
Of course, pressure and vibration aren’t the only senses you detect with touch, right?

Our skin is also able to sense temperature and, obviously, pain. So how can we tell if
Our skin is also able to sense temperature and, obviously, pain. So how can we tell if

something is hot or cold, or if a pinch feels uncomfortable?
something is hot or cold, or if a pinch feels uncomfortable?

The trick is in the receptor.
The trick is in the receptor.

Our ability to sense temperature is still something of a mystery. Scientists think that
Our ability to sense temperature is still something of a mystery. Scientists think that

different types of nerve fibers are responsible for hot and cold sensation.
different types of nerve fibers are responsible for hot and cold sensation.

There’s also some evidence that a particular family of proteins, called Transient receptor
There’s also some evidence that a particular family of proteins, called Transient receptor

potential or TRP channels, might play a role - and they’re connected to other types of
potential or TRP channels, might play a role - and they’re connected to other types of

“hot” and “cold” we experience too
“hot” and “cold” we experience too

For example, TRPV1 (V for “vanilloid”) channels respond to capsacin - the chemical
For example, TRPV1 (V for “vanilloid”) channels respond to capsacin - the chemical

that makes jalapeños spicy.
that makes jalapeños spicy.

Another type of TRP channel, TRPM8, responds to menthol, a chemical that is found naturally
Another type of TRP channel, TRPM8, responds to menthol, a chemical that is found naturally

in peppermint that produces a “cooling” sensation.
in peppermint that produces a “cooling” sensation.

Pain is a different animal.
Pain is a different animal.

Here, I’m talking just about “nociceptive”, or peripheral pain, which you sense in response
Here, I’m talking just about “nociceptive”, or peripheral pain, which you sense in response

to harmful stimuli.
to harmful stimuli.

To detect pain, your nerves use specialized cells called nociceptors.
To detect pain, your nerves use specialized cells called nociceptors.

These nerve fibers use temperature, pressure, and chemical stimuli to determine if something
These nerve fibers use temperature, pressure, and chemical stimuli to determine if something

is painful or not.
is painful or not.

These receptors can be found in your skin, joints, and on some of your internal organs.
These receptors can be found in your skin, joints, and on some of your internal organs.

Nociceptors are essentially just nerve endings embedded in your skin, like the roots of a plant
Nociceptors are essentially just nerve endings embedded in your skin, like the roots of a plant

Let’s say you’ve just gotten a paper cut (ouch!).
Let’s say you’ve just gotten a paper cut (ouch!).

There are three sorts of pain sensation associated with that - first, without thinking, you jerk
There are three sorts of pain sensation associated with that - first, without thinking, you jerk

your finger away.
your finger away.

This is the result of a reflex arc, wherein a sensory neuron registers the painful stimuli
This is the result of a reflex arc, wherein a sensory neuron registers the painful stimuli

and passes it along to your spinal cord.
and passes it along to your spinal cord.

In the reflex response, the information doesn’t get processed by your brain; instead, it’s
In the reflex response, the information doesn’t get processed by your brain; instead, it’s

passed right back out of your spinal cord via motor neurons that control your movement,
passed right back out of your spinal cord via motor neurons that control your movement,

causing your hand to jerk back.
causing your hand to jerk back.

Next, you feel the first conscious “sharp” sensation of pain, as fast signaling nerves
Next, you feel the first conscious “sharp” sensation of pain, as fast signaling nerves

called A-delta fibers, respond, passing the signal to synapses with neurons in your spinal cord.
called A-delta fibers, respond, passing the signal to synapses with neurons in your spinal cord.

Like mechanical stimuli, this signal gets passed up to the somatosensory cortex, allowing
Like mechanical stimuli, this signal gets passed up to the somatosensory cortex, allowing

you to consciously pinpoint the location of the pain (Ah! My finger!).
you to consciously pinpoint the location of the pain (Ah! My finger!).

These fibers only react to mechanical and temperature stimuli, but not chemical, which
These fibers only react to mechanical and temperature stimuli, but not chemical, which

might explain why you don’t always feel the burn of lemon juice in a cut right away!
might explain why you don’t always feel the burn of lemon juice in a cut right away!

Other nerve fibers, called C-fibers, react more slowly, passing along the deeper, aching pain
Other nerve fibers, called C-fibers, react more slowly, passing along the deeper, aching pain

These cells project to the spinal cord as well, though they synapse with a slightly
These cells project to the spinal cord as well, though they synapse with a slightly

different set of spinal cord neurons, which project to the brainstem and the thalamus.
different set of spinal cord neurons, which project to the brainstem and the thalamus.

Pain, temperature, and touch are all important for helping us to navigate in the world.
Pain, temperature, and touch are all important for helping us to navigate in the world.

We’re still learning a great deal every day about how the body processes these sensations.
We’re still learning a great deal every day about how the body processes these sensations.

One thing we know for certain - your senses are all important for helping you develop
One thing we know for certain - your senses are all important for helping you develop

a rich and complete perception of the world around you.
a rich and complete perception of the world around you.

Our sensory systems are vital to letting us move through and interact with our environment,
Our sensory systems are vital to letting us move through and interact with our environment,

and better understanding our senses will allow scientists and doctors to develop new treatments
and better understanding our senses will allow scientists and doctors to develop new treatments

for patients struggling with incomplete or damaged sensory systems.
for patients struggling with incomplete or damaged sensory systems.

In a future video, we might talk about some advances being made in this arena - let me
In a future video, we might talk about some advances being made in this arena - let me

know in the comments or on Twitter if this is a topic you’re interested in hearing more about
know in the comments or on Twitter if this is a topic you’re interested in hearing more about

So what does our brain do next with all of this sensory information coming in? How do
So what does our brain do next with all of this sensory information coming in? How do

we use that information? Now that we’ve finished covering the senses, we’ll start
we use that information? Now that we’ve finished covering the senses, we’ll start

to explore more topics to answer these questions.
to explore more topics to answer these questions.

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Thanks for watching! If you liked this video, give it a thumbs up and hit subscribe to become

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I’m Alie Astrocyte, and until our next transmission, over and out!
I’m Alie Astrocyte, and until our next transmission, over and out!