Why do humans get "goosebumps?"
We're going to answer that question in today's video,
and even talk about what causes "goosebumps" by going over some of the relevant anatomy.
We'll take a look at real human skin, and even a real human brain
to discuss the brain's involvement in this phenomenon that we call, "goosebumps."
More importantly, do "goosebumps" do us any good? We're gonna have to compare ourselves to some of
our furry little cousins — the mammals — in order to answer that question.
So, let's do this!
Why the name "goosebumps?"
Well, when your skin raises up and creates those bumps
it resembles the skin of a goose when the feathers were plucked.
Those spots where the feathers were located have these little bumps or protrusions,
hence the name "goosebumps." Speaking of skin, let's take
a look at some real skin to discuss the relevant anatomy to these "goosebumps."
So, this is a dissection from the mid-back of a cadaver.
I'm probing the top layer of the skin and we refer to this layer as the Epidermis.
Now this is obviously the layer where we'd see the bumps,
or the "goosebumps" try to push into or create the protrusions.
But, we also need to talk about the second layer.
The second layer here — the majority of this cut edge — is referred to as the Dermis.
So, the paper thin top is the Epidermis but then the thicker portion here is the Dermal tissue.
Now the Dermal tissue is extremely relevant because it's going to
contain some very important structures that have to do with "goosebumps."
So, let's zoom into this area with our model.
Here is our anatomical model of the skin — a really zoomed-in version
of what we were looking at on the skin dissection just a second ago.
Let me just orient you to this model — from here to here is the Epidermis.
You can see some different colors and the Epidermis does have some sublayers associated
with it — that's for a different video. For our purposes,
here is the Epidermis and then from here to here is the Dermis, or the Dermal tissue.
This is where the majority of the magic is going to happen in our
"goosebumps" story, in the Dermal tissue.
We have to talk about the hairs because when we
get involved in "goosebumps" you talk about people's hair standing up, but,
"goosebumps" are going to be associated with these structures called Hair Follicles.
Here is the anatomy of a Hair Follicle.
FYI, "Follicle" just means "little bag."
Think of it as a little bag for hair to grow out of.
The Hair Follicle in the current state is at an angle that's less than 90 degrees.
They are slanting up like so, but, there is something extremely important that
is associated with these Hair Follicles that helps us understand "goosebumps."
That is this structure here, and this is actually a muscle called the Erector Pili muscle.
"Erector" just means it's going to "lift highly" — it refers to hair.
So take a look at this relationship here.
I've got a Hair Follicle slanted at this angle and I've got this Erector Pili muscle here.
You can see it attaches to the upper portion of the Dermis,
then down to the base of the Hair Follicle.
Now when this muscle contracts take a look — it'll contract and pull like so,
and when it pulls the base of the Follicle it goes
like so, [Jonathan makes sound effect] straightens the hair up and down.
It will also create a little bump or protrusion
kind of pushing up into the Dermal tissue because we're getting that swooping and kind of pushing
upward to create the "goosebumps." The hairs will stand up straight now.
One other really important point about this muscle called the Erector Pili Muscle,
is what we refer to as a smooth muscle.
There's different types of muscle tissue in the human body.
The muscles we're used to working out at the gym like the Biceps — that's a Skeletal Muscle.
We can voluntarily move those types of muscles whenever we want to.
But, Smooth Muscles like the one that we're seeing right here called the Erector Pili Muscle
are involuntary.
This means we can't choose to control them.
Now, I do think it would be pretty awesome if we could control
all the Erector Pili muscles whenever we wanted to.
Could you imagine if we could make
all your hair go up all at once? That would be pretty cool!
Unfortunately for nerds like me, that just doesn't occur.
So if "goosebumps" or in other words the activation of this Erector Pili muscle
are involuntary what causes it to occur?
Well typically this is activated through either a physiological stress such as
exposure to cold or even an emotional stress such as anger, fear, or other strong emotions.
There's this amazing structure in the brain that gets involved in regulating such emotions,
and that is this structure in the central core of the brain referred to as the Hypothalamus.
Just to orient you guys, you probably got an idea this is a
sagittal cut, or, midline cut through the brain.
Again, the Hypothalamus, located underneath my probe in the central core.
Now the Hypothalamus does a lot of things.
Like I said, involved in emotions,
also involved in Homeostasis. But it also gets involved
in regulating this part of the Autonomic Nervous System called the Sympathetic Nervous System.
Autonomic just refers to automatic involuntary control.
The Sympathetic Nervous System often gets nicknamed the “fight or flight” system because
it releases a Neurotransmitter or a chemical referred to as Noradrenaline or Norepinephrine.
Those are the same things, just a different name for the same chemical
that's closely related to Adrenaline or Epinephrine.
So let's take you through a little sequence, or, an example of this.
The Hypothalamus processing strong emotions or physiological
stress or distress creates a Sympathetic response,
the signal will essentially go down the spinal cord and make it to the Thoracic region,
and then send impulses out to nerves to go to specific targets throughout the body.
One of those specific targets being in the skin.
Here it would take this little nerve impulse here and release Norepinephrine
or Noradrenaline onto the receptors of this Erector Pili Muscle causing it to activate.
Boom, hair starts to stand up.
So let's just go a little bit further with that example.
All of us have been cold and then gotten "goosebumps."
Now when you got those "goosebumps" when you were cold, did you all of a sudden think,
“wow — these goosebumps have made me really warm”?
It just doesn't happen like that for us.
The reason is, we've lost a ton of hair when we compare ourselves to our ancestors
or some of our cousins such as the mammals, which are covered in a whole bunch of fur.
In that case, for them these "goosebump" muscles or Erector Pili muscles are essential.
Let me illustrate why that's so important for our furry little friends.
When the Erector Pili muscle contracts and the hairs start to stand up more upright
that creates these little pockets where dead or stagnant air starts to fill
and creates little pockets of stagnant air that's not moving around very much.
It’s one of the most efficient forms of insulation.
We do it all the time with a double pane window.
It’s much more efficient than a single pane window.
Pane, dead air space, and a second pane.
That really stops heat from leaving the home.
Same idea, when you have these little dead air spaces that are formed by all the fur
creating those little air pockets it really stops heat from leaving the body of the animal.
Now that takes care of the response to cold but what about this anger and fear response?
You've probably seen
a dog or a wolf or another ferocious creature get mad and show its teeth and snarl.
On a dog it almost looks like their spines popping out of their back.
That has nothing to do with their spine — we often refer to it as hackles,
but the fur from the Erector Pili Muscle starts to stand up
and that makes the animal look larger and more intimidating to keep enemies away.
Now again I think it'd be cool if we could do it although I don't really know if people
would be running for the hills if we also had our hair on our arm or our legs just pop
out like we're trying to scare somebody away, but it would still be nerdy and kind of cool.
So in other words, for us,
not much of a function for this Erector Pili Muscle or the creation of "goosebumps. "
It's kind of this
lost function that we lost through years and years and years of evolution and loss of hair.
Now we clothe ourselves and pack ourselves in houses and do other things to keep ourselves warm.
It also kind of explains those times where you might get "goosebumps" from other strong emotions.
For example, maybe you heard a song that you really liked and
those emote triggered emotional centers in your Hypothalamus.
Or maybe you watched this really inspiring anatomy video
and you all have Goosebumps because of everything we've just talked about.
If you want to have a greater understanding of the human body and how various structures,
such as muscles, nerves, blood vessels, and other things interact with each other,
it's best to kind of think of the human body as a puzzle or multiple puzzle pieces
interacting with each other to create this huge thing that we call the human body.
That's why I'm such a big fan of Brilliant.
Brilliant is a problem-solving website focused on math and science.
It teaches you to become a better problem solver through pattern recognition and use of logic.
Developing a scientific mind where you can ask the right questions,
critically think, analyze, and solve problems is one of the best skills that you can develop
Brilliant can help you to further develop these skills by diving deep into subject matter such as
engineering, chemistry, physics, and mathematics.
That can carry over into other subjects.
I always used to tell students, and still do, you want to learn how to learn
and wherever you learn and become better problem solvers in other subjects
it will carry over into things like anatomy, physiology, and other scientific topics.
So if you are interested in this go to brilliant.org/instituteofhumananatomy,
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