Imagine if it was pitch black in your room.
Would you be able to walk?
As long as nothing got in your way,
you'd probably be able to walk perfectly fine.
But why is this?
When walking in a pitch black room,
you rely on your sense of balance.
You know exactly where you are in space.
You know whether or not you're standing straight
up or if you're sitting down.
And as you're walking, you know if your right foot
is in front of your left or if your left foot
is in front of your right.
So how is it that we know exactly where our body is
in space without actually having a look at it?
Well, this is known as our sense of propioception.
And proprioception is basically defined as our ability
to sense exactly where our body is in space.
In other words, this is our sense of position.
And this sense actually originates
from a bunch of tiny little sensors that
are located throughout our entire body in almost all
of our muscles.
So let's imagine that this right here is a muscle in your leg
or in your arm.
Let's just say it's a muscle in your arm.
So there's a tiny little receptor in it,
inside of the muscle.
And this receptor will actually go up to your spinal cord
and then eventually to your brand.
And this receptor, if we kind of zoom in on it,
we zoom in on this receptor, is sensitive to stretching.
So as this muscle contracts, so if I
was going to lift something really heavy,
the muscle would contract, and it would get thinner,
so it would look like this.
It would get a bit thinner.
And so this sensor, which is known as a spindle--
I'll write that down here.
This is a spindle.
This sensor can sense that the muscle has been stretched out,
and it too will also stretch.
So it will go from this conformation
to this conformation.
It will actually get stretched out.
And so we can draw a little spring-like structure inside,
which is actually quite similar to what's
actually inside the spindle.
There's actually a protein inside that gets stretched.
When that protein gets stretched,
it fires a signal to the brain.
This is the basic principle behind proprioception.
So we're able to tell exactly how contracted
or how relaxed every single muscle is in our entire body,
and this allows us to know exactly where our body is
in space.
There's another word that's commonly
used to talk about your body's movements.
And this is known as kinesthesia.
So let me write that down-- kinesthesia.
And so if we talk about proprioception
to include your body's position in space
as well as your ability to balance,
so your sense of balance would be included
under proprioception, kinesthesia
is talking more about the movement of your body.
So one final way to differentiate between the two
is that proprioception can be thought
of as a cognitive awareness of your body in space.
So it's more cognitive.
So one way to think about this is
that it's a little bit more subconscious.
So you're not always thinking about exactly where your body
is in space, exactly how you're orientated, if you're walking,
or if you're running.
Your main concern isn't, oh, I hope-- it might be,
but your main concern isn't I hope
I'm not going to fall down.
Pretty much your sense of balance,
your sense of position, are pretty well
taken care of by your proprioceptive sense.
So it's more cognitive.
It's more something that's under the surface.
You're not overtly thinking about it.
On the other hand, kinesthesia is a little bit more
behavioral.
And what I mean by that is let's imagine
that you're playing golf or you're
trying to hit a baseball, constantly you're swinging.
Sometimes you miss, sometimes you hit the ball.
But every single time you actually swing the bat
or swing the golf club, your body
is able to detect exactly how it's moving.
And so over time, if you learn that, OK,
if I move in this certain direction,
I'm able to hit the golf ball, or if I move in this direction,
I'm able to hit the baseball, then
over time, your body is able to detect
exactly what that movement is and start
to undergo that movement more and more often.
So you're able to actually teach yourself
exactly how you should move in order to successfully complete
whatever task is at hand.
So that's just another way to distinguish between the two
terms.
But just keep in mind that proprioception and kinesthesia
are not the same.
So they are not the same.
So I'll draw a big x here.
But they do share a lot in common.
And what they do share in common is inferring movement,
and position, and where your body is in space.
And the big difference is, just to kind of summarize,
is that proprioception is concerned with position
while kinesthesia is concerned with movement.
And proprioception includes your sense of balance,
while kinesthesia does not.