We’ve all heard that old line about how we have five senses:
sight, sound, smell, taste, and touch.
That’s been truth since the ancient Greeks and Aristotle.
Our sensory systems are important for helping us navigate the world around us.
But wait one minute! What if I told you that you’ve got a secret superpower?
Like Spiderman, you have a sixth sense - your sense of *proprioception*.
The word “proprioception” comes from Latin words that translate to “one’s own grasp”.
Proprioception is your sense of the relative positions of your body parts
and the effort being put into movement. It’s how I know that my hand is just over here
to my left, even though I’m not looking at it, and how I can feel the effort of pulling
this weed out of the ground.
When I put it that way, it probably seems obvious that you have this sense, right?
How else would you be able to catch a ball when it’s tossed to you, and know exactly
how much effort your catch would take? But it turns out that this is a pretty complex
sensory system, and we’re still learning how it works!
It all began in 1906 with a man named Charles Scott Sherrington.
He introduced the idea of a “proprioceptor”, something inside you that would take information
about the movement of your body from muscles, tendons, and joints, and send it to your brain.
Scientists were so excited about the idea that they began a hunt for that structure.
This led to scientists discovering muscle spindles.
Muscle spindles are specialized nerve endings found
throughout your muscles, and they respond to changes in muscle length and the speed
at which muscle length changes, providing your brain with information about the position
of your limb and its movement. These spindles consist of fibers embedded within your muscles,
where they are contacted by cells called sensory neurons. These neurons pass the information
on to your spinal cord, where the information is passed up to your brain by other neurons.
But wait, there’s more! Your brain also uses information from cutaneous mechanoreceptors.
Cutaneous whaaa?! These are receptors in your skin, which respond to stretch, pressure,
and vibration which help with sensing joint position and movement. Another helpful structure
includes Golgi tendon organs, which are located in your tendons. These guys convey details
about muscle tension, which translates to your sense of exertion. Finally, information
also comes from the vestibular system of your inner ear, providing details about your spatial
orientation and balance.
Okay, so we have all of these structures shooting information to our brain, but how do we make
sense of it? We’re still learning about how the brain processes all of this input,
but we know that a lot of the information goes to the cerebellum, the piece of your
brain that looks a bit like a pile of spaghetti. The cerebellum is very important for regulating
movement and balance, especially when it comes to coordination and precise timing of movements.
Scientists believe that your brain combines this input directly from your limbs with other
sources of information, like your visual perception of your body and the space around you. Put
it all together, and you’ve got proprioception, baby!
So why is it important for us to understand proprioception? Well, it’s obviously pretty
essential for everyday life. Because of proprioception, we can move without looking - imagine being
in a dark room. Uh, hello? Whew. Thanks! Without proprioception, you can’t move because
you can’t see your feet! You can also train your proprioceptive sense to get stronger
and faster - just like Spider Man learning to use his new Spidey-sense, you hone your
proprioceptive skills whenever you practice hand-eye coordination. Proprioception is what
allows you to learn to drive a car, paint a picture, play video games, and type quickly
on the computer!
But want to learn something REALLY cool about your super power? Your proprioceptive sense
can be tricked! You can try it yourself at home with a little test called the “Pinocchio
Illusion”. To do it, place one finger on your nose. Then, have a friend
take something that vibrates, like an electric toothbrush or a
cell phone, and place it on your bicep tendon
The vibrating sensation
will trick your muscle spindles into thinking they’re stretching out, making it feel like
your arm is moving away from your face. Since you’re still touching your nose, those signals
tell your brain that your nose must be growing!
Thank you, friend!
As you can tell, proprioception is a tricky sense, but it’s a very important one! We’re
still trying to understand how the brain processes and synthesizes all of this information. And
just like so many super powers, the origin of this one is something of a mystery - but
maybe someday you can be a superhero and help uncover the answers to proprioception!