Motion Sickness

Anatomy of Motion Sickness

Your brain is constantly gathering and analyzing data in terms of your body’s current orientation, movement, balance (i.e. equilibrium), and visual inputs. For example when you walk, your eyes, inner ear, and limbs all function in a coordinated fashion thanks to various inputs to your brain. Your brain recognizes everything it needs to in order to keep you upright and moving in the direction that you intend. Thankfully, all of this input and response in terms of spatial orientation is done at a subconscious level. Unfortunately, the cause of motion sickness occurs when there is a disconnect between what your eyes are seeing (visual receptors), what your balance and equilibrium is telling you (vestibular system), and what your body’s orientation (proprioceptors) is.

Your Vestibular System (Inner Ear)

Your inner ear (medically known as your vestibular system), deals with your body’s balance and position and is, most likely, the most important factor when it comes to experiencing motion sickness. The vestibular system is an amazingly complex combination of nerves and fluid filled channels within your inner ear. Your vestibular system helps to determine:

  • Whether you are moving forward and backward (such as walking).
  • Whether you are accelerating or decelerating (such as when you are in a car when someone stomps the gas or slams on the brakes).
  • Whether you are turning from one side to the other (such as when an airplane banks from one side to the other).
  • Whether you are moving upwards or downwards (such as climbing or descending stairs).
  • Whether you feel the effects of gravity or not (which you experience while riding in an elevator).

Your inner ear also helps to control your sense of balance (i.e. Equilibrium) and motion. It sends information to your brain that tells the other parts of your body whether they should compensate for the movements that you are experiencing in order to maintain a proper equilibrium.

Visual Receptors (Eyes)

The second component when it comes to determining where your body is at and whether it is experiencing motion are your eyes. The eyes help your brain determine where your body is spatially located in relation to the objects around it. Your eyes can also tell your brain:

  • Whether you are lying down or standing up (typically the objects around you will tend to remain motionless).
  • Whether your body is oriented right side up or upside down (such as when you are on a corkscrewing roller coaster).
  • Whether your body is leaning from one side or to the other (such as when you are standing perpendicular to the slope of a hill).

Whether you are moving forward or backward (such as when you look out the window of a train and the stationary objects around you appear to be moving by).

Proprioceptors (Proprioception)

The third component which helps your body determine whether it is at rest or in motion are your proprioceptors. Proprioceptors is just a fancy way of describing the various sensors that are located in your skin, joints, and muscles that tell your brain how your limbs and body are positioned. Your brain constantly takes in all the information that it receives from your eyes and from your vestibular system. In order to maintain proper balance and to initiate movement, your brain then takes all the data that it receives and unconsciously tells you joints, muscles, tendons, and ligaments to move accordingly. In addition, proprioceptors determine how our body’s are oriented based upon what parts of our body’s are touching the ground at the time.