Balance Part 2: The Three Balance Systems

Welcome to the second blog post in our three part series on balance. In our last post we discussed the basics of balance including what Balance and Coordination are, how detailed and dynamic balance must be, and we saw some examples of what can go wrong when our balance system fails to function correctly. In this post we will look at the three systems of balance so that in our final post of the series we can explore how they communicate and where problem may come from.

As we described in our Balance Basics post, it is vital for our brain to determine where we are in space. It is so important that our body has three separate systems These systems allow us to have a wide range of information, but it also provides redundancy. Each system has a slightly different specialty in the type of information it provides and the area of the body that it tells us about, but they overlap quite a bit to ensure that if one system is compromised or lost, we can still function to a certain degree.

The first system is our eyes, our Visual System. In the vast majority of people, this system is the one that our brain relies on the most. We are able to see this quite easily when we ask someone to close their eyes while standing with their heels and toes together. Most everyone will have at least some sway of their body as they work to maintain balance, but there are many who may lose their balance and may even fall over. Even those who consider themselves to be quite stable can notice a difference when standing on one foot and closing their eyes. Feel free to try either of these simple tests, but please be safe and place yourself near a wall or furniture you can grab onto to prevent you from falling. Falls are a common cause of injury and death, especially in older populations and I would not want anyone to get hurt.

The eyes themselves grant us a very large amount of information. They pick up details that we rarely think of, but details that make a big difference for our brain. Our eyes tell us how close the horizon or ground is to level, if we are rotating forward, backward, or to the sides, and it even tells us when we are getting closer and farther from objects. These are just three things that the brain considers, but there are many more. Our brain strives to keep our eyes level to the horizon and will sacrifice other things to make it happen. Without the feedback from our visual system, our brain must rely on the other two systems in order to determine what is happening.

The second system is the inner ear. This system is called the Vestibular System. The vestibular system is just as complex as the visual system, but it measures different things. Our eyes may allow us to see our limbs moving, and measure our relation to the world around us, but because the vestibular system is located in the inner ear, it is only able to measure the movement of our heads through space. The vestibular apparatus itself (the complex group of receptors) tells us if we are rotating our heads left, right, up, down, tilting our heads to the left or right, and all the angles in between. It also tells us if we are moving in a straight line forward, backward, left, right, up, or down. On top of a difference in what it measures, the vestibular system has another little feature that our eyes don’t. It is able to adapt to constant movement. This may sound a little complicated, but imagine this. You are sitting in your car at a stoplight. You feel no movement because you are not moving. When the light turns green, you press the gas pedal and the car begins to move forward, increasing speed as you accelerate. You feel this change in speed through the inner ear (and also through your eyes and the force of your body against the seat, but let’s keep it focused on the vestibular system). When you reach your cruising speed and stop accelerating, your vestibular system adapts and you no longer feel like you are moving. Now, if we were to slow the car back down or make a turn, you would be able to feel the change in your speed or the rotation of the car, but once you regain a constant speed in a straight direction, the system once again adapts and quiets down.

The third system of balance is the Proprioceptive System. This system’s name is quite a mouth full but is pronounced pro-pree-oh-sep-tiv. The proprioceptive system is information from all over our body. This information includes how long or short muscles are, how quickly our muscles are moving, the angles of joints, and even the tensions on different tissues and skin. This system definitely contains the greatest number of receptors from the largest area. We see this system at work when we look at the example of our drunk test from the last blog post. As the officer asks you to close your eyes and touch your nose with your finger, your brain is constantly measuring the where your limbs are in space, if you are having to push more into your toes to keep from falling forward, if your head is straight or turned, and so many other factors that we couldn’t list them all here. This feedback from the body is super important for fine-tuning the movements we make in our every day lives, but it becomes much more important when we are dealing with fine detail activities like hand-eye coordination and reaction reflexes in professional athletes.

While the three systems of balance all measure different things, they are all working toward one common goal: creating a map of where our body is in space so that we can stay upright against gravity and carry out the activities that allow us to stay alive. These three systems must all tell the brain what they experience and it is the brain’s job to match up all the information and create that final idea of where we are. In our next blog post we are going to look at the last aspect of balance: what happens when we get conflicting information from the three systems and what can we do to correct the problems and restore balance to our bodies. For more information or for any specific inquiries, please contact us.

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