Balance
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How does your body maintain a sense of balance?
As if our ears couldn’t get any more interesting, they also have an important role to play in our balance, moving our head and understanding our movement through space.
The vestibular system, or system of balance, is an amazing sensory system located in our ears, that is responsible for some very important tasks.
Perhaps not an obvious sense to record – unless thinking about the properties of a gravity-defying sculpture – using this sense to understand and communicate collections can provide new insights into what they can offer.
We can think about it in terms of:
- how we balance – keeping the head balanced to ensure a priceless crown doesn’t slip off
- how collections balance – whether a child’s doll needs a mount to stay upright in a case
- how subjects in an item balance – a photograph of Maria Spelterini tightrope walking across Niagara gorge
A complex sense, balance it is best understood in combination with its other important sensory counterparts – follow on for more.
The role of your vestibular (or system of balance) changes when we undertake different tasks, so how you use the term may be different depending on the context.
Let’s take a focused look at the vestibular system in isolation.
Watch the videos and/or read the transcripts below.
Transcript
Vestibular actually refers to the space in the inner ear in which the Vestibular Labyrinth is located, called the Vestibule, like the vestibule in an old-fashioned home.
The vestibular system is the sensory system with its receptors located in the inner ear, but which are hidden from sight so you can’t see them by looking into the ear.
The vestibular system is a little bit mysterious, but its role is to tell your brain about head movement:
- how far
- how fast
- what direction you’re moving your head
You use that information to help maintain your balance to generate some eye movement so that you can see clearly while you’re moving around.
- As you walk around the world, your head bobs a little bit on your flexible neck.
- You don’t realise it, but your eyes move in in the opposite direction to counteract that head movement so you continue to see clearly.
- You also use information from your vestibular system to tell you if you’re moving or if you’re not moving Therefore to give you your conscious sense of spatial orientation.
- For example gymnasts and acrobats use that sense to tell them when they’ve done a turn in the air, when they’ve stopped turning, when they’ve hit the ground again.
You use that information about head movement to help modulate some of your autonomic nervous system responses such as your:
- heart rate
- breathing
- stomach motility
- sweating
- when you’re engaged in any kind of motion activity
Vestibular systems of other animals
- Crabs have vestibular systems, goldfish have vestibular systems, sharks have rather primitive vestibular systems, but they work pretty well for them.
- So most animals above the level of insects have vestibular systems.
- A curious fact is that the size of the Vestibular Labyrinth in the inner ear doesn’t change very much, depending on the head size.
- It turns out that the coefficient of variation, in other words the change in size, is only about 10%.
- So a mouse which has a very tiny head has a Vestibular Labyrinth that’s almost the same size as yours, and a whale which has a very big head has a Vestibular Labyrinth that’s also almost the same size as yours.
Transcript
The vestibular system is a sensory system responsible for providing our brain with information about:
- motion
- head position
- spatial orientation
- It also is involved with motor functions that allow us to:
- keep our balance
- stabilise our head and body during movement
- maintain posture
The main components of the vestibular system are found in the inner ear in a system of compartments called the vestibular labyrinth, which is continuous with the cochlea.
- The vestibular labyrinth contains the semi-circular canals which are three tubes that are each situated in a plane in which the head can rotate.
- Each of the canals can detect one of the following head movements: nodding up and down, shaking side to side, or tilting left and right.
- The semi-circular canals are filled with a fluid called endolymph.
- When the head is rotated, it causes the movement of endolymph through the canal that corresponds to the plane of the movement.
- The endolymph flows into an expansion of the canal called the ampulla, within which there are hair cells, the sensory receptors of the vestibular system.
- At the top of each hair cell is a collection of small ‘hairs’ called stereocilia.
- The movement of the endolymph causes movement of these stereocilia, which leads to the the release of neurotransmitters to send information about the plane of movement to the brain.
- The vestibular system uses two other organs, known as the Otolith organs, to detect forward and backward movements and gravitational forces.
There are two otolith organs in the vestibular labyrinth:
- the utricle, which detects movement in the horizontal plane.
- the saccule, which detects movement in the vertical plane.
- Within the utricle and saccule, hair cells detect movement when crystals of calcium carbonate called otoconia, shift in response to it, leading to movement in the layers below the otoconia and displacement of hair cells.
In relation to the vestibular system more specifically, the following terminology will serve as a reminder as to how balance aligns with bodily functions and actions.
Functions
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Postural responses (Vestibulo-Spinal Reflex)
- Keeps the body upright and prevent falls when the body is unexpectedly knocked off balance.
Ocular-motor responses (Vestibulo-Ocular Reflex)
- Keeps the eyes steadily focused while the head is in motion.
Visceral responses (Vestibulo-Colic Reflex)
- Keeps the head and neck centred, steady, and upright on the shoulders.
Links to other sensory systems
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As noted above, many sensory systems provide support the body’s equilibrium and maintains balance.
- Somatosensory / Proprioceptive System
- Vestibular System
- Visual System
Balance
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- The ability to maintain a line of gravity within a ‘base of support’ – linked to centre of gravity and a stable base e.g. feet on the ground.
- The ability to maintain equilibrium – equilibrium defined as any condition in which all acting forces are cancelled by each other resulting in a stable balanced system.
Static Balance
- The ability to maintain a fixed posture, and maintain postural stability and orientation with the centre of mass over the base of support at rest.
Dynamic Balance
- The ability to transfer the vertical projection of the centre of gravity around the supporting base of support, and maintain postural stability and orientation with the centre of mass over the base of support while in motion.
Centre of gravity/mass
- The centre of gravity, or balance point, of an object is where it will balance and be stable if supported.
- If the object is not supported directly below its centre of mass, it will be unstable and fall over.
Contact area
- Objects with larger, flatter surfaces in contact with the ground are easier to balance because their centre of gravity is usually within that area.
- Objects with thin edges, points, or round surfaces have smaller contact areas with the ground, making them more difficult to balance
Height
- Tall objects have a higher centre of mass, so they fall more slowly, giving you more time to correct your body to keep them upright.
Visual cues
- When balancing an object, it’s easier to watch the top of the object because it moves around in a wider arc, giving you more visual clues to help keep it upright.
Synonyms for balance
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- Postural control
- Postural stability
- Equilibrium
Balance can include that of the self and body as well as of the things around us.
For example, do you have a ‘gravity defying’ sculpture, circus apparatus or a manual set of scales for weighing flour.
To understand this, here are a couple of exercises you can try.
NB Please only undertake these exercises where and when you will be safe. Do not do them if you have any pre-existing balance conditions, or other sensory processing differences, meaning they may cause you harm.
Bodily balance
Where safe and comfortable to do so, balance your body in 4 ways:
- Stood on a solid floor (in the office)
- Stood on an uneven surface (rocky carpark)
- Sat with your feet touching the floor (desk chair)
- Lay down (at home in bed, or on a sofa)
Think about the following things:
- Where is your centre of gravity (the bit that gives you most stability)?
- Is it a small area (balls of your feet) or large area (the whole back side of your body)?
- What parts of your body of you body are moving, if any, as you try to maintain balance?
- What parts of your body are you providing strength to, if any, to maintain balance?
- How often do you have to reposition yourself to maintain balance?
- Does your head move around in this position? if so, how?
- Do you need your eyes open to maintain balance?
- Is maintaining balance disorientating you?
- (If stood up) How does your balance change as you walk across this surface?
- Can you maintain a strong posture in this position (upright, straight back)?
- How does it make you feel to balance your body in this way?
Balance of ‘things’
Choose some items around you that are safe to handle and move into different positions, and unlikely to break if dropped (e.g. pencil, ruler, stack of post-it notes, sticky tape roll).
Try the following exercises by placing the items on a different point of contact (e.g. ruler lying flat, then balancing on it’s slender side).
- Where is the centre of gravity (the bit that gives it stability)?
- Is it a small area (the point of a pencil) or large area (a piece of paper lay flat)?
- Does it balance by itself (it doesn’t ‘fall over’)?
- Do you need to put in a lot of assistance and tweak it to find it’s balance?
- Does it maintain balance on different surface types (flat desk, packet of crisps, on water)?
- How do you feel when observing and intervening in the balance of this item?
Want to learn a little more about vertigo?
Zero to Finals ‘Understanding the Causes of Vertigo’ (live transcript available on YouTube)
Or motion sickness?
Ted-Ed ‘The mystery of motion sickness’ – Rose Eveleth (live transcript available on YouTube)