Equilibrioception or
sense of balance In biomechanics, balance is an ability to maintain the center of gravity of a body within the base of support with minimal postural sway. When exercising the ability to balance, one is said to be balancing....
is one of the
physiologicalPhysiology is the science of the functioning of living systems. It is a subcategory of biology...
senseSenses are the physiological methods of perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...
s. It helps prevent
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s and
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
s from falling over when
walkingWalking is the main form of animal locomotion on land, distinguished from running and crawling. When carried out in shallow waters, it is usually described as wading and when performed over a steeply rising object or an obstacle it becomes scrambling or climbing...
or standing still.
Normal balance functioning
Balance is the result of a number of body systems working together. Specifically, in order to achieve balance the eyes (visual system), ears (vestibular system) and the body's sense of where it is in space (proprioception) ideally need to be intact. Also the brain, which compiles this information, needs to be functioning normally.
The semicircular canals, found within the vestibular apparatus, let us know when we are in a rotary (circular) motion. The semicircular canals are fluid-filled. Motion of the fluid tells us if we are moving. The vestibule is the region of the inner ear where the semicircular canals converge, close to the
cochleaThe cochlea is the auditory portion of the inner ear. Its core component is the Organ of Corti, the sensory organ of hearing, which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea....
(the hearing organ). The vestibular system works with the visual system to keep objects in focus when the head is moving. This is called the vestibulo-ocular reflex (VOR).
Movement of fluid in the semicircular canals signals the brain about the direction and speed of rotation of the head - for example, whether we are nodding our head up and down or looking from right to left. Each semicircular canal has a bulbed end, or enlarged portion, that contains hair cells. Rotation of the head causes a flow of fluid, which in turn causes displacement of the top portion of the hair cells that are embedded in the jelly-like cupula. Two other organs that are part of the vestibular system are the utricle and saccule. These are called the otolithic organs and are responsible for detecting linear acceleration, or movement in a straight line. The hair cells of the otolithic organs are blanketed with a jelly-like layer studded with tiny calcium stones called otoconia. When the head is tilted or the body position is changed with respect to gravity, the displacement of the stones causes the hair cells to bend.
The balance system works with the visual and skeletal systems (the muscles and joints and their sensors) to maintain orientation or balance. For example, visual signals are sent to the brain about the body's position in relation to its surroundings. These signals are processed by the brain, and compared to information from the vestibular, visual and the skeletal systems.
In humans
In humans, equilibrioception is mainly sensed by the detection of acceleration, which occurs in the
vestibular systemThe vestibular system, which contributes to our balance and our sense of spatial orientation, is the sensory system that provides the dominant input about movement and equilibrioception. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear,...
. Other senses play roles as well, e.g. the
visual systemThe visual system is the part of the central nervous system which enables organisms to see.It interprets the information from visible light to build a representation of the world surrounding the body...
and
proprioceptionProprioception is the sense of the relative position of neighbouring parts of the body...
. The importance of visual input for balance is illustrated by its being harder to stand on one foot with eyes closed than with eyes open.
The sense of balance, usually, deteriorates in the process of aging of a person. However, it can be improved considerably with the help of special training.
Vestibular system
In the vestibular system, equilibrioception is determined by the level of
fluidA fluid is a substance that continually deforms under an applied shear stress. All gases are fluids, but not all liquids are fluids. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
properly called
endolymphEndolymph is the fluid contained in the membranous labyrinth of the inner ear.It is also called Scarpa's fluid, after Antonio Scarpa.-Composition:...
in the
labyrinthThe labyrinth is a system of fluid passages in the inner ear, including both the cochlea, which is part of the auditory system, and the vestibular system, which provides the sense of balance...
- a complex set of tubing in the inner
earThe ear is the organ that detects sound. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species. It not only acts as a receiver for sound, but plays a major role in the sense of balance and body position...
.
Dysfunction
When the sense of balance is interrupted it causes dizziness, disorientation and
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
. Balance can be upset by
Meniere's diseaseMénière's disease is a disorder of the inner ear that can affect hearing and balance. It is characterized by episodes of dizziness and tinnitus and progressive hearing loss, usually in one ear. It is caused by lymphatic channel dilation, affecting the drainage of endolymph...
,
superior canal dehiscence syndromeSuperior canal dehiscence syndrome is a rare medical condition of the inner ear, first described in 1998 by of Johns Hopkins University Hospital, Baltimore, USA, leading to hearing and balance disorders in those affected....
, an inner ear infection, by a bad
common coldAcute viral rhinopharyngitis, or acute coryza, known as an upper respiratory virus, or commonly called a cold, is a contagious, viral infectious disease of the upper respiratory system, primarily caused by rhinoviruses, or coronaviruses...
affecting the head or a number of other medical conditions. It can also be temporarily disturbed by quick or prolonged acceleration, for example riding on a merry-go-round. See also
vertigoVertigo is a specific type of dizziness, a major symptom of a balance disorder. It is the sensation of spinning or swaying while the body is actually stationary with respect to the surroundings.The effects of vertigo may be slight...
. Blows to the head can also affect equilibrioreception, especially those to the side of the head or directly to the ear.
Most
astronautAn astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....
s find that their sense of balance is impaired when in orbit because they are in a constant state of
weightlessnessWeightlessness is a phenomenon experienced by people during free-fall. Although the term zero gravity is often used as a synonym, weightlessness in orbit is not the result of the force of gravity being eliminated or even significantly reduced...
. This causes a form of
motion sicknessMotion sickness or kinetosis, also known as Travel Sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement...
called
space adaptation syndromeSpace adaptation syndrome or space sickness is a condition experienced by around half of space travelers during adaptation to microgravity. It is related to motion sickness, as the vestibular system adapts to weightlessness....
.
In animals
Some animals have better equilibrioception than humans, for example a
catThe cat , also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small carnivorous mammal that is valued by humans for its companionship and its ability to hunt vermin and household pests...
uses its
inner earThe inner ear is the bony labyrinth, a system of passages comprising two main functional parts:* The cochlea is the hearing part of the inner ear.* The semicircular canals , the utricle and the saccule are the balance part of the inner ear...
and tail to walk on a thin
fenceA fence is a freestanding structure designed to restrict or prevent movement across a boundary. It is generally distinguished from a wall by the lightness of its construction: a wall is usually restricted to such barriers made from solid brick or concrete, blocking vision as well as passage .Fences...
.
http://www.sciencedaily.com/articles/e/equilibrioception.htm
Equilibrioception in many marine animals is done with an entirely different organ, the
statocystThe statocyst is a balance organ present in some aquatic invertebrates . It consists of a sac-like structure containing a mineralised mass and numerous innervated sensory hairs . The statolith possesses inertia, causing the mass to move when accelerated...
, which detects the position of tiny calcareous stones to determine which way is "up".
Training devices
- balance ball
- balance board
A balance board is a device used for recreation, athletic training, brain development, therapy, musical training and other kinds of personal development. It is a lever similar to a see-saw that the user usually stands on, usually with the left and right foot at opposite ends of the board...
- balance bicycle
130 px|leftA balance bicycle is a training bicycle that helps the rider learn balance and steering. It has no pedals, no crankset and chain, and no training wheels. It can be a normal bicycle with pedals and related parts removed, or it can be purpose-built...
- BOSU
A BOSU Balance Trainer, or BOSU ball as it is often called, is an fitness training device, invented in 1999 by David Weck, consisting of an inflated rubber hemisphere attached to a rigid platform. It is also referred to as the "blue half-ball", because it looks like a stability ball cut in half...
- slackline
- tight rope
External links