The sense of balance or equilibrioception is the
perception
Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
of
balance
Balance or balancing may refer to:
Common meanings
* Balance (ability) in biomechanics
* Balance (accounting)
* Balance or weighing scale
* Balance as in equality or equilibrium
Arts and entertainment Film
* ''Balance'' (1983 film), a Bulgaria ...
and
spatial orientation
In geometry, the orientation, angular position, attitude, bearing, or direction of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it occupies.
More specifically, it refers to the imagin ...
.
It helps prevent
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s and nonhuman
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s from falling over when standing or moving. Equilibrioception is the result of a number of
sensory systems
The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain invo ...
working together; the eyes (
visual system
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
), the inner ears (
vestibular system
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
), and the body's sense of where it is in space (
proprioception
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
) ideally need to be intact.
The vestibular system, the region of the inner ear where three semicircular canals converge, works with the visual system to keep objects in focus when the head is moving. This is called the
vestibulo-ocular reflex (VOR). The balance system works with the visual and
skeletal system
A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
s (the muscles and joints and their sensors) to maintain orientation or balance. Visual signals sent to the
brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
about the body's position in relation to its surroundings are processed by the brain and compared to information from the vestibular and skeletal systems.
Vestibular system
In the vestibular system, equilibrioception is determined by the level of a
fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
called
endolymph
Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. I ...
in the
labyrinth
In Greek mythology, the Labyrinth (, ) was an elaborate, confusing structure designed and built by the legendary artificer Daedalus for King Minos of Crete at Knossos. Its function was to hold the Minotaur, the monster eventually killed by the ...
, a complex set of tubing in the inner ear.
Dysfunction
When the sense of balance is interrupted it causes
dizziness
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Dizziness is a common medical c ...
,
disorientation
Orientation is a function of the mind involving awareness of three dimensions: time, Location (geography), place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to Substance int ...
and
nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
. Balance can be upset by
Ménière's disease
Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initial ...
,
superior canal dehiscence syndrome
Superior semicircular canal dehiscence syndrome is a set of hearing and balance symptoms, related to a rare medical condition of the inner ear, known as ''superior canal dehiscence''. The symptoms are caused by a thinning or complete absence of ...
, an
inner ear infection
Labyrinthitis is inflammation of the labyrinth – a maze of fluid-filled channels in the inner ear. Vestibular neuritis is inflammation of the vestibular nerve – the nerve in the inner ear that sends messages related to motion and position t ...
, by a bad
common cold
The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after exposu ...
affecting the head or a number of other medical conditions including but not limited to
vertigo
Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...
. It can also be temporarily disturbed by quick or prolonged
acceleration
In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...
, for example, riding on a
merry-go-round
A carousel or carrousel (mainly North American English), merry-go-round (List of sovereign states, international), roundabout (British English), or hurdy-gurdy (an old term in Australian English, in South Australia, SA) is a type of amusement ...
. Blows can also affect equilibrioreception, especially those to the side of the head or directly to the ear.
Most
astronaut
An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...
s find that their sense of balance is impaired when in orbit because they are in a constant state of
weightlessness
Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G.
Weight is a measurement of the force on an object at rest in a relatively strong gravitational fi ...
. This causes a form of
motion sickness
Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include nausea, vomiting, cold sweat, headache, dizziness, tiredness, loss of appetite, and increased salivation. Complications may rarely include d ...
called
space adaptation syndrome.
System overview
This overview also explains acceleration as its processes are interconnected with balance.
Mechanical
There are five
sensory organs
A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...
innervated
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
by the
vestibular nerve
The vestibular nerve is one of the two branches of the vestibulocochlear nerve (the cochlear nerve being the other). In humans the vestibular nerve transmits sensory information transmitted by vestibular hair cells located in the two otolith orga ...
; three
semicircular canals
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
Structure
The ...
(
Horizontal SCC,
Superior SCC,
Posterior SCC) and two
otolith
An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
organs (
saccule
The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves verticall ...
and
utricle). Each semicircular canal (SSC) is a thin tube that doubles in thickness briefly at a point called
osseous ampullae
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
Structure
The ...
. At their center-base, each contains an
ampullary cupula
The ampullary cupula, or cupula, is a structure in the vestibular system, providing the sense of spatial orientation.
The cupula is located within the ampullae of each of the three semicircular canals. Part of the crista ampullaris, the cupula ha ...
. The cupula is a gelatin bulb connected to the
stereocilia
Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cel ...
of hair cells, affected by the relative movement of the
endolymph
Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. I ...
it is bathed in.
Since the cupula is part of the
bony labyrinth
The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the su ...
, it rotates along with actual head movement, and by itself without the endolymph, it cannot be stimulated and therefore, could not detect movement. Endolymph follows the rotation of the canal; however, due to
inertia
Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
its movement initially lags behind that of the bony labyrinth. The delayed movement of the endolymph bends and activates the cupula. When the cupula bends, the connected stereocilia bend along with it, activating chemical reactions in the hair cells surrounding
crista ampullaris
The crista ampullaris is the sensory organ of rotation. They are found in the osseous ampullae, ampullae of each of the semicircular canals of the inner ear, meaning that there are three pairs in total. The function of the crista ampullaris is to ...
and eventually create
action potentials
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, c ...
carried by the vestibular nerve signaling to the body that it has moved in space.
After any extended rotation, the endolymph catches up to the canal and the cupula returns to its upright position and resets. When extended rotation ceases, however, endolymph continues, (due to inertia) which bends and activates the cupula once again to signal a change in movement.
Pilots doing long banked turns begin to feel upright (no longer turning) as endolymph matches canal rotation; once the pilot exits the turn the cupula is once again stimulated, causing the feeling of turning the other way, rather than flying straight and level.
The horizontal SCC handles head rotations about a vertical axis (e.g. looking side to side), the superior SCC handles head movement about a lateral axis (e.g. head to shoulder), and the posterior SCC handles head rotation about a
rostral-caudal axis (e.g. nodding). SCC sends adaptive signals, unlike the two otolith organs, the saccule and utricle, whose signals do not adapt over time.
A shift in the
otolithic membrane that stimulates the cilia is considered the state of the body until the cilia are once again stimulated. For example, lying down stimulates cilia and standing up stimulates cilia, however, for the time spent lying the signal that you are lying remains active, even though the membrane resets.
Otolithic organs
An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle (ear), utricle of the inner ear, specifically in the vestibular system of verteb ...
have a thick, heavy gelatin membrane that, due to inertia (like endolymph), lags behind and continues ahead past the
macula
The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...
it overlays, bending and activating the contained cilia.
Utricle responds to linear accelerations and head-tilts in the horizontal plane (head to shoulder), whereas
saccule
The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves verticall ...
responds to linear accelerations and head-tilts in the vertical plane (up and down). Otolithic organs update the brain on the head-location when not moving; SCC update during movement.
Kinocilium
A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear.
Anatomy in humans
Kinocilia are found on the apical surface of hair cells and are involved in both the morphogenesis ...
are the longest stereocilia and are positioned (one per 40-70 regular cilia) at the end of the bundle. If stereocilia go towards kinocilium,
depolarization
In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is esse ...
occurs, causing more
neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Neuro ...
s, and more vestibular nerve firings, as compared to when stereocilia tilt away from kinocilium (
hyperpolarization, less neurotransmitter, less firing).
Neural
First order
vestibular nuclei
The vestibular nuclei (VN) are the cranial nuclei for the vestibular nerve located in the brainstem.
In Terminologia Anatomica they are grouped in both the pons and the medulla in the brainstem.
Structure Path
The fibers of the vestibular nerve ...
(VN) project to
lateral vestibular nucleus
The lateral vestibular nucleus (Deiters's nucleus) is the continuation upward and lateralward of the principal nucleus, and in it terminate many of the ascending branches of the vestibular nerve.
Structure
It consists of very large multipolar cel ...
(IVN),
medial vestibular nucleus
The medial vestibular nucleus (Schwalbe nucleus) is one of the vestibular nuclei. It is located in the medulla oblongata.
Lateral vestibulo-spinal tract (lateral vestibular nucleus “Deiters”)- via ventrolateral medulla and spinal cord to ventr ...
(MVN), and
superior vestibular nucleus
The superior vestibular nucleus ( Bechterew's nucleus) is the dorso-lateral part of the vestibular nucleus and receives collaterals and terminals from the ascending branches of the vestibular nerve
The vestibular nerve is one of the two branches ...
(SVN).
The
inferior cerebellar peduncle
The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle, a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerv ...
is the largest center through which balance information passes. It is the area of integration between
proprioceptive
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
, and vestibular inputs, to aid in unconscious maintenance of balance and posture.
The
inferior olivary nucleus
The inferior olivary nucleus (ION), is a structure found in the medulla oblongata underneath the superior olivary nucleus.Gado, Thomas A. Woolsey; Joseph Hanaway; Mokhtar H. (2003). The brain atlas a visual guide to the human central nervous syst ...
aids in complex
motor tasks by encoding coordinating timing sensory information; this is decoded and acted upon in the
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
.
The
cerebellar vermis
The cerebellar vermis (from Latin ''vermis,'' "worm") is located in the medial, cortico-nuclear zone of the cerebellum, which is in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior ...
has three main parts. The
vestibulocerebellum
The anatomy of the cerebellum can be viewed at three levels. At the level of gross anatomy, the cerebellum consists of a tightly folded and crumpled layer of cortex, with white matter underneath, several deep nuclei embedded in the white matte ...
regulates eye movements by the integration of visual info provided by the
superior colliculus
In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form ''tectal'' is commonly ...
and balance information. The
spinocerebellum
The anatomy of the cerebellum can be viewed at three levels. At the level of gross anatomy, the cerebellum consists of a tightly folded and crumpled layer of cortex, with white matter underneath, several deep nuclei embedded in the white matte ...
integrates visual, auditory, proprioceptive, and balance information to act out body and limb movements. It receives input from the
trigeminal nerve
In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...
, dorsal column (of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...
),
midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', " ...
,
thalamus
The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...
,
reticular formation
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation ...
and vestibular nuclei (
medulla
Medulla or Medullary may refer to:
Science
* Medulla oblongata, a part of the brain stem
* Renal medulla, a part of the kidney
* Adrenal medulla, a part of the adrenal gland
* Medulla of ovary, a stroma in the center of the ovary
* Medulla of t ...
) outputs. Lastly, the
cerebrocerebellum plans, times, and initiates movement after evaluating sensory input from, primarily, motor cortex areas, via
pons
The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.
The pons is also called the pons Varolii ("bridge of Va ...
and cerebellar
dentate nucleus
The dentate nucleus is a cluster of neurons, or nerve cells, in the central nervous system that has a dentate – tooth-like or serrated – edge. It is located within the deep white matter of each cerebellar hemisphere, and it is the largest sin ...
. It outputs to the thalamus,
motor cortex
The motor cortex is the region of the cerebral cortex believed to be involved in the planning, control, and execution of voluntary movements.
The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately a ...
areas, and
red nucleus
The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. The red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin. ...
.
The
flocculonodular lobe
The flocculonodular lobe (vestibulocerebellum) is a lobe of the cerebellum consisting of the nodule and the flocculus. The two flocculi are connected to the midline structure called the nodulus by thin pedicles. It is placed on the anteroinferio ...
is a cerebellar lobe that helps maintain body equilibrium by modifying
muscle tone
In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial muscle contraction, contraction of the muscles, or the muscle's resistance to passive stretch during resting state.O’Sull ...
(the continuous and passive muscle contractions).
MVN and IVN are in the medulla, LVN and SVN are smaller and in pons. SVN, MVN, and IVN ascend within the
medial longitudinal fasciculus
The medial longitudinal fasciculus (MLF) is an area of crossed over tracts, on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem. They are made up of both ascending and descending fibers that ari ...
. LVN descend the spinal cord within the
lateral vestibulospinal tract
The lateral vestibulospinal tract is one of the descending spinal tracts of the ventromedial funiculus.
The lateral part of the vestibulospinal tract is the major portion and is composed of fibers originating in the lateral, superior, and inferior ...
and ends at the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
. MVN also descend the spinal cord, within the
medial vestibulospinal tract
The medial vestibulospinal tract is one of the descending spinal tracts of the ventromedial funiculus of the spinal cord. It is found only in the cervical spine and above.
The medial part of the vestibulospinal tract is the smaller part, and is pr ...
, ending at
lumbar 1.
The
thalamic reticular nucleus
The thalamic reticular nucleus is part of the ventral thalamus that forms a capsule around the thalamus laterally. However, recent evidence from mice and fish question this statement and define it as a dorsal thalamic structure. It is separated fro ...
distributes information to various other thalamic nuclei, regulating the flow of information. It is speculatively able to stop signals, ending transmission of unimportant info. The thalamus relays info between pons (cerebellum link), motor cortices, and
insula.
The insula is also heavily connected to motor cortices; the insula is likely where balance is likely brought into perception.
The
oculomotor nuclear complex refers to fibers going to
tegmentum
The tegmentum (from Latin for "covering") is a general area within the brainstem. The tegmentum is the ventral part of the midbrain and the tectum is the dorsal part of the midbrain. It is located between the ventricular system and distinctive b ...
(eye movement), red nucleus (
gait
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency. Di ...
(natural limb movement)),
substantia nigra
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra app ...
(reward), and
cerebral peduncle
The cerebral peduncles are the two stalks that attach the cerebrum to the brainstem. They are structures at the front of the midbrain which arise from the ventral pons and contain the large ascending (sensory) and descending (motor) nerve tra ...
(motor relay). Nucleus of Cajal are one of the named oculomotor nuclei, they are involved in eye movements and reflex gaze coordination.
The
abducens nerve
The abducens nerve or abducent nerve, also known as the sixth cranial nerve, cranial nerve VI, or simply CN VI, is a cranial nerve in humans and various other animals that controls the movement of the lateral rectus muscle, one of the extraocula ...
solely innervates the
lateral rectus muscle
Lateral is a geometric term of location which may refer to:
Healthcare
*Lateral (anatomy), an anatomical direction
*Lateral cricoarytenoid muscle
*Lateral release (surgery), a surgical procedure on the side of a kneecap
Phonetics
*Lateral cons ...
of the eye, moving the eye with the
trochlear nerve
The trochlear nerve (), ( lit. ''pulley-like'' nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates just one muscle: the superior oblique muscle of the eye, which operates through the pul ...
. The trochlear solely innervates the
superior oblique muscle
The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye. It is the only extraocular musc ...
of the eye. Together, trochlear and abducens contract and relax to simultaneously direct the pupil towards an angle and depress the globe on the opposite side of the eye (e.g. looking down directs the pupil down and depresses (towards the brain) the top of the globe). The pupil is not only directed, but often rotated, by these muscles. (See
visual system
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
)
The thalamus and superior colliculus are connected via the
lateral geniculate nucleus
In neuroanatomy, the lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projec ...
. The superior colliculus (SC) is the
topographical map
In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but historic ...
for balance and quick orienting movements with primarily visual inputs. SC integrates multiple senses.
Other animals
Some animals have better equilibrioception than humans; for example, a
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
uses its
inner ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
and
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
to walk on a thin
fence
A fence is a structure that encloses an area, typically outdoors, and is usually constructed from posts that are connected by boards, wire, rails or netting. A fence differs from a wall in not having a solid foundation along its whole length.
...
.
Equilibrioception in many marine animals is done with an entirely different organ, the
statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in ''Xenoturbella''. The statocyst cons ...
, which detects the position of tiny
calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an adje ...
stones to determine which way is "up".
In plants
Plants could be said to exhibit a form of equilibrioception, in that when rotated from their normal attitude the stems grow in the direction that is upward (away from gravity) while their roots grow downward (in the direction of gravity). This phenomenon is known as
gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general featu ...
and it has been shown that, for example,
poplar stems can detect reorientation and inclination.
*
Balance disorder
A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance ...
*
Broken escalator phenomenon
The broken escalator phenomenon, also known as the escalator effect and the Walker effect, is the sensation of losing balance, confusion or dizziness reported by some people when stepping onto an escalator which is not working. It is said that ther ...
*
Dizziness
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Dizziness is a common medical c ...
*
Ernst Mach
Ernst Waldfried Josef Wenzel Mach ( , ; 18 February 1838 – 19 February 1916) was a Moravian-born Austrian physicist and philosopher, who contributed to the physics of shock waves. The ratio of one's speed to that of sound is named the Mach ...
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Ideomotor phenomenon
The ideomotor phenomenon is a psychological phenomenon wherein a subject makes motions unconsciously. Also called ideomotor response (or ideomotor reflex) and abbreviated to IMR, it is a concept in hypnosis and psychological research. It is deri ...
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Illusions of self-motion
Illusions of self-motion (or "vection") occur when one perceives bodily motion despite no movement taking place. One can experience illusory movements of the whole body or of individual body parts, such as arms or legs.
Vestibular illusions
The v ...
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Motion sickness
Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include nausea, vomiting, cold sweat, headache, dizziness, tiredness, loss of appetite, and increased salivation. Complications may rarely include d ...
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Proprioception
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
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Seasickness
Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include nausea, vomiting, cold sweat, headache, dizziness, tiredness, loss of appetite, and increased salivation. Complications may rarely include d ...
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Spatial disorientation
Spatial disorientation results in a person being unable to determine their position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular ...
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Vertigo
Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...
Training devices
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Balance ball
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Balance board
A balance board is a device used as a circus skill, for recreation, balance training, athletic training, brain development, therapy, musical training and other kinds of personal development.
It is a lever similar to a see-saw that the use ...
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Balance bicycle
A balance bicycle, run bike or no pedal bike or dandy horse is a training bicycle that helps children learn balance and steering. It has no foot pedals, no drivetrain, no chain, no gears, no gear shifters, no derailleurs, and no freewheel.
Desig ...
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BOSU
A BOSU Balance Trainer (or BOSU ball) is a fitness training device, invented in 1999 by David Weck. It consists of an inflated rubber Sphere, hemisphere attached to a rigid platform. The device is often used for Balance (ability), balance trainin ...
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Slackline
Slacklining refers to the act of walking, running or balance (ability), balancing along a suspended length of flat webbing that is tension (physics), tensioned between two anchor (climbing), anchors. Slacklining is similar to Slackwire#Slack rope ...
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Tight rope
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Unicycle
A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a bicycle frame, frame with a bicycle saddle, saddle, and has a human-powered vehicle, pedal-driven direct-drive mechanism, direct-drive. A two spee ...
References
External links
{{Authority control
Vestibular system
Sensory systems
Motor control