12. The vestibular system and our sense of
equilibrium
Mvt = movement; envt = environment; = = is/are; btwn = between; w/ = with; e = eye(s); v =
vestibular/vestibulo; s = system ; scc = semicircular canal(s)
Vestibular organs = set of 5 sense organs (3 semicircular canals and two otolith organs) located in each
inner ear that sense head motion and head orientation with respect to gravity.
Equilibrium = our vestibular sense comprised of spatial orientation perception – encompassing our
perception of linear motion, angular motion, and tilt – combined with reflexive vestibular responses like
posture, vestibulo-autonomic reflexes and vestibulo-ocular reflexes.
V organs = set of specialized sense organs located in the inner ear next to the cochlea. V organs sense
motion of the head, the orientation of gravity and make a predominant contribution to our sense of tilt
and our sense of self-motion. Tilt + self-motion = spatial orientation.
Spatial orientation = sense consisting of three interacting modalities: perception of linear motion, angular
motion and tilt.
Vestibular system = vestibular organs and neural pathways directly associated with these sense organs.
It contributes to clear vision when we move & help us maintain balance when we stand. It is a sixth sense.
Vertigo = sensation of rotation or spinning. Often used more generally to mean any form of dizziness.
Vestibulo-ocular reflex (VOR) = short-latency reflex that helps stabilize vision by counterrotating the eyes
when the vestibular system senses head mvt.
We can compensate for head mvt more readily than hand mvt because of the VOR.
It is not that we are unable to perceive vestibular stimulation, but rather that vestibular stimulation is
almost always relegated to the attentional background.
Vestibular contributions to equilibrium
Vs → critical contributions to balance. Our sense of equilibrium is active, not passive.
Balance = neural process of postural control by which weight is evenly distributed, enabling us to remain
upright and stable.
Kinaesthetic = perception of the position & mvt of our limbs in space.
Afferent signals = information flowing inward to the central nervous system from sensors in the
periphery. Passive sensing would rely exclusively on such sensory inflow, providing a traditional view of
sensation.
The vestibular system contributes to our sense of equilibrium, which is composed of many fundamental
reflexes and perceptual modalities. However, the vs does not exclusively provide the sensory foundation
for any perceptual modality. Nonetheless, the breadth of the vs’s contributions is amazing. When
combined, these various perceptual and reflexive contributions are referred to as our sense of equilibrium
because these various contributions involve a balance of influences and/or a balance of forces – matching
definitions of equilibrium you might find in a dictionary.
Modalities and qualities of spatial orientation
Angular motion = rotational motion like the rotation of a spinning top or swinging saloon doors that rotate
back and forth.
, Linear motion = translational motion like the predominant mvt of a train car or bobblehead doll.
Tilt = attain a sloped position like that of the Leaning Tower of Pisa.
Together, these three sensory modalities form our perception of spatial orientation.
Vision and hearing are different modalities, but colour and brightness are different qualities. Thus, these
three are different modalities. Why? → as with seeing and hearing, perceiving angular motion, linear
motion and tilt requires that three different stimuli (angular acceleration, linear acceleration and gravity)
be transduced.
Transduce (energy) = to convert from one form of energy to another (ex: from light to neural electrical
energy, from mechanical energy to neural electrical energy).
Sensing angular motion, linear motion and tilt
Semicircular canal = any of the 3 toroidal tubes in the vs that sense angular motion.
Angular acceleration = rate of change of angular velocity. Mathematically, angular acceleration, angular
velocity and angular displacement represent angular motion.
The semicircular canals sense angular acceleration. On the other hand, the otolith organs transduce both
linear acceleration and gravity.
Otolith organ = either of 2 mechanical structures (utricle and saccule) in the vestibular system that sense
both linear acceleration and gravity.
Linear acceleration = rate of change of linear velocity. Linear acceleration&velocity&displacement all
mathematically represent linear motion.
Gravity = force that attracts a body toward the centre of the Earth.
There are three interacting sensory modalities linked to the three different sources of stimulation energy:
the sense of angular motion (the perceptual modality that senses rotation), the sense of linear motion
(the perceptual modality that senses translation) and the sense of tilt (the perceptual modality that senses
head inclination with respect to gravity).
Basic qualities of spatial orientation: amplitude and direction
Each of our three spatial orientation modalities include two qualities: amplitude and direction.
Amplitude = the size of a head mvt (ex: angular velocity, linear acceleration, tilt).
equilibrium
Mvt = movement; envt = environment; = = is/are; btwn = between; w/ = with; e = eye(s); v =
vestibular/vestibulo; s = system ; scc = semicircular canal(s)
Vestibular organs = set of 5 sense organs (3 semicircular canals and two otolith organs) located in each
inner ear that sense head motion and head orientation with respect to gravity.
Equilibrium = our vestibular sense comprised of spatial orientation perception – encompassing our
perception of linear motion, angular motion, and tilt – combined with reflexive vestibular responses like
posture, vestibulo-autonomic reflexes and vestibulo-ocular reflexes.
V organs = set of specialized sense organs located in the inner ear next to the cochlea. V organs sense
motion of the head, the orientation of gravity and make a predominant contribution to our sense of tilt
and our sense of self-motion. Tilt + self-motion = spatial orientation.
Spatial orientation = sense consisting of three interacting modalities: perception of linear motion, angular
motion and tilt.
Vestibular system = vestibular organs and neural pathways directly associated with these sense organs.
It contributes to clear vision when we move & help us maintain balance when we stand. It is a sixth sense.
Vertigo = sensation of rotation or spinning. Often used more generally to mean any form of dizziness.
Vestibulo-ocular reflex (VOR) = short-latency reflex that helps stabilize vision by counterrotating the eyes
when the vestibular system senses head mvt.
We can compensate for head mvt more readily than hand mvt because of the VOR.
It is not that we are unable to perceive vestibular stimulation, but rather that vestibular stimulation is
almost always relegated to the attentional background.
Vestibular contributions to equilibrium
Vs → critical contributions to balance. Our sense of equilibrium is active, not passive.
Balance = neural process of postural control by which weight is evenly distributed, enabling us to remain
upright and stable.
Kinaesthetic = perception of the position & mvt of our limbs in space.
Afferent signals = information flowing inward to the central nervous system from sensors in the
periphery. Passive sensing would rely exclusively on such sensory inflow, providing a traditional view of
sensation.
The vestibular system contributes to our sense of equilibrium, which is composed of many fundamental
reflexes and perceptual modalities. However, the vs does not exclusively provide the sensory foundation
for any perceptual modality. Nonetheless, the breadth of the vs’s contributions is amazing. When
combined, these various perceptual and reflexive contributions are referred to as our sense of equilibrium
because these various contributions involve a balance of influences and/or a balance of forces – matching
definitions of equilibrium you might find in a dictionary.
Modalities and qualities of spatial orientation
Angular motion = rotational motion like the rotation of a spinning top or swinging saloon doors that rotate
back and forth.
, Linear motion = translational motion like the predominant mvt of a train car or bobblehead doll.
Tilt = attain a sloped position like that of the Leaning Tower of Pisa.
Together, these three sensory modalities form our perception of spatial orientation.
Vision and hearing are different modalities, but colour and brightness are different qualities. Thus, these
three are different modalities. Why? → as with seeing and hearing, perceiving angular motion, linear
motion and tilt requires that three different stimuli (angular acceleration, linear acceleration and gravity)
be transduced.
Transduce (energy) = to convert from one form of energy to another (ex: from light to neural electrical
energy, from mechanical energy to neural electrical energy).
Sensing angular motion, linear motion and tilt
Semicircular canal = any of the 3 toroidal tubes in the vs that sense angular motion.
Angular acceleration = rate of change of angular velocity. Mathematically, angular acceleration, angular
velocity and angular displacement represent angular motion.
The semicircular canals sense angular acceleration. On the other hand, the otolith organs transduce both
linear acceleration and gravity.
Otolith organ = either of 2 mechanical structures (utricle and saccule) in the vestibular system that sense
both linear acceleration and gravity.
Linear acceleration = rate of change of linear velocity. Linear acceleration&velocity&displacement all
mathematically represent linear motion.
Gravity = force that attracts a body toward the centre of the Earth.
There are three interacting sensory modalities linked to the three different sources of stimulation energy:
the sense of angular motion (the perceptual modality that senses rotation), the sense of linear motion
(the perceptual modality that senses translation) and the sense of tilt (the perceptual modality that senses
head inclination with respect to gravity).
Basic qualities of spatial orientation: amplitude and direction
Each of our three spatial orientation modalities include two qualities: amplitude and direction.
Amplitude = the size of a head mvt (ex: angular velocity, linear acceleration, tilt).
