Spatial Orientation and the Vestibular System

Question 1

sense of linear motion

Answer 1

The spatial orientation modality that senses translation.

Question 2

dizziness

Answer 2

A commonly used lay term that nonspecifically indicates any form of perceived spatial disorientation, with or without instability.

Question 2

transduce

Answer 2

To convert from one form of energy to another (e.g., from light to neural electrical energy, or from mechanical movement to neural electrical energy).

Question 3

amplitude

Answer 3

The size (increase or decrease) of a head movement (e.g., angular velocity, linear acceleration, tilt).

Question 3

balance

Answer 3

The neural processes of postural control by which weight is evenly distributed, enabling us to remain upright and stable.

Question 3

tilt

Answer 3

Attaining a sloping position like that of the leaning tower of Pisa.

Question 3

vertigo

Answer 3

A sensation of rotation or spinning. The term is sometimes used erroneously to mean any form of dizziness.

Question 4

mechanoreceptor

Answer 4

A sensory receptor that responds to mechanical stimulation (pressure, vibration, or movement).

Question 5

spatial disorientation

Answer 5

Any impairment of spatial orientation. More specifically, any impairment of our sense of linear motion, angular motion, or tilt.

Question 6

utricle

Answer 6

One of the two otolith organs. A saclike structure that contains the utricular macula. Also called utriculus.

Question 8

autonomic nervous system

Answer 8

The part of the nervous system that innervates glands, heart, digestive system, and so on, and that is responsible for regulating many involuntary actions.

Question 9

hair cell

Answer 9

Any cell that has stereocilia for transducing mechanical movement in the inner ear into neural activity sent to the brain; some hair cells also receive inputs from the brain.

Question 9

receptor potential

Answer 9

A change in voltage across the membrane of a sensory receptor cell (in the vestibular system, a hair cell) in response to stimulation.

Question 10

sinusoidal

Answer 10

Referring to any oscillation, such as a sound wave or rotational motion, whose waveform is that of a sine curve. The period of a sinusoidal oscillation is the time that it takes for one full back-and-forth cycle of the motion to occur. The frequency of a sinusoidal oscillation is defined as the numeral 1 divided by the period.

Question 12

angular motion

Answer 12

Rotational motion like the rotation of a spinning top or swinging saloon doors that rotate back and forth.

Question 13

spatial orientation

Answer 13

A sense consisting of three interacting sensory modalities: the senses of linear motion, angular motion, and tilt.

Question 14

direction

Answer 14

The line along which one faces or moves, with reference to the point or region toward which one is facing or moving.

Question 15

vestibular organs

Answer 15

The set of five organs—three semicircular canals and two otolith organs—located in each inner ear that sense head motion and head orientation with respect to gravity. These organs are also sometimes called the vestibular system or the vestibular labyrinth, but the name vestibular system is often used more generally to refer to the vestibular organs and their neural pathways.

Question 17

angular acceleration

Answer 17

The rate of change of angular velocity. Mathematically, the integral of angular acceleration is angular velocity, and the integral of angular velocity is angular displacement. Angular acceleration, angular velocity, and angular displacement all mathematically represent angular motion.

Question 17

otoconia

Answer 17

Tiny calcium carbonate stones in the ear that provide inertial mass for the otolith organs, enabling them to sense gravity and linear acceleration.

Question 17

sense of tilt

Answer 17

The spatial orientation modality that senses head inclination with respect to gravity.

Question 19

macula

Answer 19

Any of the specialized detectors of linear acceleration and gravity found in each otolith organ.

Question 20

sense of angular motion

Answer 20

The spatial orientation modality that senses rotation.

Question 22

ampulla

Answer 22

An expansion of each semicircular canal duct that includes that canal’s cupula, crista, and hair cells, where transduction occurs.

Question 22

balance system

Answer 22

The sensory systems, neural processes, and muscles that contribute to postural control. Specific components include the vestibular labyrinth, proprioceptors, vestibulo-spinal pathways, and postural control muscles. Because of its crucial contributions to balance, some even informally refer to the vestibular system as the balance system and the vestibular organs as the balance organs. But the balance system is much more than just the vestibular system, and the vestibular system contributes to much more than just balance.

Question 23

Fourier analysis

Answer 23

A mathematical procedure by which any signal—in this case motion trajectories as a function of time—can be separated into component sine waves at different frequencies. Combining these sine waves will reproduce the original motion trajectory.

Question 24

vestibulo-ocular reflex (VOR)

Answer 24

A short-latency reflex that helps stabilize vision by counterrotating the eyes when the vestibular system senses head movement.

Question 25

otolith organ

Answer 25

Either of two mechanical structures (utricle and saccule) in the vestibular system that sense both linear acceleration and gravity.

Question 26

mathematical integration

Answer 26

Computing an integral—one of the two main operations in calculus (the other, the inverse operation, is differentiation). Velocity is the integral of acceleration. Change of position is the integral of velocity.

Question 28

semicircular canal

Answer 28

Any of three toroidal tubes in the vestibular system that sense angular motion.

Question 29

gravity

Answer 29

A force that attracts a body toward the center of the Earth.

Question 30

crista

Answer 30

Any of the specialized detectors of angular motion located in each semicircular canal in a swelling called the ampulla.

Question 31

vection

Answer 31

An illusory sense of self-motion caused by moving visual cues when you are not, in fact, actually moving.

Question 32

saccule

Answer 32

One of the two otolith organs. A saclike structure that contains the saccular macula. Also called sacculus.

Question 34

linear acceleration

Answer 34

The rate of change of linear velocity. Mathematically, the integral of linear acceleration is linear velocity, and the integral of linear velocity is linear displacement, which is also referred to as “translation.” Linear acceleration, linear velocity, and linear displacement all mathematically represent linear motion.

Question 35

acceleration

Answer 35

A change in velocity. Mathematically, acceleration is the derivative of velocity. In words, linear acceleration indicates a change in linear velocity; angular acceleration indicates a change in angular velocity.

Question 36

sensory integration

Answer 36

The process of combining different sensory signals. Typically, combining several signals yields more accurate and/or more precise information than can be obtained from individual sensory signals. This is not the mathematical process of integration learned in calculus (e.g., the integral of acceleration is velocity).

Question 37

cilium

Answer 37

Any of the hairlike structures that move as part of vestibular transduction. The vestibular system includes two types of cilia: kinocilia and stereocilia.

Question 39

velocity

Answer 39

The speed and direction in which something moves. Mathematically, velocity is the integral of acceleration. In words, linear velocity is the ratio of the distance moved divided by the time it takes to traverse that distance; angular velocity is the ratio of the angle rotated divided by the time it takes to traverse that angle.

Question 40

oscillatory

Answer 40

Referring to back-and-forth movement that has a constant rhythm.

Question 41

imbalance

Answer 41

Lack of balance; unsteadiness; nearly falling over.

Question 42

linear motion

Answer 42

Translational motion like the predominant movement of a train car or bobblehead doll.