Lecture 7: Auditory and Balance

Question 1

Describe the main functions of the ear.

Answer 1

The ear is responsible for hearing and equilibrium (balance).

Question 2

Explain how fluids in the ear contribute to hearing and balance.

Answer 2

Fluids must be moved to stimulate the mechanoreceptors located in the internal ear, which are essential for both hearing and equilibrium.

Question 3

Define the three major areas of the ear and their functions.

Answer 3

The ear has three major areas: the external ear (hearing only), the middle ear (hearing only), and the internal ear (hearing and equilibrium).

Question 4

How does the auricle (pinna) function in the ear?

Answer 4

The auricle (pinna) is a shell-shaped structure that funnels sound waves into the auditory canal.

Question 5

What is the role of the tympanic membrane (eardrum)?

Answer 5

The tympanic membrane serves as the boundary between the external and middle ears, vibrating in response to sound and transferring sound energy to the bones of the middle ear.

Question 6

Describe the structure and function of the middle ear.

Answer 6

The middle ear is a small, air-filled cavity in the temporal bone that contains the tympanic membrane and auditory ossicles, facilitating the transmission of sound.

Question 7

Explain the function of the pharyngotympanic (auditory) tube.

Answer 7

The pharyngotympanic tube connects the middle ear to the nasopharynx and helps equalize pressure in the middle ear cavity with external air pressure.

Question 8

What are the auditory ossicles and their roles in hearing?

Answer 8

The auditory ossicles are three small bones in the tympanic cavity: malleus (hammer), incus (anvil), and stapes (stirrup), which transmit vibratory motion from the eardrum to the oval window.

Question 9

How do the tensor tympani and stapedius muscles protect hearing?

Answer 9

These muscles contract reflexively in response to loud sounds to prevent damage to the hearing receptors.

Question 10

Identify the components of the external ear.

Answer 10

The external ear consists of the auricle (pinna), helix, lobule, and external acoustic meatus (auditory canal).

Question 11

Describe the epitympanic recess and its location.

Answer 11

The epitympanic recess is the superior portion of the middle ear, located above the tympanic cavity.

Question 11

What happens if the pressures on both sides of the tympanic membrane are not equal?

Answer 11

If pressures are not equal, the tympanic membrane cannot vibrate efficiently, leading to distorted sounds.

Question 12

What is the function of the mastoid antrum?

Answer 12

The mastoid antrum is a canal that allows communication with the mastoid air cells in the mastoid process.

Question 13

How does the structure of the external acoustic meatus contribute to its function?

Answer 13

The external acoustic meatus is a short, curved tube lined with skin, hairs, and glands that transmits sound waves to the eardrum.

Question 14

Explain the significance of the oval and round windows in the middle ear.

Answer 14

The oval and round windows are membranous structures in the bony wall of the middle ear that play a role in sound transmission and pressure regulation.

Question 15

What is the role of the trigeminal nerve in relation to the ear?

Answer 15

The trigeminal nerve (V) provides motor input to the tensor tympani muscle, which helps protect hearing.

Question 16

Describe the bony labyrinth of the inner ear.

Answer 16

The bony labyrinth is a system of tortuous channels and cavities that worm through the bone, divided into three regions: vestibule, semicircular canals, and cochlea. It is filled with perilymph fluid, which is similar to cerebrospinal fluid.

Question 17

Explain the function of the membranous labyrinth.

Answer 17

The membranous labyrinth consists of a series of membranous sacs and ducts contained within the bony labyrinth, filled with potassium-rich endolymph. It plays a crucial role in balance and hearing.

Question 18

Define the role of the saccule and utricle in the inner ear.

Answer 18

The saccule and utricle are membranous sacs within the bony labyrinth that house equilibrium receptor regions called maculae, which respond to gravity and changes in head position.

Question 19

How are the semicircular canals oriented in relation to each other?

Answer 19

The three semicircular canals are oriented in three planes of space: the anterior and posterior canals are at right angles to each other, while the lateral canal is horizontal.

Question 20

What is the function of the ampulla in the semicircular canals?

Answer 20

The ampulla is the enlarged area of the ducts of each semicircular canal that houses the equilibrium receptor region called the crista ampullaris, which responds to angular (rotational) movements of the head.

Question 21

Describe the structure and function of the cochlea.

Answer 21

The cochlea is a small spiral, conical, bony chamber that extends from the vestibule and coils around a bony pillar called the modiolus. It contains the cochlear duct, which houses the spiral organ (organ of Corti) and is responsible for hearing.

Question 22

Explain the significance of the scalae in the cochlea.

Answer 22

The cochlea is divided into three chambers: scala vestibuli, scala media (cochlear duct), and scala tympani. The scala vestibuli and scala tympani contain perilymph and are continuous with each other at the helicotrema, while the scala media contains endolymph.

Question 23

What is the role of the stria vascularis in the cochlear duct?

Answer 23

The stria vascularis is the external wall of the cochlear duct composed of mucosa that secretes endolymph, which is essential for the function of the hair cells in hearing.

Question 24

Describe the arrangement of hair cells in the spiral organ.

Answer 24

The spiral organ contains cochlear hair cells arranged in one row of inner hair cells and three rows of outer hair cells, sandwiched between the tectorial and basilar membranes.

Question 25

How does sound vibration affect the tympanic membrane?

Answer 25

Sound waves enter the external acoustic meatus and strike the tympanic membrane, causing it to vibrate. The intensity of the sound affects the degree of vibration.

Question 26

Explain the function of the auditory ossicles in hearing.

Answer 26

The auditory ossicles transfer the vibration of the eardrum to the oval window, facilitating the transmission of sound waves into the inner ear.

Question 27

What happens to sound waves in the scala vestibuli?

Answer 27

In the scala vestibuli, the stapes rocks back and forth on the oval window with each vibration, creating wave motions in the perilymph that travel through the cochlea.

Question 28

Describe the path of sound waves through the cochlea.

Answer 28

Sound waves in the hearing range travel through the cochlear duct, vibrating the basilar membrane at specific locations according to the frequency of the sound.

Question 29

What is resonance in the context of the basilar membrane?

Answer 29

Resonance refers to the movement of different areas of the basilar membrane in response to a particular frequency of sound, allowing for the mechanical processing of sound.

Question 30

How does the structure of the basilar membrane change along its length?

Answer 30

The basilar membrane has fibers near the oval window that are short and stiff, resonating with high-frequency waves, while fibers near the cochlear apex are longer and floppier, resonating with lower-frequency waves.

Question 31

Explain the process of excitation of inner hair cells in the cochlea.

Answer 31

Movement of the basilar membrane deflects the hairs of inner hair cells, with stereocilia projecting into the K+-rich endolymph and the longest hairs enmeshed in the gel-like tectorial membrane, transforming mechanical energy into electrical signals.

Question 32

Describe the role of cochlear hair cells in auditory processing.

Answer 32

Cochlear hair cells have stereocilia that bend at their base in response to mechanical deflection, which excites the hair cells and initiates neural signals for sound processing.

Question 33

Explain how tip links function in hair cells.

Answer 33

Tip links connect the longest hair cells to the shortest ones, and when they are pulled on, they open ion channels, allowing ions to flow and generate neural signals.

Question 34

Do outer hair cells have a role in sound perception?

Answer 34

Yes, outer hair cells can contract and stretch, which changes the stiffness of the basilar membrane, enhancing the responsiveness of inner hair cells and protecting them from loud noises.

Question 35

How does the ascending auditory pathway function?

Answer 35

The ascending auditory pathway transmits auditory information from cochlear receptors (inner hair cells) to the cerebral cortex, with some fibers crossing over to the opposite side of the brain.

Question 36

Define the perception of pitch in relation to hair cells.

Answer 36

The perception of pitch is determined by the position of hair cells along the basilar membrane, where different positions correspond to specific frequencies of sound.

Question 37

Explain how loudness is detected by the brain.

Answer 37

Loudness is detected by the brain as an increase in the frequency of action potentials generated when hair cells experience larger deflections.

Question 38

Describe how sound localization occurs.

Answer 38

Sound localization depends on the relative intensity and timing of sound waves reaching both ears; differences in timing help the brain determine the direction of the sound.

Question 39

What is the vestibular apparatus and its function?

Answer 39

The vestibular apparatus consists of equilibrium receptors in the semicircular canals and vestibule, which help maintain balance and spatial orientation.

Question 40

Explain the difference between static and dynamic equilibrium.

Answer 40

Static equilibrium is monitored by vestibular receptors that detect the position of the head, while dynamic equilibrium is monitored by semicircular canal receptors that respond to head movements.

Question 41

What are maculae and their role in equilibrium?

Answer 41

Maculae are sensory receptor organs located in the saccule and utricle walls that monitor static equilibrium and respond to linear acceleration forces.

Question 42

Describe the anatomy of a macula.

Answer 42

A macula consists of a flat epithelial patch containing hair cells and supporting cells, with stereocilia embedded in an otolith membrane that contains otoliths.

Question 43

How do stereocilia contribute to the function of hair cells?

Answer 43

Stereocilia on hair cells bend in response to movement, which triggers the opening of ion channels and initiates the neural signaling process.

Question 44

What is the significance of kinocilium in hair cells?

Answer 44

Kinocilium is a special true stereocilium located next to the tallest stereocilia in hair cells, playing a crucial role in the detection of head position and movement.

Question 45

Describe the role of otoliths in the vestibular system.

Answer 45

Otoliths increase the weight and inertia of the membrane, helping to detect changes in head position.

Question 46

Explain the orientation of utricle maculae and their function.

Answer 46

Utricle maculae are horizontal with vertical hairs and respond to changes along a horizontal plane, such as tilting the head.

Question 47

How do forward and backward movements affect the utricle?

Answer 47

Forward and backward movements stimulate the utricle, allowing it to detect changes in head position.

Question 48

Define the orientation and function of saccule maculae.

Answer 48

Saccule maculae are vertical with horizontal hairs and respond to changes along a vertical plane, such as up and down movements.

Question 49

What type of movements stimulate the saccule?

Answer 49

Up and down movements, such as the acceleration of an elevator, stimulate the saccule.

Question 50

Explain the role of hair cells in the vestibular system.

Answer 50

Hair cells synapse with fibers of the vestibular nerve, continuously releasing neurotransmitters that change in response to acceleration or deceleration.

Question 51

Describe how changes in acceleration affect neurotransmitter release from hair cells.

Answer 51

Acceleration or deceleration causes a change in the amount of neurotransmitter released, which alters the action potential frequency sent to the brain.

Question 52

How does the density of the otolith membrane affect hair cell function?

Answer 52

The density of the otolith membrane causes it to lag behind the movement of hair cells, leading to bending of the hair cells when the head changes position.

Question 53

What happens when hair cells bend towards kinocilia?

Answer 53

Bending of hairs towards kinocilia depolarizes hair cells, increasing neurotransmitter release and the rate of impulses traveling to the brain.

Question 54

What is the effect of bending hair cells away from kinocilia?

Answer 54

Bending hairs away from kinocilia hyperpolarizes the receptors, reducing neurotransmitter release and decreasing the rate of impulse generation.

Question 55

Explain the function of the crista ampullaris in the vestibular system.

Answer 55

The crista ampullaris is a receptor for rotational acceleration, located in the ampulla of each semicircular canal, and responds to angular movements of the head.

Question 56

Describe how cristae detect rotational movements of the head.

Answer 56

Cristae are excited by acceleration and deceleration of the head, with inertia causing the endolymph to move in the opposite direction of the body's rotation, bending hair cells.

Question 57

What is the role of the ampullary cupula in the semicircular canals?

Answer 57

The ampullary cupula is a gel-like mass that hair cells extend into, playing a crucial role in detecting changes in head rotation.

Question 58

How do impulses from vestibular receptors reach the brain?

Answer 58

Impulses from activated vestibular receptors travel to vestibular nuclei in the brain stem or to the cerebellum.

Question 59

What are the three modes of input for balance and orientation?

Answer 59

The three modes of input for balance and orientation are vestibular receptors, visual receptors, and somatic receptors.

Question 60

Explain the effectiveness of cochlear implants for sensorineural deafness.

Answer 60

Cochlear implants convert sound energy into electrical signals and are effective for congenital or age/noise-related cochlear damage, allowing deaf children to learn to speak.

Question 61

How does the brain respond to changes in head position?

Answer 61

The brain is informed of changing head positions through the frequency of impulses generated by hair cells in response to head movements.

Question 62

Describe the insertion process of cochlear implants.

Answer 62

Cochlear implants are inserted into a drilled recess in the temporal bone to restore hearing.

Question 63

What is the significance of complementary semicircular ducts in the vestibular system?

Answer 63

The axes of hair cells in complementary semicircular ducts are opposite, allowing for simultaneous detection of head movements and balance.

Question 64

Explain the role of equilibrium information in maintaining balance.

Answer 64

Equilibrium information is sent to reflex centers in the brain stem, enabling fast, reflexive responses to maintain balance and prevent falls.