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IMED3001 > Physiology of Hearing and Balance > Flashcards

Physiology of Hearing and Balance Flashcards

1
Q

What is the human hearing range?

A

20 - 20000 Hz

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2
Q

What happens if sound is too loud or too high pitched?

A

It can cause pain or hearing loss

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3
Q

What is the range of frequencies of normal speech?

A

1500 to 5000 Hz where hearing is most sensitive.

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4
Q

What is the loudness of sound that can cause hearing damage?

A

> 90 dB

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5
Q

How are low and high pitch sounds different in their ability to travel long distances?

A

Deeper sounds (lower pitch) tend to move further through surfaces.

Higher pitches lose energy more quickly.

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6
Q

What are the 3 physiological and anatomical parts of the ear?

A

Outer ear (External surface)

Middle ear (ossicles for hearing)

Inner ear (labyrinth) for hearing and equilibrium

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7
Q

What does the eustachian tube do?

A

Pressure equalization by connecting to the naso-pharynx. It is normally closed but can be opened by releasing pressure. (can be done by yawning)

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8
Q

What does the tympanic membrane do?

A

It converts the sound waves to movement which causes bones of the middle ear to move.

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9
Q

What happens in the middle ear?

A

Ossicles articulate to form a lever system that amplifies and trasmits vibrations from tympanic membrane to the inner ear. Oval window converts the mechanical signal to sound again at the inner ear.

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10
Q

What does the oval window do?

A

It converts mechanical energy of the ossicles back into sound energy to be transmitted to the inner ear.

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11
Q

What do the stapedius and tensor tympani do?

A

They attach to stapes and malleus to adjust the loudness of the sound.

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12
Q

What is the tympanic reflex?

A

Loud sound causes tensor tympani and stapedius to contract + limit vibration and dampen the noise.

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13
Q

What are the parts of the inner ear?

A

Cochlea - Hearing - Organ of Corti hair cells

Vestibule - static equilibrium - macula hair cells

Semicircular canals - dynamic equilibrium - crista ampularis hair cells

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14
Q

What are the contents of the membranous labyrinth?

A

It is filled with endolymph (similar to intracellular fluid with high [K+])

It floats in perilymph which is similar to cerebrospinal fluid.

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15
Q

What is the membranous labyrinth?

A

Fleshy tubes lining bony labyrinth

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16
Q

Why is the high [K+] content of the inner ear important?

A

Due to the use of K+ channels for hearing.

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17
Q

What hair cells are involved in hearing?

A

Organ of corti

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18
Q

What hair cells are involved in static equilibrium?

A

Macula hair cells

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19
Q

What hair cells are involved in dynamic equilibrium?

A

Crista ampularis

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20
Q

What nerve do the structures of the inner ear feed into?

A

CNVIII (Vestibulocochlear nerve)

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21
Q

What does the organ of corti look like?

A

A long tube that is coiled from the oval window to the end of the spiral.

The tube is divided into 3 separate compartments (The scala vestibuli, the scala tympani, and the scala media)

Scala media contains the receptors for hearing. the scala vestibuli and scala tympani are important for moving waves through the organ of corti.

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22
Q

Where are receptors for hearing located?

A

In the scala media of the organ of corti.

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23
Q

What are hair cells?

A

They are long cells that extend from the membrane and are connected directly to nerves. They contain outer hair cells (Potassium channels) called stereocilia. They have potassium channels.

When they are physically moved they transduce signals.

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24
Q

What are the types of hair cells?

A

Outer and inner hair cells

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25
Q

How is scala media separated from scala vestibuli and scala tympani?

A

Separated from scala vestibuli by thin vestibular membrane.

Separated from scala tympani by thicker basilar membrane.

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26
Q

Why is the membrane between scala media and scala tympani thick?

A

It contains all the receptors and structures needed for signal transduction.

27
Q

What is the membrane between scala media and scala tympani called?

A

Basilar membrane

28
Q

What is the membrane between the scala media and scala vestibuli called?

A

Vestibular membrane

29
Q

Which window is involved in sound transduction?

A

Oval window

30
Q

How does sound get transmitted from oval window to the hair cells?

A

The oval window is hit continuously by middle ear bones and the sound travels through the scala vestibuli which transmits sound through the thin vestibular membrane to the scala media where the hair cells can transmit the signal.

31
Q

Which hair cells are important for hearing?

A

Inner hair cells

32
Q

What do outer hair cells do?

A

They adjust sensitivity of basilar membrane to make it more or less solid based on incoming sound.

33
Q

How do outer hair cells carry out their functions?

A

They make the basilar membrane more or less tense.

They can amplify sounds.

34
Q

What kind of potassium channels do hair cells have?

A

Mechanically gated potassium channels.

35
Q

How is sound interpretted by hair cells?

A

Vibration moves the hair cells opening potassium channels resulting in depolarization of cell and release of neurotransmitter. These cells are opened and closed at the frequency of the sound which correlates to the frequency of action potentials produced as a result.

36
Q

Where in the brain does sound perception go?

A

High or low pitched part of our cortex depending on the sound

37
Q

How is loudness coded for by sensory receptors?

A

Loudness depends on intensity of cochlear vibrations and louder sounds make basilar membrane vibrate more vigorously which triggers high frequency of action potentials. This is interpretted by the brain as a louder sound.

38
Q

How is pitch coded for by sensory receptors?

A

Low frequencies penetrate further into the organ of corti so brain interprets pitch as lower. (geographic location of hair cells)

39
Q

How is the basilar membrane optimized for low frequency sensation?

A

Basal end is stiff and distal end is flexible.

40
Q

Why are there so many outer hair cells when inner hair cells do all the sensing of sound?

A

They increase sensitivity and specificity to sound frequencies.

They amplify sound by reverse transduction (outer hair cells generate movement amplifying weak signals)

Electro-mechano transduction: Excitation activates a motor protein (prestin)

Local area effect of loosening or tensing the basilar membrane. (frequency specific)

41
Q

Which part of the brainstem is involved in the reflex of moving head towards loud sounds?

A

The inferior coliculi

42
Q

What is the pathway for auditory sensation?

A

Cochlea interprets sound which sends fibers to the cochlear nucleus which sends information to the inferior colliculi. The inferior colliculi of the midbrain then transmit a signal to the thalamus before reaching the auditory cortex. The primary auditory cortex then feeds into association cortices (Wernicke’s area)

Information that goes to inferior colliculi can also create a reflex arc with neck muscles.

Tympanic reflex also goes from the inferior colliculi.

43
Q

How is the auditory information mapped onto the auditory cortex?

A

Laterally lower frequency sounds and medially higher frequency sounds.

44
Q

What auditory reflexes pass through the inferior colliculi?

A

Head turning auditory reflex

Tympanic reflex

45
Q

What can cause hearing loss?

A

Sensorineural factors

Conductive causes (blockage, damage, infection)

46
Q

What causes sensorineural hearing loss?

A

Permanent (caused by age, noise, or frequency)

Sensory (caused by cochlea hair cells)

Neural (caused by the cochlea nerve path)

47
Q

What causes conductive hearing loss?

A

Loss of sound conduction via middle/outer ear

Blockage drainage or infection (otitis media)

48
Q

Which of the types of hearing can be repaired?

A

Conductive hearing loss

49
Q

What is equilibrium? What is unique about equilibrium?

A

Coordination, balance and orientation in 3-dimensional space.

It is the only special sense where information mostly goes to lower brain centers.

50
Q

What is static equilibrium?

A

The perception of the orientation of the head when the body is stationary.

51
Q

What is dynamic equilibrium?

A

Perception of motion or acceleration.

52
Q

What are the 2 chambers of the vestibular apparatus and where are they relative to each other?

A

Saccule is anterior and utricle is posterior.

53
Q

What is the function of the saccule and utricle?

A

Responsible for static equilibrium and linear acceleration

54
Q

How is rotational acceleration detected?

A

3 semicircular ducts

55
Q

What do the utricle and saccule contain that is important for perception of equilibrium?

A

A macula. (An otolith (made of calcium carbonate) sitting on top of some hair cells)

56
Q

How are semicircular canals arranged?

A

Each canal lies in one of 3 planes and they sense rotational acceleration of the head.

57
Q

How do semicircular canals work?

A

Acceleration moves the fluid in opposite direction and this triggers bending of hair cells which opens potassium channels under the hair cells after being projected to the brain.

58
Q

What are the 5 target pathways of vestibular projection?

A

Cerebellum

Nuclei of oculomotor, trochlear, and abducens nerve to produce vestibulo-ocular reflex

Reticular formation

Spinal cord

Thalamus

59
Q

What does the cerebellum do with vestibular information?

A

Integrates vestibular information into its control of head and eye movements, muscle tone, and posture

60
Q

What is the vestibulo-ocular reflex?

A

The reflex which keeps vision fixed on a distant object while walking.

61
Q

What does the reticular formation do with vestibular information?

A

Thought to adjust blood circulation and breathing to postural changes.

62
Q

What does the spinal cord do with vestibular information?

A

Descends through vestibulospinal tracts and innervates antigravity muscles

63
Q

What does the thalamus do with vestibular information?

A

Thalamic relay to cerebral cortex for awareness of position and motor control of head and body

64
Q

What causes vertigo?

A

Peripheral factors include vestibular issues or benign proxysmal positional vertigo (BPPV) where calcium deposits in semicircular canals and this results in 32% of all vertigo.

Central reasons are usually related to the pathways, the brainstem nuclei, or the cerebellum.

IMED3001 (46 decks)

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