Physiology of Hearing

Question 1

what is the speed of sound?

Answer 1

340ms

Question 2

what is the range of sound frequency heard by humans?

Answer 2

20Hz - 20,000Hz

Question 3

what dictates pitch?

Answer 3

frequency - greater frequency = higher pitch, lower frequency = lower pitch

Question 4

what dictates volume?

Answer 4

amplitude - : low amplitude = low volume, high amplitude = high volume

Question 5

what are the 3 parts of the ear?

Answer 5

external, middle, and inner ear

Question 6

what is the role of the external ears role?

Answer 6

receiver - funnels sound down into the external acoustic meatus

Question 7

what is the role of the middle ear?

Answer 7

amplifier

Question 8

how does the middle ear transmit sound to the inner ear?

Answer 8

Sound wavers collide with the tympanic membrane
Push back and forth – passes these vibrations onto tiny bones in middle ear
Together form a chain that conducts vibrations to the oval window

Question 9

what is the tympanic membrane:OW ratio?

Answer 9

18:1

Question 10

what is the eustachian tube?

Answer 10

• Ventilation pathway for middle ear mucosa

Question 11

what is the role of the inner ear?

Answer 11

transduction

Question 12

what are the 2 layers of the inner ear?

Answer 12

• Bony labyrinth – fluid filled system

* Membranous labyrinth – continues series of sacs and ducts inside bony labyrinth

Question 13

what is the structure of the cochlea?

Answer 13

• Scala vestibuli (perilymph), scala media, scala tympani
• SM between SV and ST
• Basilar membrane – stiff band of tissue that runs between the SM and ST

Question 14

how is sound transduced in the inner ear?

Answer 14

Ossicle bones send pressure waves up fluid, cause basilar membrane to move Transduction occurs when membrane moves, (bending force) causing movement of hairs on cochlea
Depolarisation towards
Hyperpolarisation away.
Electrical impulses travel from organ of Corte along cochlear nerve, along the auditory pathway to the auditory cortex

Question 15

what are the systems involved in balance?

Answer 15

• Visual (central important)
• Cardiovascular
• Proprioceptive
• Vestibular
• Vestibulospinal tract
• Vestibulo-ocular reflex

Question 16

what are the vestibular end organs?

Answer 16

• Found in the inner ear
• otolith organs: utricle & saccule
• semi-circular canals: lateral, posterior and inferior

Question 17

what are the semi-circular canals

Answer 17

• Orientation at 90 degrees to each other so paired, equal and opposite
o X axis – going through nose to back of head
o Y axis – ear to ear
o Z axis – Vertical

Question 18

what are the otolith organs?

Answer 18

utricle & saccule

Question 19

how do the semi circular canals work?

Answer 19

Filled with a fluid called endolymph and when we rotate along a certain plane it causes the fluid to shift in the semi circular canal – so we know which

Question 20

how do otolith organs work?

Answer 20

Maculae of these organs have stereocilia projecting upwards into a gelatinous matrix with otoconia
Contain calcium carbonate crystals attached to hair cells in a gel substance
Position changes cause crystals to move and they pull on hair
Brain perceives movement

Question 21

what are the central pathways of balance?

Answer 21

• Complex series of communications in vestibular nuclei with outputs to
• Vestibulospinal tract rep - motor output to the neck, back and leg muscles.
• Medial longitudinal fasciculus & ocular muscles - motor output to eyes
• Medial lemniscus & thalamus to cerebrum