L5

Question 1

• How are sounds from our environment translated into neural signals?

Answer 1

• Hearing commences with the capture of sound waves by the ear.
• Within the ear, auditory receptors convert the mechanical energy of sounds into an electrical signal, and then that information is transmitted to the brain.

Question 2

what is the Auditory Apparatus

Answer 2

• The ear has three parts:

1. Outer ear
2. Middle ear
3. Inner ear

Question 3

what are sound waves

Answer 3

• Sound is caused by small areas of high and low pressure propagating outward from the source.

Question 4

what makes up the Outer Ear

Answer 4

• Pinna and

* Auditory Canal – ends at the eardrum

Question 5

what is the pina

Answer 5

– a prominent fold of cartilage-supported skin; captures sound and focuses it into the auditory
canal.

Question 6

what makes up the Middle Ear

Answer 6

• Ear drum (or tympanic membrane)

* Ossicles – middle ear bones

Question 7

what happens when sound waves reach the Middle Ear

Answer 7

• When a sound wave reaches the middle ear, a series of high and low pressure regions impinge upon the
eardrum.
• The arrival of a high pressure region pushes the eardrum inward; the arrival of a low pressure region
pulls the eardrum outward.
• The continuous arrival of high and low pressure regions causes the eardrum to vibrate.
• Because the eardrum is attached to the bones in the middle ear, the bones begin vibrating as well. Thus,
the sound signal is transformed into the mechanical vibrations of the bones in the middle ear.
• These vibrations are then transmitted to the fluid of the inner ear via vibration of the membrane at the
oval window.

Question 8

what is the cochlear

Answer 8

• Cochlea – spiral-shaped fluid-filled tube; contains
the hair cells that serve as the receptors for
audition.

Question 9

what is the structure of the inner ear

Answer 9

Cochlea

Question 10

how does the signal get converted from mechanical to electrical

Answer 10

• Within the cochlea, the vibrations produce waves
in the fluid that cause the hair cells to move.
• The hair cells respond by converting the
mechanical signal into an electrical signal.
• Within the cochlea, hair cells synapse on spiral
ganglion cells.

Question 11

what forms the the auditory nerve

Answer 11

The axons of the spiral ganglion cells form the auditory nerve

Question 12

describe the tuning curve of a spiral ganglion cell

Answer 12

• Spiral ganglion cells are tuned to specific frequencies (e.g., a spiral ganglion cell may be maximally sensitive to a sound of 1600 Hz, with the firing rate dropping off rapidly for lower- and higher frequency sounds).

Question 13

what is Tinnitus

Answer 13

• With tinnitus, a person hears noises in the absence of any sound stimulus.
• The subjective sensation can take many forms, including buzzing, humming, and whistling.

Question 14

what causes tinnitus

Answer 14

• You may have experienced temporary tinnitus after listening to loud music.

• Tinnitus is typically caused by disease processes affecting the cochlea or auditory nerve, but it can also
be caused by spontaneous activity.
Inner Ear → CNS

Question 15

what structures are found in the inner ear

Answer 15

• Your inner ear contains structures for both the sense of hearing and the sense of balance.

Question 16

describe the pathway from the cochlea to the brain

Answer 16

• The axons of the spiral ganglion cells exit the cochlea and converge with the axons of vestibular
neurons to form the vestibulocochlear nerve.
• The vestibulocochlear nerve carries nerve impulses for both balance (vestibular nerve) and hearing
(auditory nerve) from the ear to the brain.
• Thus, auditory information travels via the vestibulocochlear nerve to the brain stem.