Auditory System Flashcards

Question 1

Q

Where does the nerve come in contact with the cochlear duct?

What is the Stria Vascularis? What does it do?

What is the Spiral Organ?

What type of cells are hair cells?

What are the inner and outer hair cells for?

Which neurotransmitter is used between the hair cells and afferent nerves?

What can destroy the stereocilia?

Answer

A

Cochlear branch of Vestibulocochlear nerve (CN VIII) is in contact with the Tectorial membrane
Lateral wall of cochlear duct; exchanges ions between blood and endolymph to create HIGH K+ IN ENDOLYMPH
Outer hair cells and an Inner hair cell; has little Stereocilia on their ends
Highly specialised, AXONLESS receptors
o Inner hair cells; for sound discrimination
o Outer hair cells; sound changes its length, amplifies
the sound by moving the Tectorial membrane
GLUTAMATE
Irreversible OTOTOXICITY by certain drugs

Question 2

Q

How the ear detects sound?
1. How do the sound waves reach the 3 ossicle bones?

What do the bones do?

How does this lead to depolarisation?

What is the condition called where there’s failure to transmit sound waves?

What is Endolymphatic Hydrops?

Answer

A

Sound waves vibrate the Tympanic membrane, and the vibrations are transmitted along the 3 small bones (Ossicles) behind it; causes the Fluid in the inner ear to vibrate
Amplify the sound
Vibrations of fluid spreads to the Cochlea; first goes through Scala Vestibuli and transmits through the flexible middle membrane to go through Scala Tympani
Both the Basilar and Tectorial membrane vibrate, causing the movement of the Stereocilia back and forth
Mechanically-gated K+ channels open as the longer Stereocilia pull away from the shorter ones; causes the leakage of K+ INTO cell = Depolarisation
o Endolymph has a RMP of +80mV
Conductive Hearing Loss
Endolymph Production > Removal; ↑Pressure in cochlear duct, causing damage

Question 3

Q

Loudness:
How is it encoded?

What can cause Noise-induced Hearing Loss?

Pitch:
How is it encoded?

Why do we get Presbycusis as we age?

Answer

A

• Larger vibrations
• Bigger receptor potentials
• More Transmitter release
• More Action Potentials
Overstimulated hair cells kill their afferents, Large vibrations damage Stereocilia and kill hair cells

• Each pitch activates a certain set of receptors
• Outer coil = Higher frequency (20khz); base of cochlea
• Inner coil = Lower frequency (20hz); apex of cochlea
High pitched sound is more energetic and damaging, so, over time, we lose high-frequency hearing

Question 4

Q

Primary Auditory Pathway/A1:
What is it for?

Where is it?

Discriminative hearing:
What pathway is taken from the cochlear to reach the A1?

How is frequency arranged in the A1?

What can damage the Cochlear nerve?

What can damage to the key areas that decode speech cause?

Sound Localisation:
What pathway is taken from the cochlear to reach the A1?

What are the 2 types of Superior Olivary Nuclei? What does each do? What type of sound does is it for?

Which of the 2 sounds can be compared unambiguously?

Answer

A

1. Cochlear nerve synapses onto Cochlear Nuclei in Medulla
  1. Second-order neurons decussate and ascend to the Inferior Colliculus, then to the Medial Geniculate Nucleus (Thalamus)
  2. Third-order neurons go to the A1
High frequency at the back, Low frequency at the front
Acoustic Neuroma (Space-occupying Lesion)
Dysphasia

1. Cochlear nerve synapses onto Cochlear Nuclei in Medulla
  1. Second-order neurons go to the opposite SUPERIOR OLIVARY NUCLEUS
  2. Ascend to Inferior Colliculus, then Medial Geniculate Nucleus; third-order neurons to A1
• MEDIAL superior olivary nucleus; Compares TIMING of when sound reaches both ears
o Only for LOW-frequency sounds
• LATERAL superior olivary nucleus; Compares LOUDNESS of sound in both ears
o Only for HIGH-frequency sounds
Low-frequency sounds

(4 cards)