WEEK 8 - Topic 18 - Auditory Pathway and Processing

Question 1

Outline the auditory pathway to the brain

Answer 1

1. Impulses generated in the cochlea pass via the spiral ganglion, and along the afferent fibres of the cochlear nerve to the cochlear nuclei of the medulla.
2. From there, impulses are sent to the superior olivary nucleus, which lies at the junction of the medulla and pons.
3. The impulses then travel to the inferior colliculus (auditory reflex centre in the midbrain).
4. Impulses then pass to the primary auditory cortex in the temporal lobe, which provides conscious awareness of sound.

Question 2

Why is the auditory pathway unusual?

Answer 2

The auditory pathway is unusual because not all of the fibres decussate to the other side of the brain. For this reason, each auditory cortex receives impulses from both ear.

Question 3

What accompanies louder sound?

Answer 3

• Larger movements of the basilar membrane
• Larger deflections of the hairs on the hair cells
• Larger graded potentials in the hair cells
• More neurotransmitter released
• More frequent APs generated

Question 4

What is responsible for localising sound?

Answer 4

Mostly the superior olivary nuclei (which lies at the junction of the medulla and pons)

Question 5

When sound comes from one side, what happens?

Answer 5

When sound comes from one side, it activates the receptors of the nearer ear earlier and more vigorously.

Question 6

What allows you to discriminate sounds and separate tones?

Answer 6

A person is able to hear two separate and distinct tones whenever the difference between sound wavelengths is sufficient for discrimination

Question 7

What determines pitch?

Answer 7

Sound waves of different frequencies activate hair cells in different positions along the length of the basilar membrane and impulses from specific hair cells are interpreted as specific pitches.