Week 4 auditory objective 3

Question 1

components of nervous system pathway

Answer 1

1. spiral ganglion of corti
2. dorsal and ventral cochlear nuclei
3. superior olivary nucleus
4. lateral lemniscus nucleus
5. medial geniculate nucleus (thalamus)
6. auditory cortex

Question 2

Where does the decussation occur between right and left pathways?

Answer 2

nerves from the spiral ganglion in the organ of corti synapse and decussate in the trapezoid body in medulla

Question 3

What is the relationship between the auditory tracts and the RAS?

Answer 3

collateral fibers from auditory tracts pass directly into reticular activating system of the brain stem

this system projects upward into brain and downward into brainstem, activating system in response to a loud sound

Question 4

Where is the auditory cortex?

Answer 4

principally on the supratemporal plane of the superior temporal gyrus, and extends to the lateral side of the temporal lobe

Question 5

How does a person determine the direction from which sound comes?

Answer 5

horizontal direction determined two ways:

1. the time lag between sound entry into one ear and its entry into the opposite ear

• best at freq under 3000 cycles per second
• much more accurate than second mechanism

2. the different intensities between those two sounds

Front/behind determination: achieved by pinnae of the two ears, which changes quality of the sound by emphasizing specific sound frequencies

Question 6

Neural analysis for the detection processs

Answer 6

medial superior olivary nucleus (MON) —> lateral superior olivary nucleus (LON)

LON- compares difference in intensities
MON- detects time lag