Question

When the Acoustic Nerve enters the Brain Stem at the level of the Medulla?

A. The nerves connect directly to the Cerebral Cortex

B. most nerves cross to the opposite side and then continue up to the Cerebral Cortex

C. Because they go up via the lateral lemniscus these auditory nerves are able to bypass the Pons, Midbrain and Thalamus

D. Stimulation in the right ear will be processed mainly in the Temporal Lobe of the Right Cerebral Cortex

E. none of the above.

Answer 1

Answer B)Most of the nerves cross to the opposite side and then continue up to cerebral cortex.

Pathway of hearing

1) . The first neurons of the pathway are located in the spiral ganglion. They are bipolar. Their peripheral processes innervate the organ of Corti while the central processes terminate in the dorsal and ventral cochlear nuclei.

2).The second neurons lie in the dorsal and ventral cochlear nuclei. Most of the axons arising in these nuclei cross to the opposite side in Medulla (in the trapezoid body) and terminate in the superior olivary nucleus. (Many fibres end in the nucleus of the trapezoid body or of the lateral lemniscus.) Some fibres are uncrossed

3).The third neurons lie in the superior olivary nucleus. Their axons form the lateral lemniscus and reach the inferior colliculus

4)The fourth neurons lie in the inferior colliculus. Their axons pass through the inferior brachium to reach the medial geniculate body. (Some fibres of the lateral lemniscus reach the medial geniculate body without relay in the inferior colliculus.)

5).The fifth neurons lie in the medial geniculate body. Their axons form the auditory radiation, which passes through the sublentiform part of the internal capsule to reach the auditory area in the temporal lobe .