The Auditory System

Question 1

Where are the cell bodies for the auditory part of this nerve?
A. Otic ganglion.
B. Nodose ganglion.
C. Vestibular nuclei.
D. Spiral ganglion.
E. Cochlear Nuclei.

Answer 1

Spiral ganglion

The spiral ganglia contain the cell bodies for the primary auditory axons. This ganglion is homologous to a dorsal root ganglion of the spinal cord. .

Question 2

Tumors originating from the Schwann cells of CN VIII (acoustic neuromas) are not uncommon. As the tumor grows, it not only compresses VIII but also encroaches upon adjacent cranial nerves. What cranial nerve close to VIII is likely to be involved? Choose one.
A. IX and X.
B. VII.
C. V.
D. VI.

Answer 2

VII.

CN VII is immediately adjacent to CN VIII. The tumor is on the left side and is seen as a round white object.

Question 3

This artery supplies the Visual Cortex. Which one is it?
A. Anterior Cerebral Artery.
B. Middle Cerebral Artery.
C. Posterior Cerebral Artery.

Answer 3

Posterior Cerebral Artery

The auditory cortex is located along the upper border of the temporal lobe inside the lateral fissure. It is supplied by the middle cerebral artery. This arteriogram is of the posterior cerebral artery in an lateral view.

Question 4

The receptors in the Organ of Corti are hair cells. How are they stimulated?
A. By air-borne waves.
B. Displacement of the vestibular membrane.
C. Displacement of the basilar membrane.
D. Displacement of the tectorial membrane.

Answer 4

Displacement of the basilar membrane

The displacement of the basilar membrane stimulates the hair cells of the auditory system by deflecting the cilia that are embedded in the tectorial membrane.

Question 5

Which of the following is the lowest level at which “BINAURAL” input to the same neuron occurs?
A. Hair Cells.
B. Spiral Ganglion Cells.
C. Cochlear Nuclei.
D. Superior Olivary Nuclei.
E. Inferior Colliculus.

Answer 5

Superior Olivary Nuclei

The superior olivary nucleus is an ``auditory relay nucleus’’ that receives input from cochlear nuclei on both sides of the brain stem. These neurons play a role in the localization of sound by comparing the time delay between impulses coming from each ear.

Question 6

Cranial nerves VII and VIII pass through the:
A. Stylomastoid foramen.
B. Jugular foramen.
C. Internal auditory meatus.
D. Oval foramen.

Answer 6

Internal auditory meatus.

Question 7

Branches of which cerebral artery vascularize the primary auditory cortex, Wernicke’s area, and the angular gyrus?
A. Thalamogeniculate.
B. Anterior Choroidal.
C. Middle Cerebral.
D. Posterior Cerebral

Answer 7

Middle Cerebral.

Question 8

Where is the dorsal root ganglion of the auditory portion of VIII ?
A. In the medulla.
B. In the bony spiral lamina.
C. In the internal auditory meatus.
D. In the facial canal.

Answer 8

In the bony spiral lamina

The cochlear duct winds around the bony spiral lamina in the petrous part of the temporal bone. Within this part of the bone reside the cell bodies of the auditory axons. This ganglion is therefore named the spiral ganglion. The bone is blue on this section. The nerve is dark pink in the center.

Question 9

Unilateral Cerebral strokes can cause deficits in motor control, somatic sensation and vision. However, they do not cause deficits in hearing. The explanation for this is:
A. Auditory information does not reach the cortex
B. Auditory information only goes to one hemisphere.
C. Auditory information goes to both hemispheres

Answer 9

Auditory information goes to both hemispheres