Auditory and Vestibular Systems

Question 1

What cranial nerve is associated with audition and equilibrioception?

Answer 1

CN 8 (Vestibulocochlear nerve)

Question 2

What are the three main components of audition (hearing)?

Answer 2

Outer ear, middle ear, cochlea

Question 3

What are the two main components of equilibrioception (balance)?

Answer 3

Vestibule, semicircular canals

Question 4

What are the sensory receptor cells for hearing and balance?

Answer 4

Hair cells

Question 5

What type of receptors are hair cells?

Answer 5

Mechanoreceptors

Question 6

What are the hair-like projections on hair cells called?

Answer 6

Stereocilia and kinocilia

Question 7

Where are hair cells for audition located?

Answer 7

Spiral organ of Corti (in the cochlea)

Question 8

Where are hair cells for balance located?

Answer 8

Maculae (of saccule/utricle) and Cristae ampullaris (of semicircular canals)

Question 9

What structure contains the cell bodies of the 1st-order auditory neurons?

Answer 9

Spiral ganglion

Question 10

Where is the spiral ganglion located?

Answer 10

Within the modiolus (core) of the cochlea

Question 11

Where do the 1st-order auditory neurons (from spiral ganglion) synapse?

Answer 11

Cochlear nuclei (dorsal and ventral)

Question 12

Where are the 2nd-order auditory neurons located?

Answer 12

In the cochlear nuclei

Question 13

At what junction does CN 8 attach to the brainstem?

Answer 13

Pons-medulla junction

Question 14

What is the function of the superior olivary nuclei (SON)?

Answer 14

Compares signals from both ears for sound directionality (binaural hearing)

Question 15

How do signals from the ventral cochlear nucleus reach the contralateral SON?

Answer 15

Via the trapezoid body (ventral acoustic stria)

Question 16

The SON projects to nuclei of which two cranial nerves for reflexes?

Answer 16

CN 5 (Trigeminal) and CN 7 (Facial)

Question 17

What is the purpose of the auditory reflexes involving middle ear muscles?

Answer 17

Protect the cochlea from loud sounds by limiting ossicle movement

Question 18

What is the efferent limb for the tensor tympani reflex?

Answer 18

V3 (Mandibular division of CN 5)

Question 19

What is the efferent limb for the stapedius reflex?

Answer 19

CN 7 (Facial nerve)

Question 20

What tract ascends from the superior olivary nuclei?

Answer 20

Lateral lemniscus

Question 21

Where does the lateral lemniscus primarily project?

Answer 21

Inferior colliculus

Question 22

What are three functions of the inferior colliculus?

Answer 22

Locate sound origin, process pitch fluctuations, mediate startle response

Question 23

Lesions in the inferior colliculus are known to cause what condition?

Answer 23

Tinnitus

Question 24

Where does the inferior colliculus project?

Answer 24

Medial geniculate body (nucleus) of the thalamus

Question 25

What tract connects the inferior colliculus to the thalamus?

Answer 25

Brachium of the inferior colliculus

Question 26

Where does the auditory pathway terminate (primary cortex)?

Answer 26

Auditory cortex in the superior temporal gyrus (and transverse temporal gyri)

Question 27

What are the Brodmann areas for the primary auditory cortex?

Answer 27

BA 41 and BA 42

Question 28

Why is a unilateral lesion in the ascending pathway unlikely to cause complete deafness on one side?

Answer 28

Frequent decussation (crossing over) of fibers

Question 29

What is sensorineural hearing loss?

Answer 29

Hearing loss due to damage to the cochlea, spiral ganglion, or CN 8

Question 30

What is conductive hearing loss?

Answer 30

Hearing loss due to damage to the middle or external ear

Question 31

What are the two types of sensory organs in the vestibular system?

Answer 31

Otolith organs and Semicircular canals

Question 32

What are the two otolith organs?

Answer 32

Saccule and Utricle

Question 33

What is the sensory receptor within the otolith organs?

Answer 33

Macula

Question 34

What are the three semicircular canals?

Answer 34

Anterior (superior), Posterior, and Lateral (horizontal)

Question 35

What is the sensory receptor within the semicircular canals?

Answer 35

Crista ampullaris (located in the ampulla)

Question 36

How is the crista ampullaris stimulated?

Answer 36

Rotational head movement causes endolymph to lag, bending the cupula/stereocilia

Question 37

Where are the cell bodies of the 1st-order vestibular neurons?

Answer 37

Vestibular ganglia

Question 38

Where do the 1st-order vestibular neurons synapse?

Answer 38

Vestibular nuclei (in the pons and medulla)

Question 39

What are the four vestibular nuclei?

Answer 39

Superior, Inferior, Medial, and Lateral

Question 40

What is the projection of the Lateral Vestibulospinal Tract (LVST)?

Answer 40

Ipsilateral (same side)

Question 41

What is the main function of the LVST?

Answer 41

Excite extensors and inhibit flexors to maintain balance and upright posture

Question 42

What is the projection of the Medial Vestibulospinal Tract (MVST)?

Answer 42

Bilateral (both sides)

Question 43

What is the main function of the MVST?

Answer 43

Neck stability (inhibits neck/upper back muscles)

Question 44

The MVST is part of what larger tract?

Answer 44

Medial longitudinal fasciculus (MLF)

Question 45

How do vestibular signals reach the cerebellum?

Answer 45

Via the inferior cerebellar peduncle

Question 46

What lobe of the cerebellum receives primary vestibular input?

Answer 46

Flocculonodular lobe

Question 47

What is the function of the vestibulo-cerebellar pathway?

Answer 47

Coordination of balance during movement

Question 48

The ascending vestibular pathway to the cerebral cortex allows for what?

Answer 48

Conscious awareness of position and movement

Question 49

What tract coordinates head and eye movements by projecting to CN III, IV, and VI nuclei?

Answer 49

Medial longitudinal fasciculus (MLF)

Question 50

What is the Vestibulo-ocular Reflex (VOR)?

Answer 50

Involuntary, compensatory eye movement during head movement to stabilize gaze

Question 51

In the VOR, if the head rotates right, which way do the eyes move?

Answer 51

Left

Question 52

To move the eyes left (for VOR), which two muscles must contract?

Answer 52

Right medial rectus and Left lateral rectus

Question 53

What is nystagmus?

Answer 53

Involuntary eye movements

Question 54

How is vestibular nystagmus named?

Answer 54

By the direction of the quick, corrective movement (e.g., "right-beating")

Question 55

What is Benign Paroxysmal Positional Vertigo (BPPV)?

Answer 55

Vertigo caused by otoliths (calcium crystals) being dislodged from the maculae and entering a semicircular canal

Question 56

What is it called when otoliths are free-floating in the canal?

Answer 56

Canalithiasis

Question 57

What is it called when otoliths get stuck to the cupula?

Answer 57

Cupulolithiasis