Vestibular System

Which receptive organ(s) of the vestibular labyrinth (if any) contain an otolithic membrane?

• Utricle

• Ampulla

• Saccule

• Organ of Corti

• None of these options

Answer explanation

QUESTION:

Which receptive organ(s) of the vestibular labyrinth (if any) contain an otolithic membrane?

ANSWER:

The utricle and saccule are both "otolithic organs"; they each contain a membrane embedded with "otoliths" that produces shearing forces upon hair cells in response to linear acceleration or static changes in head position.

Ampullae have a gelatinous membrane, called the cupula, that is not embedded with any otoliths. The cupula is deflected by movement of endolymph to sense rotational motion.

The Organ of Corti senses vibrations and converts that physical stimulus into impulses that are perceived as sound, not bodily movement/position.

The left and right horizontal canals detect information in what direction?

• Linear acceleration to the left or right

• Rotational acceleration about the midline of the head/body

• Linear acceleration up or down

• Static tilt of the head to the left or right

Answer explanation

QUESTION:

The left and right horizontal canals detect information in what direction?

ANSWER:

The left and right horizontal canals detect rotational acceleration about the midline of the head/body.

Linear acceleration and head tilts are detected by otolithic membranes housed in the utricle or saccule.

Which vestibular nucleus receives input predominantly from otolithic organs?

• Superior

• Medial

• Lateral

• Descending/Inferior

Answer explanation

QUESTION:

Which vestibular nucleus receives input predominantly from otolithic organs?

ANSWER:

Descending/inferior nucleus predominantly receives inputs from the otolithic organs, which is consistent with its role in the regulation of balance and posture.

Other nuclei receive mixed inputs from otolithic organs and semicircular canals to support quick reflexes (VOR when head is in motion, extension of anti-gravity muscles in response to trip/fall)

Which cranial nerve nucleus/nuclei is/are not involved in the VOR?

• Vestibular

• Optic

• Oculomotor

• Facial

• Abducens

Answer explanation

QUESTION:

Which cranial nerve nucleus/nuclei is/are not involved in the VOR?

ANSWER:

Optic nerve and facial nerve are not involved in the VOR;

The optic nerve carries visual information from the retina while the facial nerve controls muscles of the face, but not extra-ocular muscles that move the eyeballs.

The abducens and oculomotor nerves do control the movements of the eye and the VOR coordinates these movements using information about movement the head provided by the vestibular nucleus.

An inability to properly integrate vestibular input with oculomotor responses leads to clinically observable, pathological nystagmus and self-reports from the patient that their visual field is “moving”. What condition would the clinician diagnose in response to these symptoms?

• Vertigo

• Oscillopsia

• Achromatopsia

• Hemianopsia

• Akinetopsia

Answer explanation

QUESTION:

An inability to properly integrate vestibular input with oculomotor responses leads to clinically observable, pathological nystagmus and self-reports from the patient that their visual field is “moving”. What condition would the clinician diagnose in response to these symptoms?

ANSWER:

Oscillopsia is a visual disturbance in which objects in the visual field appear to oscillate.

Patients with vestibular damage may experience vertigo, which is a false sense of rotation, but this is not an accurate description of the visual nature of the symptom being referenced here.

Achromatopsia is a loss of color vision.

Hemianopsia is a loss of vision in half of your visual field of one eye or both eyes.

Akinetopsia is an ability to perceive motion in the visual associated due to cortical damage.