ACTIVE RECALL: VESTIBULAR SYSTEM

VESTIBULAR SYSTEM OVERVIEW

What are the three main functions of the vestibular system?
What is the difference between angular acceleration and linear acceleration?
Which structures detect angular acceleration?
Which structures detect linear acceleration?
Does the vestibular system directly detect constant velocity?
How does the vestibular system help maintain stable vision?
How does the vestibular system contribute to spatial orientation?

2. VESTIBULAR LABYRINTH ANATOMY

Where is the vestibular labyrinth located?
What are the three main vestibular sensory structures?
What is the difference between the bony and membranous labyrinth?
What fluid fills the membranous labyrinth?
What fluid surrounds the membranous labyrinth?
What is the difference between endolymph and perilymph?
Which cranial nerve carries vestibular sensory information?
Where are the cell bodies of primary vestibular sensory neurons located?
Where do primary vestibular neurons project?

3. SEMICIRCULAR CANALS

☐ How many semicircular canals are there, and how are they oriented?
☐ What type of movement do the semicircular canals detect?
☐ What is the ampulla?
☐ What is the crista?
☐ What are hair cells?
☐ What are stereocilia?
☐ What is the kinocilium?
☐ What is the cupula?
☐ What fluid surrounds the cupula?

4. TRANSDUCTION OF ANGULAR ACCELERATION

☐ What happens to the endolymph when the head first begins rotating?
☐ Why does the endolymph initially lag behind head rotation?
☐ How does endolymph movement cause hair-cell stimulation?
☐ What happens when stereocilia bend toward the kinocilium?
☐ Which ion enters the hair cell during depolarization?
☐ What happens to glutamate release during depolarization?
☐ How does depolarization affect vestibular afferent firing frequency?
☐ What happens when stereocilia bend away from the kinocilium?
☐ How does hyperpolarization affect glutamate release?
☐ How does hyperpolarization affect vestibular afferent firing frequency?
☐ Why do vestibular neurons fire even when the head is stationary?
☐ What is the push-pull arrangement between the two ears?
☐ Why does sustained constant rotation eventually produce a reduced semicircular canal response?

5. OTOLITH ORGANS

☐ What are the two otolith organs?
☐ What type of stimulus do the otolith organs detect?
☐ What is the macula?
☐ What is the otolithic membrane?
☐ What are otoconia made of?
☐ Why are otoconia important for detecting movement?
☐ Which otolith organ is especially sensitive to horizontal acceleration?
☐ Which otolith organ is especially sensitive to vertical acceleration?
☐ In which plane is the utricular macula oriented?
☐ In which plane is the saccular macula oriented?
☐ How does head tilt cause hair-cell stimulation?
☐ How does linear acceleration cause hair-cell stimulation?
☐ What is direction selectivity?
☐ Why do hair cells have different preferred directions?
☐ Why can the otolith organs not always distinguish head tilt from linear acceleration independently?

6. CENTRAL VESTIBULAR PATHWAYS

☐ Where do primary vestibular neurons project in the brain?
☐ What additional sensory information reaches the vestibular nuclei?
☐ What are the two major roles of the vestibular system?
☐ What is a premotor neuron?
☐ What are the four major projection targets of the vestibular nuclei?
☐ How does the vestibular system produce rapid reflexes?
☐ How does the vestibular system contribute to conscious spatial orientation?

7. VESTIBULO-OCULAR REFLEX (VOR)

☐ What is the purpose of the VOR?
☐ In what direction do the eyes move relative to the head?
☐ Trace the basic neural pathway of the VOR.
☐ What is the role of the medial vestibular nucleus?
☐ What is the role of the abducens nucleus (CN VI)?
☐ What is the role of the oculomotor nucleus (CN III)?
☐ Which muscle moves the eye inward?
☐ Which muscle moves the eye outward?
☐ If the head turns left, in which direction do the eyes move?
☐ Which extraocular muscles contract during a leftward head turn?
☐ What is physiological nystagmus?
☐ What is the difference between the slow and fast phases of nystagmus?
☐ How is the direction of nystagmus named?
☐ What is caloric testing used for?
☐ What does COWS mean in caloric testing?
☐ What is the expected fast-phase direction after cold-water irrigation of the left ear in an awake person?
☐ What is the expected fast-phase direction after warm-water irrigation of the left ear in an awake person?
☐ How can caloric testing help identify vestibular pathway dysfunction?

8. VESTIBULOSPINAL PROJECTIONS

☐ What is the general function of vestibulospinal pathways?
☐ What is the function of the medial vestibulospinal tract?
☐ Which vestibular nucleus gives rise to the medial vestibulospinal tract?
☐ Which muscles are primarily influenced by the medial vestibulospinal tract?
☐ What is the vestibulocervical reflex (VCR)?
☐ What is the function of the lateral vestibulospinal tract?
☐ Which vestibular nucleus gives rise to the lateral vestibulospinal tract?
☐ Which side of the spinal cord does the lateral vestibulospinal tract primarily influence?
☐ How does the lateral vestibulospinal tract help prevent falling?
☐ What is the vestibulospinal reflex (VSR)?
☐ How do the medial and lateral vestibulospinal tracts differ?

9. VESTIBULOCEREBELLAR PATHWAY

☐ What is the vestibulocerebellum?
☐ What connections exist between the vestibulocerebellum and vestibular nuclei?
☐ How does the vestibulocerebellum integrate vestibular signals with voluntary movement?
☐ Why is it important to distinguish passive movement from self-generated movement?
☐ What is vestibular plasticity?
☐ How can cerebellar plasticity change VOR gain?
☐ Why is the cerebellum important after vestibular damage?

10. VESTIBULAR PATHWAYS TO THE CORTEX

☐ How does vestibular information reach the cerebral cortex?
☐ What is the role of the ventroposterior thalamic nucleus?
☐ Why are vestibular cortical areas considered multisensory?
☐ What is the parieto-insular vestibular cortex (PIVC)?
☐ What other sensory inputs reach the PIVC?
☐ What functions are associated with the PIVC?
☐ What changes in perception can result from PIVC lesions?
☐ What is the difference between personal and extrapersonal space?

11. VESTIBULAR DYSFUNCTION

☐ What is labyrinthitis?
☐ How can trauma to the labyrinth or vestibular nerve affect balance?
☐ What causes benign paroxysmal positional vertigo (BPPV)?
☐ Why can displaced otoconia produce vertigo?
☐ What is Ménière’s disease associated with?
☐ What symptoms can occur in Ménière’s disease?
☐ What is vertigo?
☐ What is tinnitus?
☐ What is spontaneous nystagmus?
☐ Why can acute unilateral vestibular dysfunction cause spontaneous nystagmus?
☐ Why can unilateral vestibular dysfunction cause nausea and vertigo?
☐ How does bilateral vestibular dysfunction differ from unilateral dysfunction?
☐ Why can vision and proprioception compensate for reduced vestibular input?
☐ What is vestibular compensation?
☐ How does neural plasticity contribute to recovery?

12. APPLICATION AND INTEGRATION QUESTIONS

☐ A person turns their head to the right. Explain how the semicircular canals detect this movement.
☐ Explain the complete sequence from hair-cell bending to an increase in vestibular neuron firing.
☐ Explain the complete sequence from hair-cell bending to a decrease in vestibular neuron firing.
☐ A person tilts their head forward. Which vestibular structures contribute to detecting this change?
☐ A person accelerates forward in a car. Which sensory organs detect the acceleration?
☐ Explain why the eyes move opposite to the head during the VOR.
☐ Explain why vestibular dysfunction on one side can cause nystagmus even when the head is still.
☐ Compare the sensory transduction mechanisms of the semicircular canals and otolith organs.
☐ Explain how the vestibular system maintains both gaze stability and posture.
☐ Explain how vestibular, visual and proprioceptive information work together to maintain balance.
☐ Explain how the vestibulocerebellum helps the nervous system adapt after vestibular damage.
☐ Predict the major symptoms expected from damage to both vestibular labyrinths.
☐ Explain why damage to the PIVC can alter spatial perception.
☐ Compare the role of vestibular reflexes with the role of vestibular cortical pathways.

13. FINAL RAPID-FIRE RECALL

Without looking at your notes, complete these statements:

Semicircular canals detect __________.
The utricle is especially sensitive to __________ acceleration.
The saccule is especially sensitive to __________ acceleration.
The sensory epithelium of the semicircular canals is the __________.
The sensory epithelium of the otolith organs is the __________.
The gelatinous structure in the semicircular canals is the __________.
The crystals on the otolithic membrane are called __________.
Hair-cell depolarization increases __________ release.
Hair-cell depolarization increases vestibular afferent __________.
The VOR moves the eyes __________ to head movement.
The slow phase of nystagmus is the __________ phase.
The medial vestibulospinal tract primarily controls __________.
The lateral vestibulospinal tract helps control __________ and __________ activity.
The vestibulocerebellum contributes to motor coordination and __________.
Vestibular information reaches the cortex through the __________.
BPPV is caused by displaced __________.
Ménière’s disease is associated with abnormal __________ regulation.
Neural adaptation after vestibular damage is an example of __________.