Vestib: Central Anatomy Flashcards
What is the CNS & where does it send its information to?
It is the central processing mechanism
Sends its outputs to the spinal cord and the ocular muscles to generate the VOR
What is the role of the VOR?
- Keeps the eyes steady while the head is moving
- Angular VOR is controlled by the SCCs to allow gaze stabilization
- Linear VOR is controlled by the otoliths to compensate for translation/tilt
What is the role of the VSR?
Prevents falls by maintaining head and postural stability by compensating body movements
When is the VOR most effective?
Between 1-4HZ
List the four retus muscles of the extraocular muscles
- Medial
- Lateral
- Superior
- Inferior
List the two oblique muscles of the extraocular muscles
- Inferior
- Superior
What direction does the SR muscle move?
Intorsion & Elevation
What direction does the IR muscle move?
Abduction & depression
What direction does the MR muscle move?
Adduction
What direction does the IO muscle move?
Extorsion, abduction, and elevation
What direction does the SO muscle move?
Intorsion, abduction, and depression
What direction does the LR muscle move?
abduction
The oculomotor III inervates which muslces?
Contra SR
Ipsi IR
Ipsi MR
Ipsi IO
The trochlear IV inervates which muslces?
Contra SO
The abducens VI inervates which muslces?
Ipsi LR
What is the mnemonic for the nerve supply to the extraocular muscles?
LR6 SO4 O3
0 = other muscles (superior, inferior, medial recti & inferior oblique
Which two ocular eye muscles are innervated from contralateral projections?
SO & SR
When excited, where does the SCC afferent send projections to in the VN first?
Abducens
What is the name of the pathway that helps conjugate eye movements?
Medial Longitudinal Fasiculus (MLF)
When you rotate your head to the left, which eye muslces contract?
MR (left) contracts
LR (right) contracts
When you rotate your head to the right, which eye muslces contract?
MR (right) contracts
LR (left) contracts
Which part of the cerebellum responds to Vestibular stimulation?
Vermis - Cerebellar midline
What parts of the cerebellum are referred to as “Vestibular Cerebellum”
Flocculus
Nodulus
Uvula
Fastigial nucleus
In the cerebellum, what happens if there’s an impairment in the nodulus/uvula (NOD)
- Periodic alternating nystagmus
- Positional downbeat or positional apogeotropic horizontal direction changing nystagmus
In the cerebellum, what happens if there’s an impairment in the Fastigial nucleus (FN)
Hypermetric saccades with Fastigial nucleus lesions
In the cerebellum, what happens if there’s an impairment in the flocculus/paraflocculus (tonsil)
- Downbeat gaze evoked and rebound nystagmus
- Abnormal aplitude and direction of VOR
- Impairment of smooth pursuit and VOR cancellation
In the cerebellum, what happens if there’s an impairment in the oculomotor vernis (OMV)
Hypometric saccades with ocular motor vermis lesions
What does the superior Vestibular artery supply?
Horizontal & Superior SCCs & Utricle
What does the common cochlear artery flow into?
Posterior SCC, Saccule, & Cochlea
Why does nystagmus occur & how is it named?
The imbalance in the Vestibular firing rate
Named according to fast phase
When does nystagmus increases?
During the gaze in the direction of the spontaneous nystagmus and decreases during the gaze in the opposite direction (Alexander’s law)
What happens in an acute unilateral peripheral vestibular impairment?
The spontaneous nystagmus is horizontal, beating away from the lesion side, & toward the more neurally-active side
What can we expect for impaired VOR during head movements?
- Normal VOR for slow/prolonged head rotation
- Normal VOR for quick head rotation toward the normal ear
- Abnormal VOR for quick head rotation toward the lesioned ear
