Week 10 - Vestibular Flashcards
Vestibular System
CN VIII - Vestibulocochlear nerve
- Nuclei is in (medulla/pons)
- Cochlear nucleus in pontine surface
- Cochlear branch - (hearing/balance)
- Vestibular branch - (hearing/balance)
pons; hearing; balance
Vestibular Cochlear System: hearing and balance
Vestibular Labyrinth
-Works to see how we move in space, detect movement, and detect where we are in space
Coo
Vestibular cochlear structures
- 2 receptor organs
- Semicircular canal and otolith organs
- 2 semicircular canals - organized within 90 degrees of each other
- Horizontal
- Anterior
- Posterior
- Detects
- (Non-rotational/Rotational) head movements
- (Static/Angular) acceleration
- Bony labyrinth protects the structure
- Fluid aka endolymph sits between the membrane and bone - potassium is added into the cell which is important for action potential generation
- Fluid Endolymph – critical for function of vestibular organ
Rotational; Angular
Spatial Alignment of Sensory Receptors
- Essential for coordination of (static movement/rotation) - organization within 90 degrees of each other
- Orientation helps us pick up specific differences
rotation
Receptors
- Ampulla
- (Minimization/Enlargement) at the end of each sensory canal that contains sensory receptors
- Contains ____ ampullaris
Enlargement; crista
Crista Ampullaris & Cupula
- Canal is filled with endolymph
- Cupula: gelatinous structure that contains type 1 and type 2 hair cells
- Cupula is essential for (exciting/dampening) signals coming in
dampening
Hair Cells
- 60-100 (stereocilia/kinocilium) and 1 (stereocilia/kinocilium) per hair cell
- Hair cells are located within the (capitulum/cupula)
- Supporting cell matrix of the _____ are where the hair cells are embedded
- Stereocilia: (short/long)
- Kinocilium: (short/long)
- Stereocilia and kinocilia are connected bc the way the stereocilia move (either towards or away from the kinocilia) is essentially how the vestibular system works
stereocilia; kinocilia cupula; cupula; short; long
Hair Cell Transduction
-Movement of the hair cells = signaling to the brain that movement is (not occurring/occurring)
occurring
Crista Ampullaris & Cupula
- Endolymph moves, pushing on the cupula, resulting in hair cell mvmt. Singal from hair cells results in brain detecting mvmt
- Crista that hair cell is embedded, springs the hair cells back upright once movement stops
Got it
Directional Sensitivity
At rest, left and right (engage each other/cancel out)
Turn left, left receptor (depolarizes/hyperpolarizes), right (depolarizes/hyperpolarizes). Difference alerts to head turn direction
cancel out; depolarizes; hyperpolarizes
Structures
2 receptor organs - semicircular canal & otolith organs
2 otolith organs - _____ & _____
Utricle & Saccule
Receptors
Receptors
- 2 otolith organs
- Utricle and saccule
- Orientation of head with respect to gravity
- Translational head movements and head tilt
- Linear acceleration
- Head tilt
- Utricles → (Vertical: cervical flexion and extension/Horizontal: left to right)
- Saccule → (Vertical: cervical flexion and extension/Horizontal: left to right)
Horizontal: left to right; Vertical: cervical flexion and extension
Otolith Organs: Otolithic Membrane and Otoconia
_____ - crystal like substance that sits on top of the gel
Octonia
Otolith Organs
Head tilt: forward, backward, side to side
Head translation: head bob up and down (gravity)
head translate fwd or bkwd (walking)
Lol okay?
Hair Cell Orientation
Okay
Directional Sensitivity
(Saccule/Utricles): horizontal tilt (tilt left to right)
(Saccule/Utricles) : vertical tilt (nod yes/no)
Flexion and extension - (saccule/utricles)
Take home: Otoconia moves gel (right/left).
One side of striola depolarizes/other side hyper polarizes.
Utricles; Saccule; saccule left;
Spatial Alignment of Sensory Receptors
- The organ is angled _ degrees (upward/downward) so when one looks down when walking, everything lines up perfectly to detect motion occurring
- If one does not look down while walking, they must have the proprioceptors and kinoreceptors to detect movement
All receptors are aligned (parallel/perpendicular) to each other.
Vestibular organ is angled _ degrees off of the horizontal
30; upward; 30
Head angles
Got it
Vestibular Information Systems
- Vestibulo Thalamic: input to ipsilateral thalamus - (head and neck control/head with visual and audio)
- Vestibulo-cerebellar tract: coordinates (head and neck control/head with visual and audio)
- Input from vestibular, superior (visual) and inferior colliculi (auditory)
- Vestibulospinal tract: descending CL neck muscle modulation
- (Lateral/Medial) longitudinal fasciculus
head and neck control; head with visual and audio; Medial`
Medial Longitudinal Fasciculus
- Connects CN VIII to III, IV, VI
- Connects vestibulocochlear nerve to oculomotor, trochlear and abducens
- Connects vestibular organ to extraocular muscles to coordinate eye movement in respect to head movement
- Ascending and descending tracts
- Info to and from
- FEST - _____, _____, _____. ____
Four
Eight
Six
Three
Commissural Fibers
- (Comparator/Compensation) function- Associated with head rotations and translation
- (Comparator/Compensation) function - Restoration of impaired reflexes and postural control in cases of unilateral receptors damage
- Central adjustment of vestibular neurons
Comparator; Compensation
Vestibulo Ocular Reflex (VOR)
- keep gaze fixed on object while head is (still/moving)
- Gaze stabilization
- Ex look straight while turning head to left
- Right eye – (adduction/abduction)
- Left eye – (adduction/abduction)
- Right eye - excite (abducens/oculomotor), inhibit (abducens/oculomotor)
- Left eye- excite (abducens/oculomotor), inhibit (abducens/oculomotor)
- Head can move - up, down, left, right, diagonal
moving; abduction; adduction; abducens; oculomotor; oculomotor; abducens
Vestibulospinal & Vestibulocollic Reflexes
- Vestibulospinal
- Side to which the head is inclined
- Paravertebral and proximal limb extensor muscles (excited/inhibited) on the side you are tilting towards
- Opposite side to which the head is inclined
- Paraveretebral and proximal limb extensor muscles (excited/inhibited)
- Preserves upright posture and balance
- Vestibulocollic
- Excitatory and inhibitory stimuli to neck extensor and flexor muscles
- Falling forward
- Neck extensors are (inhibited/stimulated)
- Neck flexors (inhibited/stimulated)
- Falling backward
- Neck flexors are (stimulated/inhibited)
- Neck extensors are (stimulated/inhibited)
excited; inhibited; stimulated; inhibited; stimulated; inhibited
Clinical Correlation CN VIIIHair Cell Transduction Impairments
- Antibiotic ototoxic effects
- Aging
- Hair cell degeneration
- More degeneration of type (1/2) hair cells
2;
Clinical Correlation CN VIII
- Benign paroxysmal positional vertigo (BPPV)
- Otoconial crystals separate from otolith membrane
- Typically from (sacuule/utricle)
- Lodge in cupula of semicircular canal
- Often the (anterior/posterior) canal
- Abnormal excessive cupula deflection
- Brief periods of vertigo that coincide with head mvmts
utricle; posterior
