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RHSC 420 Final Exam Lectures 6 – 9 | Questions And Answers Latest {} A+ Graded | 100% Verified
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RHSC 420 Final Exam Lectures 6 – 9 | Questions And Answers Latest {} A+ Graded | 100% Verified
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RHSC 420 Final Exam Lectures 6 – 9 | Questions And Answers Latest {2024- 2025} A+Graded | 100% Verified
What are the main functions of the vestibular system? - - provide us with our sense of balance and head
position
What are the peripheral vestibular organs? - - semicircular canals
- otolith organs
What is the function of the semicircular canals? - - respond to head movement (turning) by detecting
angular acceleration
Describe the structure of the semicircular ducts. - - each has swelling on end (ampulla)
- inside ampulla is a gelatinous mass (cupula)
- cupula sits on top of hair cells
- kinocilium and stereocilia protrude out of hair cells in cupula
Name the three perpendicular semicircular ducts. - 1) superior
2) lateral
3) posterior
Describe how kinocilium and stereocilia work together to general a membrane potential. - - get bend by
movement of cupula during angular acceleration
- bending causes change in membrane potential of hair cells, which synapse on primary vestibular
neurons
- mechanosensitive ion channels in stereocilia (movement of stereocilia cause change in Vm)
Describe the movement of stereocilia in relation to the kinocilum to result in depolarization or
hyperpolarization. - 1) depolarization - stereocilia move towards kinocilium
2) hyperpolarization - stereocilia move away from kinocilium
,3) resting - no movement of stereocilia
What are the two otolith organs? - 1) utricle - horizontal with respect to head
2) saccule - vertical with respect to head
What are the main functions of the otolith organs? - - respond to head position and linear acceleration
Describe the otolith organs. - - contain hair cells
- otolithic membrane (contains CaCO3) sits on top of hair cells
- suspended in macula
Describe how head position information is transmitted. - - when head position changes, membrane
bends top of the hair cells
- same as in cupula with kinocilium and stereocilia
Describe the central connections of the vestibular system. - primary vestibular neurons (bipolar
neurons) have dendrites innervating hair cells, CB in vestibular ganglion axon going to CNS (form
vestibular nerve)
- vestibular nerve joins to cochlear division => vestibulocochlear nerve
- vestibulocochlear nerve enters brainstem at pontomedullary sulcus; synapse in vestibular nuclear
complex
- some axons bypass vestibular nuclear complex and go straight to CE via inferior cerebellar peduncles
What are the nuclei of the vestibular nuclear complex (VNC)? - 1) interior vestibular nucleus
2) lateral vestibular nucleus
3) superior vestibular nucleus
4) medial vestibular nucleus
What are the inputs to the VNC? - 1) primary vestibular neurons
2) projections from flocculonodular lobe of cerebellum
,3) projections from spinal cord carrying info about posture and body orientation; these arrive directly as
spinovestibular fibres traveling with posterior spinocerebellar tract, or indirectly via CE or RF
4) projections from contralateral vestibular nuclei
Where do the outputs from the VPN? - - Cerebellum
- spinal cord (lateral/medial vestibulospinal)
- thalamus and then to parietal lobe of cortex, leading to conscious awareness of equilibrium and spatial
orientation
- cranial motor nuclei of extraocular muscles (CN III, IV, VI) via MLF
- RF including centre controlling vomiting
- contralateral vestibular nuclei
What is the function of the lateral vestibulospinal tract and how does it project on the spinal cord? - -
projects to all levels of ipsilateral spinal cord
- leads to postural changes in response to body tilt
What is the function of the medial vestibulospinal tract and how does it project on the spinal cord? - -
projects bilaterally to cervical spinal cord
- responsible for postural changes of neck muscles
What is the vestibuloocular reflex (VOR)? - - results in the gaze staying fixed on an object, even when the
head moves; works in complete dark
- important for stabilizing vision
How does VOR work? - - semi-circular canals signal how fast head is rotating
- oculomotor system responds by rotating eyes at equal and opposite velocity
- visual images kept fixed on retina
What connects does the VOR depend on? - - connections between VNC and nuclei of extraoculary
muscles via MLF
, What is nystagmus? - - rhythmic oscillatory eye movements
- normally seen when a person is under sustained rotation
- eyes driven to edge of orbit (slow phase), and then reverse direction rapidly (quick phase)
How is nystagmus named? - - named for direction of rapid movement
- i.e. if eyes move slowly to left and quickly back to right, RIGHT nystagmus
How can nystagmus arise? - - can occur pathologically after vestibular lesions
- quick phase away from side of lesion
How can damage to the vestibular system occur? - 1) inner ear infection
2) toxic reaction to certain antibiotics (e.g. streptomycin, gentamycin)
3) traumatic head injury
4) stroke
5) Meniere's disease, which is caused by excess endolymph
What are some symptoms of vestibular damage? - 1) balance deficits/vertigo
2) impaired gaze stabilization
3) spontaneous nystagmus (pathological)
4) involuntary rhythmic movements of one or both eyes (horizontal, vertical, or rotary) at rest
What are the main functions of the cerebellum? - - integrating sensory and motor information
What does the cerebellum influence? - - muscle tone
- postural reflexes
- balance and equilibrium
- coordination
- fine motor control
- motor learning
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