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Sensory Neuroscience 316 > Lecture 20: Balance One > Flashcards

Lecture 20: Balance One Flashcards

1
Q

Where is the first synapse of the auditory nerve?

A
  • Cochlear nucleus. (all afferent fibres terminate here, nothing further)
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2
Q

Describe the cochlear nucleus first synapse;

A
  • Obligatory synapse of all afferent auditory nerve fibres
  • Some neural features to extra features of sound (e.g onset, offset, noise vs tones)
  • Somatosensory influence. (tonotopic organisation) Important for cleaning the response and removing any biological noise i.e Heart and resp noise
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3
Q

How can the cochlear nucleus be divided?

A

In three;

  • Dorsal cochlear nucleus
  • Posteroventral cochlear nucleus
  • Anteroventral cochlear nucleus
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4
Q

How do the cell types in the cochlear nucleus differ?

A

DCN; Fusiform cell types

PCN and ACN = bushy and stellate cell types

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5
Q

Whats the function of the DCN:

A
  • Projects to midbrain

- More complex sound processing possibly important for speech detection

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6
Q

Whats the function of the vestibular system?

A

Balance and posture

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7
Q

What is balance?

A
  • Maintenance of steady position

Essential for;

  • coordination of motor responses, eye movement, posture
  • Dynamic and static equilibrium
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8
Q

What is a key feature of balance?

A

Highly integrated system

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9
Q

what is integrated in balance?

A

Involves integration of;

  • Vision
  • Vestibular organs
  • Proprioceptive inputs
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10
Q

What pathways are involved in balance?

A

Sensory input;

  • Vision
  • Vestibular organs
  • Proprioceptive inputs

Integration of input;

  • Cerebellum (posture,movement,balance co-ordination)
  • Cerebral cortex (memory, higher think int)
  • Brain stem (sensory int)

Motor Output:

  • Vestibulo-occular reflex
  • Motor impulses (to control eye movement)
  • Motor impulses (to control posture)
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11
Q

What is the role of cognition in balance?

A
  • Self motion perception
  • Bodily self consciousness
  • Spatial navigation
  • Spatial learning
  • Spatial memory and object recognition
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12
Q

Describe hippocampal connections, spatial memory and vestibular system interplay

A
  • Hippocampal atrophy with bilateral vestibular lesion (i.e vestibular system contributes to spatial memory)
  • Spatial representation in hippocampus influenced by vestibular organ
  • contribute to navigational deficits in people with abnormal vestibular function
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13
Q

What does the vestibular system sense?

A
  • Sense dynamic and static position of the head.
  • Detect linear and angular acceleration of the head.
  • Conscious awareness of head position and reflex control of eye movements.
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14
Q

Describe the sensitivity of the vestibular system;

A

Vestibular system is exquisitely sensitive and finely balanced

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15
Q

Describe the impact of small derangement of the vestibular system:

A

Minor, acute derangement have catastrophic effects on balance causing VERTIGO (sense of losing balance, movement), disorientation and nausea

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16
Q

What may chronic or gradual loss of vestibular function lead to?

A

Chronic or gradual loss of vestibular function may have limited symptom with compensation at central nuclei

17
Q

What is vertigo?

A

Perception of motion, person or environment (the room is spinning) where there is none

  • Differes from light headedness or dizziness
  • accompanied by visceral, autonomic symptoms e.g pallor, sweating, nausea, vomiting
18
Q

What is motion sickness?

A

Conflict between vestibular ,visual, proprioceptive inputs with an expected internal mode.

Mismatch of inputs promotes the symptoms associated with vertigo and motion sickness

19
Q

Whats the effect of microgravity on vestibular function?

A
  • No/low gravity renders the vestibular system useless, thus leading to motion sickness
  • Cant sense direction
20
Q

What nerve projects from the vestibular system?

A

Sensory organs in the inner ear project via vestibular section of 8th cranial nerve to vestibular nuclei in brain stem

21
Q

What are the outputs of the vestibular nuclei?

A
  • Motor spinal cord
  • Cerebellum
  • ANS
  • Cerebral cortex
  • Nuclei 3,4,6 (that drive eye muscles, so cranial nerves)
22
Q

What are the directions of movement of the head?

A

Translational (linear) = XYZ

Rotational (angular) = Yaw, Pitch, Roll

23
Q

What structures from the vestibular system?

A

3 semicircular canals;

  • Superior (Anterior)
  • Posterior
  • Lateral (horizontal)

Saccule
Utricle

24
Q

What is a feature of all three semicircular canals?

A
  • Ampullae of semicircular canals

- Contain cristae of ampullaris; detects angular acceleration (sensory cells)

25
Q

What do the utricle and saccule contain?

A

Contain otolithic organs, the macula sacculis and utriculus that detect static head position and linear acceleration

26
Q

Describe the anatomical route of the vestibular nerves;

A

Superior and inferior vestibular nerve with cell bodies in scarpas ganglion exits as part of vestibulocochlear nerve in internal auditory meatus

27
Q

What does the superior portion of the vestibular nerve innervate?

A
  • Utricle, anterior port of saccule, anterior and lateral semicircular canals
28
Q

What does the inferior portion of the vestibular nerve innervate?

A

Posterior part of saccule and posterior semicircular canal

29
Q

Whats an important feature of the canals?

A

Vestibular sensory organs operate bilaterally as pairs

VIP

30
Q

How are the lateral canals paired?

A

The L and R canals are paired

31
Q

How are the A and P canals paired?

A

The Anterior canal is paired with the posterior canal of the other ear.

32
Q

Describe the sensory cells in the vestibular organs;

A

Similar to sensory cells in the cochlea, except there is LARGE kinocilium (polarises the cells)

Type One and Type Two, huge synapses

33
Q

Describe the sensory cells in the vestibular organ;

A

Invaginates to form a dam in the tube, gelatinous structure sits atop of sensory cells, (Cupula) (same density)

34
Q

Describe kinocelium placement on sensory cells;

A

Kinocelium sits same side across all sensory cells. (therefore depending on direction of movement = inhib or activate)

Sensory Neuroscience 316 (32 decks)

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