Ch. 16: Vestibular and Visual System Flashcards

1
Q

How many semicircular canals are there in the inner ear? What angles do they face?

A
  • 3 per side of the body
    • Anterior: 45º forward
    • Posterior: 45º deg backward
    • Horizontal: tilted 30º off horizontal
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2
Q

What is the function of the semicircular canals?

A

Keeps eyes focused on the world around you

(All 3 together can detect any direction your head moves)

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3
Q

What is the purpose of the hair cells in the inner ear and where are they located?

A
  • Provide Baseline activity and when moving
  • Located at one end of each semi circle in fluid
    • bend of hair cells → creates AP’s
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4
Q

What is “paired activity” of the semicirular canals?

A

AP’s inc on side toward rotation and dec proportionally on side away from rotation.

(Anterior semicircle or right is in line with posterior semicircle on left)

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5
Q

Why are the semicircular canals important?

A

stabilize VISION when HEAD is moving

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6
Q

What is inside the Otolithic Organs?

A

Have hair cells that are anchored in jelly with rocks on top.

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7
Q

How do the Otolithic Organs generate AP’s?

A
  • Respond to pull of gravity (helps w/postural stabilty - connected to vestibulospinal tract (keep you upright).
  • Gravity pulls hair cells → they bend → generate AP’s
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8
Q

How many Otolithic Organs do you have?

A

2 per side

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9
Q

Otolithic Organs respond to what type of movement?

A
  • Linear acceleration/deceleration
  • Chang in pull of gravity
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10
Q

What are the inputs to the vestibular nuclei (CN VIII)?

A
  • Vestibular Information - head movement & pull of gravity
  • Visual Information - light information - can see relative position
  • Unconscious proprioceptive info - position of body and joints in space
  • Tactile Info - pressure sensors in skin
  • Auditory info - change of sound detects movement
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11
Q

What are the outputs from the vestibular nuclei (CN VIII)?

A
  • Cerebral Cortex - “I’m dizzy”
  • Med Longitudinal Fasciculus/Extraocular (CN II, IV, VI) nuclei - eyes controlled relative to head movement
  • Superior Colliculus/Accessory N - contract muscles to keep you up right
  • Med vestibulospinal tract - posture of head & upper body - maintain equillibrium
  • Lat vestibulospinal tract - posture of trunk & lower body - maintain equillibrium
  • Reticular Formation - affect consciousness = nausea & vomitting
  • Cerebellum - Can influence posture & eye movements
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12
Q

What are the Nasal Retina?

A
  • Half of retina closest to nose
  • “temporal” visual field
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13
Q

What are the Temporal Retina?

A
  • Closest to temple
  • “Nasal” visual field
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14
Q

What light info does the Optic Nerve Receive?

A

info from ALL visual space

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15
Q

What light info does the Optic Tract Receive?

A

Only one field of vision

(ex: pulls right visual field from both eyes to left side of brain through chiasm)

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16
Q

What is the purpose of the Optic Chiasm?

A

Allows nasal retina information to switch sides of the brain so all info in optic tract reflects one visual field

17
Q

What is the Action Stream (dorsal)?

A
  • From occipital to motor planning cortex
    • Motor plan to get what you see
    • characterize things by colors, shapes, contours
18
Q

What is the Preception Stream (ventral)?

A
  • Occipital cortex to temporal lobe
    • Recognize & name what you see
19
Q

Visual information diverges in the optic tract and goes to what 3 routes?

A
  • Conscious sight: Thalamus → Occipital Cortex
    • Action stream (dorsal)
    • Perception stream (ventral)
  • Orientation & visually guided eye movments: Superior Colliculus
    • Reflex movement of head and eyes when something thrown at you
  • Midbrain connection of pupillary reflexes: Pretectal Area
    • Adjust pupils & curvature of eye
20
Q

What is Gaze Stabilization?

A

Keep eyes focused on object when head is moving

21
Q

What is Direction of Gaze?

A

Move eyes to focus on an object of interest

22
Q

What is Conjugate movement?

A

Both eyes moving in the same direction (ex: tracking side to side)

23
Q

What is Disconjugate movement?

A

Eyes moving in different directions (ex: cross eyes)

24
Q

What 2 reflexes help with Gaze Stabilization?

A
  • Vestibulo-Ocular Reflex (VOR) - fast head movements
    • Eyes stay steady while head moves
  • Optokinetic Reflex - Slow head movements
    • Eyes stay focused on object when head moving slow
25
Q

What 4 things help with Direction of Gaze?

A
  • Smoot Pursuit: consciouly contract muscles to move the eyes while head is still
  • Saccades: Jumps in eye movement. Normal when scanning
    • Voluntary: look from one person to another
    • Reflexive: Catch something in periphery and look to see what it is
  • Vergence: Looking cross eyed (very near objects)
  • VOR suppression/cancellation:consciously move eyes WITH head - conscious override of VOR
26
Q

What is Nystagmus?

A
  • Involuntary back and forth movements of eye → keep world steady when moving (ex: spinning really fast)
27
Q

When is Nystagmus Physiologic?

A
  • During acceleration/deceleration of head (ex: spinning)
    • Combo of
      • VOR (slow - eyes lag behind)
      • Saccade (fast - eys catch up)
28
Q

When is Nystagmus Pathologic?

A

When there is no appropriate stimulus (ex: simply laying down)

29
Q
A