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34 Cards in this Set
- Front
- Back
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What are conjugate eye movements?
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Eyes move together, visual axes displaced in the same direction
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How are eye movements measured?
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Electro-oculography
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What is the action of this muscle:
medial rectus |
adduction
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What is the action of this muscle:
lateral rectus |
abduction
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What is the action of this muscle:
superior rectus |
elevation
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What is the action of this muscle:
inferior rectus |
depression
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What is the action of this muscle:
superior oblique |
depression, intorsion, abducts
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What is the action of this muscle:
inferior oblique |
elevation, extorsion, abduction
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Which two extraocular muscles have cell bodies in a contralateral nucleus?
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Superior Oblique
Superior Rectus |
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How are conjugate movements coordinated?
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Via the medial longitudinal fasciculus (MLF)
Internuclear neurons in an ipsilateral nucleus project to a contralateral nucleus via MLF for coexcitation, and to ipsilateral target nucleus for inhibition (prevents nystagmus) E.g. left abducens nucleus (VI) projects to right oculomotor nucleus (III) for conjugate left gaze and inhibits left III nucleus (prevent nystagmus) |
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What occurs when the MLF is interrupted?
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Internuclear opthalmoplegia (INO), aka. MLF Syndrome
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What are the signs of right ipsilateral internuclear opthalmoplegia (INO)?
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Inability to adduct the right eye during left lateral gaze
Nystagmus of left abducting eye |
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Where are vergeance movements organized?
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Rostral midbrain (no MLF used)
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What is the "One and a Half Syndrome"?
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Large lesion involving CN VI will produce an ipsilateral CN VI palsy and knock out both MLF projections. Only contralateral VII nerve intact
Called one & half b/c only half of right eye movement intact |
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Where are saccadic eye movements generated?
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Superior colliculus
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Where are slow movements generated?
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Cerebellum
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What is the visual grasp reflex?
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Quick saccadic movement to bring novel stimulus into foveal view
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Describe quick movements
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Always conjugate
Sacccadic Displace image across the retina |
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Describe slow movements
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Smooth pursuit
Targeted Stabilize the image on the retina Vergence movements are usually slow, but may be assisted by quick conjugate movements |
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What is retinal slip?
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Slippage of an image across the retina. First stage of smooth pursuit
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Lesions in the midbrain evoke what deficits?
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Disrupt vertical eye movements
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What is Parinaud's syndrome?
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Occurs when a pinealoma compresses the midbrain
Paralyzes vertical gaze *also called syndrom of the cerebral aqueduct |
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What brain areas are involved in voluntary oculomotor control?
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Primary visual cortex (occipital lobe)
Frontal eye fields (frontal lobe) Posterior parietal cortex *Temporal lobe may contribute to initiation of eye movement |
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Sudden damage to cerebral hemispheres (e.g. stroke) causes what clinical sign and why?
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Tonic deviation TOWARD the lesion because the intact hemisphere operates unopposed, pushing the eyes to the opposite (lesioned) side
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What effect does epilepsy have on the eyes?
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During a seizure, eyes will look AWAY from the lesion - eyes are driven to the normal, non-seizing hemisphere
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The visual grasp reflex is mediated by what area of the brain?
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Superior colliculus
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What brain areas are important for smooth pursuit?
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Cortex --> Pontine nuclei --> Cerebellum (flocculonodular lobes)
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What does the flocculonodular lobe mediate?
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smooth, conjugate movements
neurons carry information about gaze velocity |
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What is the significance of the paramedian pontine reticular formation?
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Generates excitatory input for horizontal saccadic movement - receives input from superior colliculus
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Bethanecol (Urecholine)
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Muscarinic autonomic agonist - increases bladder emptying
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Oxybutinin (Ditropan)
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Muscarinic autonomic antagonist - decreases bladder emptying, increases urine retention
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Which neurotransmitter systems operate via the phosphatidylinositol system?
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Serotonin
Acetylcholine |
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Atropine
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Muscarinic antagonist
Increases heart rate, slows GI motility, dilates pupils |
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Scopolamine
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Muscarinic antagonist
Causes memory disturbance |
