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30 Cards in this Set
- Front
- Back
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The visual system provides...
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Eye movement control, sight, information used in postural and limb movement control
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Oculomotor system provides...
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Extraocular muscle control eye movements = 6 muscles.
Enable us to coordinate head and eye movements. |
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Name 3 pairs of Extraocular Muslces.
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1. Medial & Lateral rectus = Adduction and abduction
2. Superior & Inferior rectus = Elevation & depression 3. Superior & Inferior Oblique = When eye adducted, up & in, With abduction, rotate eye. |
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Wnat cranial nerves innervate extraocular muscles?
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CN 3 - Oculomotor for nucleus in midbrain, and superior, medial & inferior rectus. Inferior oblique.
CN 4 - Trochlear for Neucleus in midbrain, and superior oblique. CN 6 - Abducens for neuleus between pons & medulla, and lateral rectus. |
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What system works together with visual system?
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Vestibular system to keep eyes stable during head movement and direct gaze at visual target.
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Name 4 types of eye movements and describe each.
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1. Fast saccadic - Fast eye movement for searching, especially in the periphery (Conjugate).
2. Smooth pursuits - Occurs while following a moving target (Conjugate). 3. Vergence - Maintains fixation of a target from far visual field to near (or vice versa). 4. VOR (vestibulo-ocular reflex) - Stabilizes visual images during head movements. |
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What is Retina?
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Retina is part of the CNS.
Converts light into electrical signals. Nasal hemiretina & temporal hemiretina. |
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What is Macula?
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Concave area.
Highest concentration of cones. |
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What is Fovea?
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Center part of concave area.
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What is Photoreceptors?
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Have rods that detect dim light and cones that detect color & visual acuity.
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What is visual field?
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The amount of the world you can see at any one time without head or eye movement.
Inverted representation. |
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What is nasal retina?
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1/2 of retina that processes visual information nearest the nose.
Crosses midline in optic chasm and projects to contralateral visual cortex. |
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What is temporal retina?
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1/2 of retina that processes visual information nearest the temporal bone.
Continue ipsilaterally throught the optic chiasm and project to ipsilateral cortex. |
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What is monocular zone?
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Visual field that is seen by one eye only.
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What is binocular zone?
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Visual field that is seen by both eyes.
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What is the optic nerve?
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Bundle of axons passing from retina and optic chiasm.
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What is optic chiasm?
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Formed by optic nerves of both eyes.
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What is optic tract?
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Conveys visual info from chiasm to LGN.
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What is subcortical projections?
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Superior colliculi and lateral geniculate nucleus (LGN).
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What is optic radiation?
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Emerge from LGN and project to primary visual cortex.
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What makes up the visual cortex?
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Primary visual cortex (V1) and visual association cortex.
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What is the primary visual cortex (V1)?
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Discrimates shapes, size, texture of objects.
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What is the visual association cortex?
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Analyzes for color and motion.
Flows to other areas of cerebral cortex to adjust movements or to visually identify objects. |
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What is Macular Degeneration?
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Retinal disorder.
Loss of vision in the center of the visual field (macula). Peripherial vision remains. Make it difficult or impossible to read or recognize faces. More prevelent in males than females. |
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Name two types of macular degeneration.
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Dry macular degeneration: The cells of the macula slowly begin to break down. 90% of cases.
Wet macular degeneration: Abnormal blood vessels grow behind the macula then bleed. 10% of cases. |
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What is Lesion?
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Damaged tissue.
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Lesion to optic nerve?
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Total loss of vision in ipsilateral eye = blindness in one eye.
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Lesion to optic chiasm?
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Bitemporal hemianopsia = Loss of Rt. & Lt. monocular zone.
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Lesion to to optic tract, optic radiation, LGN?
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Contralateral homonymous hemianopsia = Loss of entire contralateral visual field.
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Lesion to visual cortex?
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Contralateral homonymous hemianopsia. Possibly with macular sparing (retain central vision) = If LGN, optic tract & optic radiation is not damaged.
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