CN II-Optic Nerve and Visual System Flashcards Preview

DPT 736 Neuroanatomy > CN II-Optic Nerve and Visual System > Flashcards

Flashcards in CN II-Optic Nerve and Visual System Deck (13)
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1
Q

Visual System

A
  • most highly developed of sensory modalities
  • optic nerve and retina grow out of diencephalon
  • retina encodes visual information and projects that info to brain via myelinated fibers in optic nerve
  • optic nerve fibers undergo hemidecussation (part of fibers cross) in optic chiasm and project to primary visual cortex of the occipital lobe via thalamus (lat geniculate body)
  • from eye –> optic chiasm = optic nerve
  • optic chiasm to lateral geniculate body = optic tract
  • lat geniculate body –> 1* visual cortex = optic radiation
2
Q

The Eye

A
  • optic nerve (II) emerges from posterior pole
  • sclera: white, fibrous, protective outer layer of eye; over the anterior pole it is transparent and called cornea-light passes through to lens and then retina
  • iris: fibers arranged in circular and radial fashion (under control of autonomic nervous system): circular (pupil constriction)-parasympathetic; radial (dilate pupil): sympathetic
  • pupil: central aperture
  • transition from eye into optic thalamus nerve = optic disc/blind spot
  • ciliary body: contains ciliary muscle (parasympathetic innervation), alters shape of lens
  • choroid: dark pigmented inner surface of sclera that absorbs light and reduces reflection
  • retina: inner surface of choroid, photoreceptive
3
Q

Diabetic Retinopathy

A
  • eye filled with vitreous fluid

- diabetics who aren’t under good control –> leaky vessels in eye –> min bleeds –> see floaters in vision

4
Q

Retina

A
  • photoreceptors: transduce light to electrical impulses by a series of photochemical reactions and physicochemical changes
  • two varieties: rods-20x more numerous, very sensitive to light; cones-responsible for color
  • highest acuity and high spatial and temporal resolution in cones
  • more cones at fovea
  • photoreceptor (rods and cones) –> bipolar cells –> optic nerve
5
Q

Visual Field

A
  • visual field consists of four quadrants
  • image formed is inverted both vertically and laterally
  • objects that lie in left half of visual field form an image on the right half of right eye and the right half of the left eye
6
Q

Visual Pathways

A
  • retinal ganglion axon travel in optic nerve and converge in optic chiasma
  • axons from medial portions of retina decussate at chiasma and pass into contralateral optic tract
  • axons from lateral portions of retina remain ipsilateral through chiasma
  • axons then travel to thalamus, a relatively small number of axons bypass thalamus and go to pretectal region and superior colliculi for mediation of pupillary light reflex
7
Q

Thalamocortical Neurons (3rd Order)

A

-project to primary visual cortex of occipital lobe: primarily on medial aspect of the occipital lobe above and below calcarine sulcus

8
Q

Visual Association Cortex

A
  • surrounding primary visual cortex
  • interpretation of visual images
  • recognition
  • depth perception
  • color vision
9
Q

Visual Field Disorders

A
  • monocular blindness: cataract, intraocular hemorrhage, retinal detachment
  • bitemporal hemianopia: compression of optic chiasma by pituitary tumor
  • homonymous hemianopia: vascular or neoplastic lesions of the optic tract, optic radiation
10
Q

Meyer’s Loop

A
  • medial is parietal lobe goes to upper bank of calcarine fissure and receives images from lower visual field
  • temporal is meyer’s loop white matter tracts that go to lower bank of calcarine fissure and receives vision from upper visual quadrant from opposite eye
  • look at drown out schematics
11
Q

Optic Chiasm Pressure

A
  • pituitary gland lies under optic chiasm –> tumor here would put pressure on optic chiasm at central fibers = tunnel vision
  • bitemporal hemianopia
12
Q

L Optic Nerve Disruption

A
  • monocular anopia

- blindness in left eye

13
Q

Lesion on L optic Tract

A
  • affects right side of both eyes

- right homonymous heminaopia