Visual pathways PP

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Visual Pathways
Eye
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Lens
Cornea
Iris
Suspensory ligaments
Ciliary body
Ciliary muscle
Retina
Choroid
Sclera
Subarachnoid space
Central retinal artery and vein
Optic nerve
Vitreous body
Conjunctiva
Retina - contains
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Pigment epithelial cells- absorb light
that passes through the retina
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First neuron
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Rods- vision in light of low
intensity
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Cones- visual acuity and color
vision
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Second neuron
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Bipolar- second neurons of visual
pathway
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Ganglion
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Ganglion- third neurons of visual
pathway
Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD
Additional areas:
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Optic disc- Area optic nerve exits retina
(blind spot- no receptors)
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Macula lutea- central region of the
retina
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Fovea centralis- area of the central part
of the retina that is indented and
contains mainly cones for visual acuity
Visual Pathway•
Light travels through retina from internal
to external exciting the rods and cones
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Impulse is transferred from rods and
cones to bipolar cells
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Bipolar cells synapse on the dendrites of
the ganglion cells
Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD
Visual Pathway•
Ganglion cells form the optic nerve at
the level of the optic disc
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Optic nerves combine to form optic
chiasm
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Enters lateral geniculate body to synapse
Visual Pathway- forth order neurons
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Cell body located in the lateral
geniculate body
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Axon travels posteriorly (optic
radiations)
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Terminates in the visual cortex in the
occipital lobe
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1. Right eye blindness - trauma, optic neuritis
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2. Bitemporal hemianopsia - pituitary tumors
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3. Right nasal hemianopsia - pressure by aneurysm of internal carotid artery
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4. Left homonymous hemianopsia - abscess or tumor of temporal lobe
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5. Left homonymous hemianopsia - anterior choroidal artery dysfunction
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6. Left homonymous superior quadratic anopsia - temporal or occipital lobe
dysfunction
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7. Left homonymous inferior quadratic anopsia - parietal or occipital lobe tumor
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8. Left homonymous hemianopsia with macular preservation - posterior cerebral artery
dysfunctions, tumors, trauma
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Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD
Lecture 14 - Visual
Visual Reflexes
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Light reflex (constriction- parasympathetic): when light enters the pupil the pupil constricts
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Neuronal elements of the retina
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Optic nerve
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Optic chiasm
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Optic tract
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Enter the brachium of the superior colliculus (superior brachium)
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Pretectal region
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Oculomotor nuclear complex (Edinger-Westphal nucleus)
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Preganglionic parasympathetic axons to the ciliary ganglion behind eye
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Short ciliary nerves
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Terminate on the constrictor muscle of the iris
Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD
Lecture 14 - Visual
Visual Reflexes
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Light reflex (dilation- sympathetic): when the pupil widens. Occurs passively when parasympathetic
tone decreases and actively when sympathetic tone increases
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Hypothalamus
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Spinal cord (T1)
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Ventral root
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White communicating rami
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Ascend sympathetic trunk
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Synapse in superior cervical ganglion with post-synaptic sympathetic ganglion
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Travel in the carotid plexus
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Terminate on the dilator muscle of the iris
Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD
Visual Reflexes
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Accommodation reflex: Process in which a clear visual image is maintained as gaze is shifted from a
distant to a near point
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3 components
• Convergence of the eyes
• Pupillary constriction
• Thickening of the lens
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Initiated by occipital cortex
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Impulses go to:
• Edinger-Westphal nucleus for changes in the lens and pupil (parasympathetic)
• Somatic nuclei: for convergence of the eyes (medial rectus
Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

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