Transcript Sensory Physiology

Vision
Anatomy of the Eye
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Fibrous tunic
– Sclera
– Cornea
Anatomy of the Eye
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Vascular tunic = Uvea
– Choroid
– Ciliary body
– Iris
– Pupil
Anatomy of the Eye
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Nervous tunic = Retina & optic nerve
– Outer pigmented layer
– Nervous layer
Photoreceptors
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Rods
 Cones
 Macula
 Fovea centralis
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Optic Nerve
 Optic disc
 Blind Spot
Anatomy of the Eye –
Miscellaneous structures
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Lens
 Anterior cavity
– Aqueous humor
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Posterior cavity
– Vitreous humor
Anatomy – Accessory
structures
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Eyelids = Palpebrae
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Tarsal plate
Meibomian glands
Palpebral fissure
Lateral commissure
Medial commissure
Caruncle
Sebaceous ciliary glands
Anatomy – Accessory
structures
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Conjunctiva
– Palpebral
– Bulbar
Anatomy – Accessory
structures
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Lacrimal apparatus
– Function
– Lacrimal gland
– Lacrimal puncta
– Lacrimal canal
– Nasolacrimal duct
Vision
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Light
 Refraction
 Emmetropia = Normal vision, light rays
focus on a single point called the Focal
Point
Focal Point
Retina
Vision
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Accommodation
– For close vision
– Pupils constrict
– Eyeballs converge
– Near point of vision
Vision
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Eye movement controls
 Voluntary fixation (premotor area)
 Involuntary fixation (visual area)
Vision
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Binocular vision
 Diplopia
 Strabismus
Photoreceptors of Vision
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Rods
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Rhodopsin is photopigment
Numerous – about 120 million
Sensitive to light
Relative lack of color discrimination
Peripheral retina in location
Good for night vision, but poor detail
Convergence
Photoreceptors of Vision
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Cones
 Few – about 6 million
 Photopigments sensitive to differing
wavelengths of light
– 400 nm blue
– 500 nm green
– 600 nm red
Photoreceptors of Vision
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Cones
 High level of illumination
 Not very sensitive to light
 See in color
 Precise detail
 Little convergence
 Mostly in center of retina, esp. fovea
Neural Components of Vision
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Bipolar neurons
 Ganglion neurons
 Lateral inhibition
– Horizontal cells
– Amacrine cells
Visual Acuity
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Snellen Eye Chart
 20/20
Light/Dark Adaptation
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Photopigment concentration
 Pupillary light reflex
– PNS constricts pupil
– Direct – ipsilateral
– Indirect = Consensual - contralateral
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Cones inhibit rods in bright light
Visual Pathway
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Optic Nerve
 Optic Chiasma
 Optic tracts
 Thalamus – lateral geniculate body
 Occipital lobe of cerebral cortex