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112 Cards in this Set
- Front
- Back
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thick opaque fibrous white outer covering of the eye
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sclera
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continuous with sheath of optic nerve
tendons of eye muscles attached to it |
sclera
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clear bulging surface in front of the eye
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cornea
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main refractive surface of the eye
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cornea
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What is the Corneal (blink) reflex ?
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Consensual AND Direct Reflex that occurs when cornea is touched (bright light, loud noise will also do the trick)
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What is Corneal astigmatism ?
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abnormal curvature or imperfection in the corneal surface which leads to refractive errors and blurred images
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layer of blood vessels and connective tissue between the sclera (white of the eye) and retina. It supplies oxygen and nutrients to the inner parts of the eye
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choroid
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What are the 2 fluid envts light passes thru between the cornea and retina?
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1) Anterior chamber - aqueous humor
2) posterior chamber - vitreous humor |
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both muscular and vascular tissue, consisting of the cililary muscles and ciliary process
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Ciliary body
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control the shape of the lens giving it refractive power
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ciliary muscles
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secretes aqueous humor, a fluid that fills anterior and posterior chamber and serves to hydrate and nourish lens and cornea; essential for transparent state
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ciliary process
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Failure of adequate aqueous drainage of eye in which high levels of IOP can reduce blood supply to eye and eventually damage retina
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Glaucoma
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collects and drains aqueous humor into venous drainage of sclera
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Canal of Schlemm
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maintains shape of the eye thru fluid production, circulation & re-absorbtion.
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Interocular fluid pressure
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Accomodation: defn
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Dynamic changes in the refractive power of the lens to see up close or far away
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How is accomodation for near objects accomplished?
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Accommodation for focusing on near objects involves the contraction of cillilary muscles, which reduces tension on the zonule fibers (suspensory ligaments) and allows the lens to relax.
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How is accomodation for far objects accomplished?
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Lens assumes flatter shape via zonule fibers
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What are the two opposing forces that determine shape of the lens?
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1) Elasticity of lens (tends to keep it rounded)
2) Tension exerted by zonule fibers thru contraction of ciliary muscles |
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How do zonule fibers relax, allowing for near vision accomodation?
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Sphincter-like contraction of ciliary muscle
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Two layers of the iris
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1) Stroma - contains sphincter and dilator pupillae
2) epithelial pigmented area - gives eye color |
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How is the size of the pupil adjusted?
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GVE component of III, Edinger Westphal
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Mydriasis: ___________
Miosis: ___________ |
dilation;
constriction Of pupil |
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_____ layers of retina contain cell bodies while _______layers contain synapses
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nuclear ;plexiform
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What layer of retina are rods and cones in?
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Inner/outer segment layer
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_________transduce light and terminate on bipolar and horizontal cells.
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Photoreceptors (rods/cones)
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mediate lateral interactions in outer plexiform layers
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horizontal cells
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mediate lateral interactions in inner plexiform layer
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amacrine cells
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terminate on ganglion and amacrine cells.
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Bipolar cells
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are output cells of retina, their axons exit retina at the optic disc or blind spot.
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Ganglion cells
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responsible for light induced changes in photoreceptors
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Cylic GMP channels in the outer segment
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What happens to rods
A) In dark B) In light |
A) In the dark cGMP levels are high, keeping Na channels open--> depolarization of rods
B) In light, absorption of photons causes a decrease of cGMP levels--> Na channels close --> hyperpolarization |
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Rods depolarized in ________ and hyperpolarized in _____.
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dark; light
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T/F light entering the eye passes thru all layers before reaching rods and cones (photoreceptors)
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T
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What is rhodopsin?
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Protein in rods that bleaches in response to light. When it bleaches, it leads to a reduction in Na+ conductance --> hyperpolarization
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What role does glutamate play in visual signal transduction?
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When rods are depolarized, they release glutamate (in dark). When hyperpolarized they stop releasing it.
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In dark, rhodopsin is ______ and glutamate is _______.
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inactive; released
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What are the 3 different cones?
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S, M, and L (short, medium, and long) corresponding to what wavelengths they preferentially respond to. There is overlap
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What is it called when you have all 3 cones types)?
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Trichromat
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Lacking red
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Protanopia
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Lacking green
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Deuteranopia
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Lacking S cone/blue (very rare)
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Tritanopia
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Cones or Rods
A) More sensitive to light B) Specialized for daylight C) High acuity/concentrated in fovea D) Slow response time for dark adaptation E) Fast response time for light adaptation |
A) Rods
B) Cones C) Cones D) Rods E) Cones |
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What are the following:
A) Scotopic B) Mesopic C) Photopic |
They're levels of luminance.
A) Darkest, corresponds to starlight B) Corresponds to moonlight C) Daylight and indoor lighting |
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Rods are active during which luminance levels?
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Scotopic and Mesopic
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Cones are active during which luminance levels?
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Mesopic and Photopic
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What kind of receptors at optic disk?
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NONE
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Where are rods mostly found?
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Periphery of retina
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Genetic disease that Involves loss of rods, eventually leading to only fovea/cones.
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Retinitis pigmentosa
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enlargement of optic nerve caused by increases in ICP
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papilledema
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loss of lens elasticity with age, leading to lessened accomodation
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presbyopia
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Visual areas in temporal lobe are primarily concerned with ___________
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object recognition.
Ventral "what" system. |
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Visual areas in parietal lobe are primarily concerned with ___________
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spatial/motion info.
Dorsal "where" system |
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Visual part of thalamus
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lateral geniculate nucleus
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where ganglion cell axons exit retina
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optic disk
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Optic radiations are part of what?
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portion of internal capsule
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What is the pretectum?
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small area that coordinates the pupillary light reflex
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Where does vision info go once it passes the LGN?
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Goes to striate cortex/primary visual cortex as well as other areas, including SCN
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What is suprachiasmatic nucleus ?
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Area of hypothalamus involved in regulating biological rhythms. Involved in detection of light
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The RIGHT LGN will contain info from what?
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LEFT visual field. So it gets info from NASAL retina of Left eye, and temporal retina of R eye
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Retinal ganglion cells from (nasal, temporal) retina cross the optic chiasm
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NASAL retinal ganglion cells cross (they're processing info from the temporal fields)
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each optic tract contains fibers from the temporal retina of ______eye and nasal retina of __________eye
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ipsilateral; contralateral
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information from the (ipsi, contralateral) hemifield projects to the lateral geniculate nucleus
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contralateral
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What's the role of the superior colliculus?
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Orients movements of head and eyes.
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Layers of LGN
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6 layers.
3-6: parvocellular - P pathway - form and detail 1-2: magnocellular - M pathway - motion |
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What do the parvocellular (3-6) layers of the LGN process?
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P pathway. Process form and detail
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What do the magnocellular (1-2) layers of the LGN process?
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M pathway. Motion.
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Which layers of LGN from ipsilateral eye?
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2,3,5
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Which layers of LGN from contralateral eye?
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1,4,6
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T/F Extrastriate areas play role in integrating visual scene to conscious perception. Each has a “map” of the world. Many of them are distorted such that there’s unequal representation.
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T
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What is Meyer's loop?
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The part of the optic radiations that is in the temporal lobe, and contains fibers representing <b>inferior retinal quadrants (superior visual field)</b>
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What part of optic radiations contains fibers representing the superior visual field (from inferior retinal quadrants)?
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Meyer's loop
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Lesion of Meyer's loop - sx
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Damage to contralateral upper visual fields
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The visual cortex contains a map of the (contra or ipsilateral visual field).
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CONTRA
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What part of visual space is overrepresented?
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The central portion, corresponding to the macula.
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What part of the primary visual cortex represents the UPPER part of the visual field?
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The LOWER part of the cortex (lingual gyrus)
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What part of the primary visual cortex represents the LOWER part of the visual field?
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The UPPER part of the cortex (cuneus)
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Visual cortex has how many layers?
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6
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Which layer of visual cortex receives input from thalamus?
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4
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Which layer(s) send axons back down to thalamus and brainstem/midbrain?
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Layers 5 and 6
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Mixing of the pathways from the two eyes first occurs where?
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striate cortex.
Inputs from the two eyes remains segregated in ocular dominance columns of level 4, but then as layer 4 neurons send axons to other cortical layers, info from two eyes converges onto individual neurons. |
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What are the ocular dominance columns?
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Inputs from the L and R eyes remains segregated because axons of LGN neurons terminate in alternating eye-specific columns withing cortical layer IV. These are the ocular dominance columns.
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What are the blobs?
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Groups of color sensitive cells
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What are orientation-selective neurons?
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Certain neurons in visual cortex respnd most vigorously to bars in certain arrangements/orientations within the cell's receptive field. The responses are cortical neurons are thus tuned to the orientation of edges.
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The dorsal/where pathway is associated with what cell type in LGN?
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Magnocellular
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The ventral/what pathwy is associated with what cell type in LGN?
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Parvocellular
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What is an agnosia?
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defect in recognition or meaning without a loss in the objective sensation. Not a sensory loss, it is the inability to recognize or attach meaning to stimuli.
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inability to recognize familiar objects by visual means; readily recognized when nonvisual cues are available. Can be very specific:
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visual agnosia
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3 components of the <b>near response</b>
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1) Accomodation : ciliary m contracts to thicken lens.
2) Convergence: medial rectus contracts 3) Pupillary constriction |
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Involuntary blinking of the eyelids elicited by stimulation (such as touching or a foreign body) of the cornea, or bright light or loud noise
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Corneal/blink reflex
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Afferent limb of corneal/blink reflex carried by what CN?
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V1 (ophthalmic trigeminal)
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Efferent limb of corneal/blink reflex carried by what CN?
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CN VII / Facial
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T/F Corneal/blink reflex is consensual
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T
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When one eye is exposed to light, the pupils of both eyes constrict
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Pupillary response
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consensual pupillary light response
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Accompanied constriction of pupil when light is shone into the OTHER pupil
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Afferent limb of pupillary light reflex
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Optic nerve sends retinal ganglion fibers to pretectum which sends fibers to Edinger-Westphal nucleus
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Efferent limb of pupillary light reflex
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Edinger-Westphal nucleus sends preganglionic parasympathetic fibers to ciliary ganglion via CN III (oculomotor) --> postganglionic parasympathetics innervate pupillary constrictor muscles
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Edinger Westphal nucleus involved in what?
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Origin of preganglionic parasympathetic fibers to ciliary ganglion via CN III (oculomotor) --> postganglionic parasympathetics innervate pupillary constrictor muscles.
Efferent limb of pupillary light reflex |
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Pretectum role
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region of neurons found between the thalamus and midbrain. It receives binocular sensory input from retinal ganglion cells of the eyes, and is the region responsible for maintaining the pupillary light reflex. Output is to Edinger-Westphal nucleus
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Argyll Robertson pupils
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bilateral small pupils that constrict when the patient focuses on a near object (they “accommodate”), but do not constrict when exposed to bright light (they do not “react” to light).
AKA prostitute's pupils |
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What is Adie's tonic pupil syndrome?
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caused by damage to the postganglionic fibers of the parasympathetic innervation of the eye, usually by a viral or bacterial infection which causes inflammation, and characterized by a tonically dilated pupil.
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Anisocoria
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unequal pupils
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Miosis
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refers to the constriction of the pupils.
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Mydriasis
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refers to dilation of pupils
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What change to vision would occur if the following happened:
Lesion one optic nerve |
Monocular vision
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What change to vision would occur if the following happened:
Lesion optic chiasm |
Fibers crossing in optic chiasm include those from nasal region of each retina, which process the temporal visual fields. It would lead to <b>loss of temporal visual fields</b>.
<b>bitemporal heteronymous hemianopsia</b> |
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Anopsia: defn
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defect in the visual field
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Hemianopsia : defn
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type of anopsia where the decreased vision or blindness takes place in half the visual field of one or both eyes
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homonymous hemianopsia
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loss of half of the visual field on the same side in both eyes
homonymous = the same hemianopsia = defect affecting half of visual field |
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What change to vision would occur if the following happened:
Lesion one side of optic tract |
Would lose contralateral visual field because you'd lose the ipsilateral temporal retina and contralateral nasal retina, which are processing the same visual field.
<b>contralateral homonymous hemianopsia</b> |
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What change to vision would occur if the following happened:
Lesion one side of optic radiations |
contralateral homonymous hemianopsia
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What change to vision would occur if the following happened:
Lesion to one cuneus gyrus |
<b>contralateral inferior quadrantanopsia</b>
The cuneus gyrus is superior to lingual gyrus and processes INFERIOR visual field (from SUPERIOR part of retina). Therefore, the INFERIOR parts of BOTH visual fields would be gone |
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What change to vision would occur if the following happened:
Lesion to one lingual gyrus (or meyer's loop) |
contralateral superior quadrantanopsia
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