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138 Cards in this Set
- Front
- Back
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Cones are for
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Color vision
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Rods are for
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night vision
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What are the 10 layers of the retina
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pigmented layer, layer of rods and cones, outer and inner nuclear layer, outer and inner nuclear layer, ganglion cell layer, layer of optic nerve fiber, stratum opticum
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2 function of pigmented epithelial cells
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absorb stray light and prevent scatter and convert 11-cis retinal to all-trans
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Blind spot does not have
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rods and cones
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Bipolar cells synapse
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rods and cones to ganglion
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how many cones synapse on a single bipolar cell, how does this account for acuity and sensitivity?
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few, high acutiy and low sensitivity
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how many rods synapse on a single bipolar cell, how does this account for acuity and sensitivity?
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many, less acutiy and greater sensitivity
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what forms local circuits with bipolar cells?
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horizontal and amavrine cells
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what are the output cells of retina
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ganglion cells
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what forms the optic nerve relative to the eye
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axons of the ganglion cells
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What does the fovea contain
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only cones which aid in detal
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What is the area of greatest visual acuity
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fovea
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Rods or cones, which adapts first to the dark
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cones
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Rods or cones, which is primary for night vision
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rods
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What in the pigment found in the retina
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melanin
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what is the function of the pigment in the retina
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prevent diffuse scattering of light
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What vitamin is stored in the pigmented layer
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vit a
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what is vit a important for
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it is a precursor of the photosensitive chemicals of rods and cones
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What is the blood supply to the retina
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central retinal artery
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Where does the central retinal artery enter the eye
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via the optic nerve
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What does light convert 11-cis retinal to
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all-trans retinal via photoisomerization
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What is an intermediate of photoisomerization
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metarhodopsin II
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Without vit a what condition can this cause?
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night blindness
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What G protein does metarhodopsin II activate?
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transducin
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What does transducin activate
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phosphodiesterase
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What does phosphodiesterase catalyze
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the conversion of syslic guanosine monophosphate to 5""-GMP and cGMP levels dec
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Dec levels of cGMP cause what
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closure of Na+ channels, dec inward Na+ and results in hyperpolarization
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If neurotransmitter is excitatory the response is
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hyperpolarization
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If neurotransmitter is inhibitory the response is
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excitation
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Color blindness is characterized by
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a lack of a particular type of cone
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Protanope
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is a lack of red cone
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Deuteranope
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is a lack of green cone
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In dark conditions retinal is converted back to
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rhodopsin
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in 20/20 vision what does the first number represent?
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the first number is always 20 and it represents where you were standing when you were able to correctly read all the letters of a particular line on the eye chart
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How does the superior and inferior obliques move the eye?
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rotates
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How does the medial and lateral recti move the eye?
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side to side
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How does the superior and inferior recti move the eye
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up and down
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What is the basic visual pathway
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thru cornea thru aqueous humor thru iris and then lens to retina
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how is the image presented on the retina
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inverted
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What does the suprachiasmatic nucleus of the hypothalamus control?
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circadian rhythms
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What does the pretectal nuclei control
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pupillary light reflex and accommodation of the lens
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What does the superior colliculus control
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rapid directional movement of both eyes
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What does the ventral lateral geniculate control
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the bodies behavioral functions
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What are the 2 functions of the dorsal lateral geniculate nucleus (aka lateral geniculate body) do
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relay and gate control
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What does layers II, III, and V of DLGB do in the relay of information to primary visual contex
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recieve information from lateral half of ipsilateral retina
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Where are the layers I, IV, and VI come from of the DLGB
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Medial half
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What is the name of layer I and II
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magnocellular layer
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What is the magnocellular layers function
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its a large Y retinal ganglion cell and is poor conduction to V1. makes color blind images in B&W
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What layers compose the parvocellular layers
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small to medium X retinal cells, coderate conduction vel and good for point to point
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Where is the primary visual cortex located
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in the medal occipital lobe in the calcarine fissure region
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What is scotomata
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blind spot in field of vision, usually from glacoma
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What is retinitis pigmentosa
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associated with retinal degreneration, melanin deposits will form in the retina, usually laterally first and then more central
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What is horners syndrome
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a sympathetic output interrupted. The pupil remains constricted, superior eyelid droops, seating does not occur on that side of face.
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What is argyll-robinson pupil
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associated with neurosyphilis, lens accommodates but pupil does not react to light, prostitute eye
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How does miosis of the left eye present
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medial deviation
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The degree of refraction increase as
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the difference in TI increases and the degree of angulation increases
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Describe the light reflex
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controls amount of light entering eye by adjusting diameter of pupil, activation of retinal azons, ehich excites pretectal neurons, and in turn innervate ipsilateral and contralateral edinger-westphal neurons
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From the deinger-westphal neurons, where does the signal get sent to
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preganglionic fibers via a branch of oculomotor nerves to excite the ciliary ganglia of both sides.
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What does the ciliary ganglia postganglionic parasympathetic axons release?
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acetylcholine to activea pupillary constrictor muscles of the iris
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How does convex lens bend light
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more at the edges lending to converge on a focal point
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How does concave lens bend light
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diverges proportional to the lens angle leading to divergence
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What is refractive power
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how powerfully it bends light
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What is refractive power measured in
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diopters
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1 diopter vs 10 diopters
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10 d is short and powerfuland lens is thicker
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What does the variable aperture allow
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various amounts of light to enter the eye
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What does accommodation allow
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various refractive power to focus
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Where does 2/3 of the refractive power of the eye come from
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the surface of the cornea
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What is the lens held in place by
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Suspensory ligament
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When the lens contracts how does the shape of the lens change
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becomes more sperical
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When the lens becomes more spherical, how does this affect the power of the lens?
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increases the refractive power
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What is presbyopia
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an inability to accommodate
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What is astigmatism
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abnormal optical properties of the eye in which light form an objuect entering the eye in different planes and focus at different points on the front or behind the retinal resulting in blurred vision
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Hyperopia is seen in
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far sightedness
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Myopia is seen in
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near sightedness
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Hyperopia is characterized by
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Eyeball too short and lens too weak
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Myopia is characterized by
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eyeball is too long and lens is too strong
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How is myopia corrected
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concave lens
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How is hyperopia corrected
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convex lens
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What is prebyopia
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special case of hyperopia; lens loses elasticity
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What are cataracts caused by
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coagulation of lens proteins
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Where is aqueous humor found?
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in front of the lens
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Where is vitreous humor found?
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behind the lens
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Where is the formation of aqueous humor?
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Produced by ciliary processes, flows between ligaments of the lens, through the pupil into the anterior chamber, goes between the cornea and the iris, through a meshwork of trabeculae, and enters the canal of schlemm
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Where is the formation of aqueous humor found?
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Ciliary processes
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How is intraocular pressure determined?
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resistance to outflow of aquous humor in the canal of schlemm
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How can an increase of intraocular pressure cause blindness?
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compression of axons of optic nerve
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How can glaucoma cause blindness?
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inc WBCs in fluid which plug up trabeculea. the axons of the optic nerve get compressed at the optic disk where they enter the eye
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What is retrolental fibroplasia
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toxicity of therapeutic oxygen which can lead to blindness
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What is conjunctivitis
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commonly caused by adenovirus
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What is senile macular degeneration
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loss of central vision and pigmentary changes or hemorrhage in the macula
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What is retinoblastoma
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malignant retinal tumor of childhood
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What is a characteristic of retinitis pigemtosa?
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loss of rods and later loss of cones; hereditary night blindness
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Olfactory nerve is what CN
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I
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olfactory system is only sensory system without any
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precortical relay in the thalamus
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Characteristics of CN I
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Axons of the olfactory nerves are unmyelinated C fibers and are among the smallest and slowerst in the nervous system
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What is the olfactory epithelium is also innervated by
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CN V (trigeminal) and detects noxious and painful stimuli
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Fracture to the cribiform plate will not affect
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CN V thus can still smell ammonia
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The axons that enter the olfactory bulb and synapse in the olfactory glomeruli with
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mitral and tufed cells
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olfactory track projects to the contralateral olfactory tract via the
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anterior commissure
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the lateral olfactory stria projects to the
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primary olfactory cortex and amygdaloid nucleus
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the primary olfactory cortex
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overlies the uncus of the parahippocampal gyrus
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The primary olfactory cortex consists of
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prepiriform and periamygdaloid cortices
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The mediodorsal nucleus of the thalamus
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projects to the orbitofrontal cortex where the conscious perception of smell takes place
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Steps in transduction in olfactory receptor neurons
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mol binds with receptor, activeate G protein which activates adenylate cyclase, inc in intracellular cAMP that opens Na channels and produces depolarizing receptor potential, receptor potential depolarizes the initial segment of the axon to thresold and action potientials are generated and propagated
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What is anosmia
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loss of sense of smell
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Olfactory n may be damaged by
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fracture of the cribriform plate
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olfactory hallucination may be consequence of
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lesions of the parahippocampal uncus
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Foster kennedy syndromes results from
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menigioma of the olfactory groove which compressin the olfactor and optic nerve.
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Foster kennedy syndrome results in
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ipsilateral anosmia, optic atrophy, and contralateral papilledema
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Olfactory pathways are closely related to the
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limbic systems
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Taste buds occur in groups on
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papilae
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Taste receptor cells are
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modificed epithelial cells
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What are the first order neurons in taste
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CN VII, CN IX, and CN X
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Where do the first order neurons project to
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centrally via the solitary tract
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the solitary nucleus receives taste input from the
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tongus and epiglotis
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The parabrachial nucleus of the pons
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receives taste input from the solitary nucleus and projects tats input to the hypothalamus and amygdala
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the ventral posteromedial nucleus
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projects to the gustatory cortex of the parietal operculum and parainsular cortex
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The gustatory area is located at the
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inferior end of the postcentral gyrus and extends into the anterior insula
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Fungiform papillae
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mushroom-like sutructure several hundreds of which are present on the anterior two thirds of the tongue
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Foliate papillare are
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folded structure on the posterior edge of the tongue and their taste buds respond best to sour stimuli
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the taste buds on fungiform and foliate papillae are
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innervated by the chorda tympani branch of the facial nerve
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circumvallate papilae
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large round structures encircled by a depression which respond to bitter substances and innervated by CN IX
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von ebners glands are
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present in the circumvallate papillae and secretes mucus in its clefts
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taste buds in the region of the epiglottis and upper esophagus are innervated by
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CN X
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Somatosensory and frontal cortex in response to taste
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conscious perception of tates
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Amygdala hypothalamus in response to taste
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emotional quality of tatse
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Hippocampus in response to taste
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memories of tastes
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What is ageusia
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gustatory anesthesia or lack of sense of taste; commonly caused by heavy smoking; freq associated with peripherial lesions of CN VII and disease of middle ear CN IX
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Foliate papillare are
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folded structure on the posterior edge of the tongue and their taste buds respond best to sour stimuli
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the taste buds on fungiform and foliate papillae are
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innervated by the chorda tympani branch of the facial nerve
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circumvallate papilae
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large round structures encircled by a depression which respond to bitter substances and innervated by CN IX
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von ebners glands are
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present in the circumvallate papillae and secretes mucus in its clefts
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taste buds in the region of the epiglottis and upper esophagus are innervated by
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CN X
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Somatosensory and frontal cortex in response to taste
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conscious perception of tates
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Amygdala hypothalamus in response to taste
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emotional quality of tatse
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Hippocampus in response to taste
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memories of tastes
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What is ageusia
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gustatory anesthesia or lack of sense of taste; commonly caused by heavy smoking; freq associated with peripherial lesions of CN VII and disease of middle ear CN IX
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