EXP Exam 4 Study Questions Vision I 1 What does the visual spectrum refer to Even if we can t see it is there other electromagnetic radiation that we somehow respond to Know an example of an animal that uses more of the electromagnetic spectrum The visual spectrum refers to the 380 760nm that we can see and as wavelengths change the color we observe changes There is also UV rays which can cause humans sunburns and Infrared which allows us to see when using night vision EX Pit vipers rattlesnakes can detect infrared radiation 2 FYI of photons perception of intensity wavelength perception of color 3 Slide 5 know the terms in red Radiance energy from source intensity of a light beam the sun radiates light Illuminance energy from source to object the amount of light falling onto patch of unit surface area the sun illuminates the Earth When the light hits the surface it can be reflected absorbed or transmitted 1 2 3 If a surface looks lighter it is reflecting most of the light If a surface looks dark it is absorbing most of the light If transmitted some is refracted bent 1 Such as when light goes into thru the water or the eyeball 4 Know the parts of the eye Be able to label them on a picture and know what they each do The Eye basic functions Control light entry how much light is able to come thru the eye and get to the retina Focus light on receptors in retina Visual transduction photons electrical 1 Transparent tissue covering the front of the eye 2 Continuous with sclera protective coating around back 5 6 of Cornea eye 3 Light is transmitted refracted thru this 4 No blood vessels 5 Nerve endings important to detect touch and to force eye to close produce tears if the cornea is scratched to preserve transparency 6 CNs afferent branch is trigeminal V efferent is facial VII Aqueous humor 1 Fluid derived from blood just behind cornea 2 Supplies oxygen nutrients to cornea lens 3 Removes waste from cornea lens 4 Helps maintain shape of eye intraocular pressure too much production or too little drainage in glaucoma Crystalline Lens Lens 1 Transparent tissue 2 Bends light that is passing through the eye to focus image on retina Pupil Iris Iris the size of the pupil therefore controls light entry Circular band of muscles dilator sphincter that controls 1 1 Pigmentation of the iris gives color to the eye can pass Choroid Vitreus Humor 2 Very complex better for i d than fingerprints Hole in the center of the iris where light passes through 2 Pupil 3 Size of pupil dilated or constricted determines how much light 1 Layer of blood vessels providing nutrition for the eye 2 Heavily pigmented high melanocyte content so absorbs extraneous light entering eye this reduces reflection within eye would blur image 3 Attached to sclera 1 Between lens and retina 2 Clear jelly like fluid 3 80 of internal volume of eye 4 Refracts light 5 Maintains shape of the eye 6 Floaters bits of biodebris that drift around in vitreus you see them maybe in bright light 1 Layer of tissue on back of the eye 2 Like an outgrowth of the brain same embryonic tissue 3 Nerve cells and photoreceptors rods cones to absorb light photons and transduce it to neural activity Retina 4 Ganglion cells whose axons leave the back of the eye and create the optic nerve 5 Only part of the body where we can see arteries and veins directly so good diagnostic for entire vascular system 5 What is the pupillary light reflex What cranial nerves are involved Why does red eye occur in photographs The pupillary light reflex Whytt s reflex is the immediate constriction of pupil in response to bright light CNs II afferent and III efferent Red eye typically occurs when the light is dim and the bright flash from a camera causes the pupil to dilate When this happens sometimes too much light is let in and it is reflected back from the fundus thru choroid latter gives reflection of a red appearance 6 What is accommodation how is it accomplished What shape do you need your lens flat or bulging to see close by What about to see far away What is presbyopia what causes it 1 Accommodation changing it s curvature in order to bend the light More or Less near far focus 2 3 How does it bend light By bending itself control its curvature 1 Ciliary muscles a Zonules of Zinn Why do we need to accommodate Light enters eye refracted converges at a point on the retina Light rays from object 20 feet away are parallel Light rays from closer object are divergent and must be sufficiently refracted or will not meet on a single focal point So as opposed to other parts of the eye the refractive power of the lens is dynamic Ability to accommodate decreases with age 1 2 Presbyopia By 40 50 yr old can t accommodate enough to focus on things within arm s reach Why Lens becomes harder and capsule surrounding it loses elasticity Some vertebrates like fish accommodate by moving lens in relation to retina 1 Like camera lens move forward to focus on nearby object back to focus on distant object 7 What are cataracts What causes them How do they affect vision Opacities in the lens caused by irregularity in the crystallins densely and regularly packed proteins that make up the lens and whose organization dense regular gives the lens its translucence Different types different locations which of the many layers of the lens Interfere w vision b c absorb and scatter more light than the normal lens Causes risk factors congenital rare age related usually after 50 in most people after 70 diabetes being struck by lightening penetrating or non penetrating eye trauma sun exposure 8 What are emmetriopia hyperopia myopia Emmetriopia perfectly matched to the length of the eyeball no refractive error b c the refractive power of the eye is 1 Ability to refract light is perfectly matched to the length of the eye Myopia near sightedness 1 eyeball is too long for refractive power of eye so focus image in front of retina instead of on it star looks like a blur 2 Correct with negative minus concave lenses which diverge the Hyperopia rays before they enter the eye far sightedness 1 Eyeball is too short for refractive power of eyes so focus behind retina again star looks like a blur If young can correct by accommodating 1 2 Correct with plus convex lenses to converge rays before they enter the eye 3 Most newborns are hyperopic b c optical components of eyes are well developed at birth compared w length of eyeballs 9 What is an astigmatism Occurs when cornea isn t spherical it may be curved more steeply in one
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