The Human Eye

Name: __________________ Topic: Eye LO:Describethestructureof theeyeasseeninfrontviewandinhorizontalsection ● Eacheyeballis attachedto theskullby rectusmuscles, whichcontroleyemovement.● The eye consists of 3 layers,sclera, choroid andretina(innermost).o Thesclerais coveredbya thinlayerof transparentmucusmembranecalled theconjunctiva, covering the sclera, keepingtheeyeball moist.o Scleraprotectsthe eye.o Choroidcontainsnumerousbloodvesselsto transportoxygenandnutrientsto the eye andremove metabolic waste products.o Retinahasphotoreceptorscalledrodsandconesthatdetectslightandwhere images are formed▪ Rodsenables us to see indim light,imagesin blackand white ▪ Conesenablesusto seecoloursin brightlight; availableinred,blue and green.o Fovea(yellowspot)isthesitewhereimagesarefocused.Itcontainsthemost number of photoreceptors. Concepts Summary NotesNan Hua High School Biology 1

Name: __________________ Topic: Eye o Corneais transparentanddome-shapedto refractlightintotheeyetofocus on the retina.● Irisis a circularsheetof muscles,consistingof circularmusclesandradialmuscleswhichworksantagonisticallywhichcontrolsthesizeofthepupilandtheamountof lightenteringthepupil. It containspigment,whichgivestheeyeitscolour.● Pupilis a hole in the center of the iris which allowslight to enter.● Blindspotis the site at whichthe opticnerveleavesthe eyeandnophotoreceptorsarepresent. Opticnervetransmitsnerveimpulsesviasensoryneuroneto thebrain.● Lenscontrolstherefractionof lightandfocuseslightraystoforma clearandsharpimage on the retina atvarying distances.● Ciliarymusclesfoundintheciliarybodycontrolsthethickness/curvatureofthelens.● Suspensoryligamentsattachesthelenstotheciliarymuscles/transmitstheforcefrom the ciliary muscles to the lens. LO:Statetheprincipalfunctionsofcomponentpartsoftheeyeinproducingafocused image of near and distant objects on the retina Producinga focusedimageofnearobjectsontheretina&interpretationoftheimage by the brain Concepts Summary NotesNan Hua High School Biology 2

Name: __________________ Topic: Eye ● Ciliarymusclesin ciliarybodycontract, relaxingthepullonthesuspensoryligaments.● Suspensory ligaments slackens, relaxing their pullon the lens.● Lens becomesthicker and more convex, decreasing itsfocal length.● Lightraysfromnearobjectsbendmoreandfocusto a pointontheretina,forming aclear and sharp image.● Photoreceptorsontheretinaarestimulated,generatingnerveimpulseswhicharetransmittedby sensoryneuronein the opticnerveto thebrainwhichinterprets the nerve impulses and the person sees the near object.● Thepointatwhichtheimageofanearobjectbecomesblurrediscalledthenearpoint of visionwhere thelens reaches its maximumcurvature. Producingafocusedimageofdistantobjectsontheretina&interpretationoftheimage by the brain ● Ciliary musclesin the ciliary bodyrelax, pullingon the suspensory ligaments.● Suspensory ligaments becomes taut, pulling on theedge of the lens.● Lens becomesthinner and less convex, increasing itsfocal length.● Lightraysfromthedistantobjectbendlessandfocustoa pointontheretina,forming aclear and sharp image. Concepts Summary NotesNan Hua High School Biology 3

Name: __________________ Topic: Eye ● Photoreceptorsontheretinaarestimulated,generatingnerveimpulseswhicharetransmittedby sensoryneuronein the opticnerveto thebrainwhichinterprets the nerve impulses and the person sees the distant object. LO: Describe the pupil reflex in response to bright and dim light Pupilreflexistheinvoluntaryactionofthemusclesintheirisinresponsetoachangeinlight intensitybychanging the size of the pupil. Thisactionis controlledbytwosetsof involuntarymusclesintheiriscalledcircularmusclesandradial muscles. Pupil Reflex Pathway● Change in the light intensitystimulatesphotoreceptorson the retina.● Nerveimpulsesaregeneratedandtransmittedalongthesensoryneuroneintheopticnerveacrossa synapseto therelayneuronein thebrainandacrossanothersynapsetothemotorneuroneandtotheeffector whicharethecircularand radial muscles of the iris.In bright light● Circular muscles of iris contractandradial musclesof iris relax● Pupilconstrictsandlesslightenterstheeyetopreventphotoreceptorsontheretina from being damaged In dim lightConcepts Summary NotesNan Hua High School Biology 4

Name: __________________ Topic: Eye ● Circular muscles of iris relaxandradial muscles of iris contract● Pupildilatesandmore lightenters the eye Concepts Summary NotesNan Hua High School Biology 5