Sensation vison

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Sensation vison

  1. 1. SENSATIONSENSATION  SENSE a physical system thatSENSE a physical system that receives a particular kind of physicalreceives a particular kind of physical stimulation and translate it into anstimulation and translate it into an electrochemical message the brainelectrochemical message the brain can understandcan understand  SENSATION message our brainsSENSATION message our brains receives from a sensory receptorsreceives from a sensory receptors that has stimulatedthat has stimulated
  2. 2. Sense of VisionSense of Vision
  3. 3. Light is the form of electromagnetic energy thatLight is the form of electromagnetic energy that the receptors of our eyes are distinctivelythe receptors of our eyes are distinctively designed to receivedesigned to receive..
  4. 4. Parts of the Eyes and its FunctionsParts of the Eyes and its Functions  CorneaCornea- is a clear membrane just in- is a clear membrane just in front of the eye.front of the eye. -is a curved exterior lens that-is a curved exterior lens that gathers and focuses the enteringgathers and focuses the entering light.light.  PupilPupil- the hole in the center of the- the hole in the center of the eye.eye.
  5. 5.  IrisIris- is the circular muscle that gives our- is the circular muscle that gives our eyes its distinctive colors.eyes its distinctive colors. *bright light- iris constrict*bright light- iris constrict *dim light- iris is dilated*dim light- iris is dilated  lenslens- focusing images from multiple- focusing images from multiple distances.distances. -causes light to bend as it passes through it.-causes light to bend as it passes through it. -A transparent and somewhat flexible disk--A transparent and somewhat flexible disk- like entity filled with a gelatinous materiallike entity filled with a gelatinous material -Curved interior which causes bending of-Curved interior which causes bending of light waves.light waves.
  6. 6.  The RetinaThe Retina—a network of neurons—a network of neurons that extends over most of the backthat extends over most of the back surface of the interior of the eye.surface of the interior of the eye. -retina is where electromagnetic light-retina is where electromagnetic light energy is transduced into neuralenergy is transduced into neural electrochemical impulses.electrochemical impulses. *photoreceptors-transduce light*photoreceptors-transduce light energy into electrochemical energy.energy into electrochemical energy. Photoreceptors can be found in thePhotoreceptors can be found in the third layer of the retina.third layer of the retina.
  7. 7. Types of PhotoreceptorsTypes of Photoreceptors RodsRods—are long and thin receptors—are long and thin receptors responsible for vision in dim light.responsible for vision in dim light. -do not receive color.-do not receive color. ConesCones-are short and thick-are short and thick photoreceptors responsible for visionphotoreceptors responsible for vision in bright light.in bright light. - receive color.- receive color. - there are 6 million cone cells in- there are 6 million cone cells in human eyes.human eyes.
  8. 8.  Blind SpotBlind Spot is the small area on theis the small area on the retina where the optic nerve pushesretina where the optic nerve pushes aside photoreceptors to exit theaside photoreceptors to exit the eyes.eyes.  Visual cortexVisual cortex—from the thalamus,—from the thalamus, neurons carry information to theneurons carry information to the primary visual cortex in the occipitalprimary visual cortex in the occipital lobe of the brain.lobe of the brain.
  9. 9. Color Vision has two main theories:Color Vision has two main theories: trichromatic theory and opponent theory.trichromatic theory and opponent theory. Trichromatic theoryTrichromatic theory states that color perception isstates that color perception is produced by three types of receptors (cone cells inproduced by three types of receptors (cone cells in the retina)—green, red, and blue.the retina)—green, red, and blue. Opponent-process theoryOpponent-process theory states that cells in thestates that cells in the visual system respond to either red-green or blue-visual system respond to either red-green or blue- yellow colors; a given cell might be excited by redyellow colors; a given cell might be excited by red and inhibited by green, whereas another cell mightand inhibited by green, whereas another cell might be excited by yellow and inhibited by blue.be excited by yellow and inhibited by blue.
  10. 10. Visual ImpairmentsVisual Impairments  What is a cataract?What is a cataract? A cataract is aA cataract is a clouding of the clear lens in the eye and isclouding of the clear lens in the eye and is one of the leading causes of visionone of the leading causes of vision impairment.impairment.  GlaucomaGlaucoma is a disease caused byis a disease caused by increasedincreased intraocular pressureintraocular pressure (IOP)(IOP) resulting either from a malformation orresulting either from a malformation or malfunction of themalfunction of the eye’s drainage structureseye’s drainage structures. Left untreated,. Left untreated, an elevated IOP causes irreversiblean elevated IOP causes irreversible damage thedamage the optic nerveoptic nerve and retinal fibersand retinal fibers resulting in a progressive, permanent lossresulting in a progressive, permanent loss of vision.of vision.
  11. 11.  FarsightednessFarsightedness oror hyperopiahyperopia, occurs, occurs when light entering the eye focuses behindwhen light entering the eye focuses behind thethe retinaretina, instead of directly on it. This is, instead of directly on it. This is caused by acaused by a corneacornea that is flatter, or an eyethat is flatter, or an eye that is shorter, than a normal eye.that is shorter, than a normal eye. Farsighted people usually have troubleFarsighted people usually have trouble seeing up close, but may also have difficultyseeing up close, but may also have difficulty seeing far away as well.seeing far away as well.
  12. 12. Nearsightedness or myopia, occurs when lightNearsightedness or myopia, occurs when light entering the eye focuses in front of theentering the eye focuses in front of the retinaretina instead of directly on it. This is caused by ainstead of directly on it. This is caused by a corneacornea that is steeper, or an eye that is longer,that is steeper, or an eye that is longer, than a normal eye. Nearsighted people typicallythan a normal eye. Nearsighted people typically see well up close, but have difficulty seeing farsee well up close, but have difficulty seeing far away.away.
  13. 13. Astigmatism means that theAstigmatism means that the corneacornea is oval like ais oval like a football instead of spherical like a basketball. Mostfootball instead of spherical like a basketball. Most astigmatic corneas have two curves – a steeperastigmatic corneas have two curves – a steeper curve and a flatter curve. This causes light to focuscurve and a flatter curve. This causes light to focus on more than one point in the eye, resulting inon more than one point in the eye, resulting in blurred vision at distance or near. Astigmatismblurred vision at distance or near. Astigmatism often occurs along withoften occurs along with nearsightednessnearsightedness oror farsightednessfarsightedness..

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