· Eye Diagrams
· Structure of the Eyeball- layers, photoreceptors
-fibrous
-outermost layer; dense avascular connective tissue
-2 regions: sclera and cornea
-vascular
-middle pigmented layer
-3 regions: choroid, ciliary body, and iris
-sensory
-retina: outer pigmented layer, neural layer (photo receptors: transduce light energy)
-photoreceptors:
-rods: more numerous at peripheral region of retina, away from the macula lutea; operate in dim light; provide indistinct, fuzzy, non color peripheral vision
-cones: found in the macula lutea; concentrated in the fovea centralis; operate in bright light; provide high-acuity color vision
· Pathway of light entering the eye
-cornea, aqueous humor, lens, vitreous, humor, neural layer of retina, photoreceptors
· Focusing for Close Vision
-light from a close object diverges as it approaches the eye
-requires that the eye make active adjustments
-accommodation: changing the lens shape by ciliary muscles to increase refractory power
-constriction: pupillary reflex constricts the pupils to prevent the most divergent light rays from entering the eye
-convergence: medial rotation of the eyeballs toward the object being viewed
· Emmetropic, myopic, hyperopic
-emmetropic: normal; focal point is on retina
-myopic: nearsighted; focal point is in front of retina
-hyperopic: farsighted; focal point is behind retina
· Ear Diagram- outer, middle and inner
· Properties of sound
-pitch
-perception of different frequencies
-normal range is from 20-20000 Hz
-the higher the frequency, the higher the pitch
-loudness
-subjective interpretation of sound intensity
-normal range is 0-120 decibels (dB)
· Transmission of sound to the internal ear
-sound waves vibrate the tympanic membrane
-ossicles vibrate and amplify the pressure at the oval window
-pressure waves move through perilymph of the scala vestibuli
· Static and Dynamic Equilibrium
-vestibular receptors monitor static equilibrium
-semicircular canal receptors monitor dynamic equilibrium
· Homeostatic Imbalances- Cataracts, Glaucoma, Macular Degeneration, Deafness
-cataracts
-clouding of the lens
-age related hardening or thickening
-risks: diabetes, smoking, exposure to intense sunlight
-vitamin c benefits
-surgical removal
-glaucoma
-pressure build up in the eye, puts pressure on the retina and optic nerve
-inherited
-causes blindness
-pressure test
-eye drops to lower pressure
-macular degeneration
-progressive deterioration of the retina
-main cause of vision loss over 65
-deafness
-conduction
-sensorineural
-cochlear implants: cochlear damage, convert sound wave into electrical signal