ZOO161 Notes - 11:04:00 AM Types of Receptors Mechanoreceptors touch pressure hearing Thermoreceptors temperature Photoreceptors light(vision

04/03/2008 10:04:00 • Types of Receptors • Mechanoreceptors  touch, pressure, hearing • Thermoreceptors  temperature • Photoreceptors  light (vision) • Chemoreceptors  activated by chemicals for smell and taste • Pain Receptors  physical or chemical trauma to tissue • Referred Pain  feeling pain of internal organs in distant location (nerves combine at spinal cord) • The Eye • Photoreceptors change light to chemical signal transmitted to the brain • Light goes from the lens to the retina (photoreceptors); the lens focuses light on the retina; the retina transforms the light to a chemical signals • Fovea  a high concentration of photoreceptors, which allows us to see details • Optic Nerve  transfers chemical signal to occipital lobe • Vitreous humor  behind the lens in front of the retina (never replaced) • Aqueous humor  in front of lens replaced constantly; nourishment (is replaced) • The Ear • Pinna  outer ear; funnel sound into auditory canal • Eardrum  tympanic membrane; vibrates in response to sound • Malleus } • Incus } vibrate (amplify vibrations) • Stapes }

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• Cochlea  vibrated by ear bones through the oval window o Hair cells move to activate sensory neurons • Vestibular Apparatus  correct head position relative to the rest of the body • Special Senses • Smell • Vision • Hearing • General Senses • Touch • Pressure • Internal Senses • Eye Disorders • Glaucoma  drainage of aqueous humor blocked (increase of fluid = an increase in pressure) • Cataracts  “cloudiness” of the lens; light cannot penetrate • Macular Degeneration  decrease in photoreceptors (in fovea) results in a progressive loss of vision (can tell there is a face, but cannot point out certain features [nose, mouth, eyes, etc.]) • Nearsightedness  loss of vision far away (light is focused in front of retina) • Farsightedness  loss of vision close to you (light is focused behind retina) • Ear Disorders • Conductive Hearing Loss  blockage in sound movement o Causes:  Wax  Infections 