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Chapter 10 Special Senses © 2009 Delmar, Cengage Learning Special Senses • • • • • Touch Vision Hearing Smell Taste © 2009 Delmar, Cengage Learning Sensory Receptors • Stimulated by changes in the environment • Generalized in body – Touch, pain, temperature and pressure (proprioceptors) © 2009 Delmar, Cengage Learning Sensory Receptors • Specific receptors – – – – Taste buds of the tongue In the nose In the retina of the eye In the inner ear (organ of Corti) © 2009 Delmar, Cengage Learning The Eye • Tender sphere about 1 inch (2.5 cm) in diameter • Protected by orbital socket, eyebrows, eyelids, and eyelashes • Lacrimal duct and glands © 2009 Delmar, Cengage Learning The Eye • • • • Oil glands Conjunctiva Stereoscopic vision The wall of the eye has three layers – Sclera – Choroid – Retina © 2009 Delmar, Cengage Learning The Eye © 2009 Delmar, Cengage Learning Sclera • Outer layer of the eye which is the white of the eye • Fibrous capsule maintains shape and protects • Extrinsic muscles © 2009 Delmar, Cengage Learning Extrinsic Muscles • • • • • • Superior rectus Inferior rectus Lateral rectus Medial rectus Superior rectus Inferior oblique © 2009 Delmar, Cengage Learning Cornea • Circular clear area in front center of the sclerotic coat • Transparency allows passage of light rays • Five layers • Very sensitive to pain and touch © 2009 Delmar, Cengage Learning Choroid Coat and the Iris • Middle layer of the eye • Blood vessels to nourish the eye • Nonreflective pigment rendering it dark and opaque • Circular opening called the pupil © 2009 Delmar, Cengage Learning Choroid Coat and the Iris • Muscular layer surround the pupil called the iris • Color of iris depends on the number and size of melanin pigment • Intrinsic muscles – Sphincter papillae (constricts pupil) – Dilator papillae (dilates pupil) © 2009 Delmar, Cengage Learning Lens and Related Structures • Lens – Crystalline structure located behind the iris and pupil • Ciliary body • Anterior chamber – Aqueous humor • Posterior chamber – Vitreous humor © 2009 Delmar, Cengage Learning Retina • • • • Innermost, or third coat of the eye Images focus on the retina Optic nerve Cerebral cortex (occipital lobe) © 2009 Delmar, Cengage Learning Retina • Rods and cones • Macula lutea and fovea centralis • Optic nerve or blind spot © 2009 Delmar, Cengage Learning Pathway of Vision • • • • • Images in the light Cornea Pupil Lens Retina © 2009 Delmar, Cengage Learning Pathway of Vision • • • • • Rods and cones Optic nerve Optic chiasma Optic tracts Occipital lobe of the brain for interpretation © 2009 Delmar, Cengage Learning Animation – How We See Click Here to play Vision animation © 2009 Delmar, Cengage Learning Eye Disorders • • • • Conjunctivitis Glaucoma Cataracts Macular degeneration © 2009 Delmar, Cengage Learning Eye Disorders • Detached retina • Diabetic retinopathy • Sty (hordeolum) © 2009 Delmar, Cengage Learning Eye Surgery • Cataract surgery – Phacoemulsification – Extracapsular extraction • Detached retina surgery – – – – Laser surgery and cryotherapy Pneumatic retinopexy Vitrectomy Scleral buckle © 2009 Delmar, Cengage Learning Eye Surgery • Visual defects • LASIK (laser-assisted in-situ keratomileusis) • PRK (photorefractive keratectomy) © 2009 Delmar, Cengage Learning Eye Injuries • Simple eye irritation • Corneal abrasions and scarring • Chemical or fragment eye irritations © 2009 Delmar, Cengage Learning Eyestrain • • • • Signs and symptoms Most common cause is a computer Dry eyes can also cause eyestrain Prevention © 2009 Delmar, Cengage Learning Vision Defects • • • • • Night blindness Color blindness Presbyopia Hyperopia Myopia © 2009 Delmar, Cengage Learning Vision Defects • • • • Amblyopia Astigmatism Diplopia Strabismus © 2009 Delmar, Cengage Learning Effects of Aging – Eye • • • • Decreased ability to focus on fine detail Compromised accommodation Slower to adjust to changing light conditions Peripheral vision and depth perception decline • Loss of visual acuity © 2009 Delmar, Cengage Learning The Ear • Picks up sound waves and sends these impulses to the auditory center of the brain • Auditory center in temporal area just above ears • Receptor for hearing – Organ of Corti • Involved in equilibrium © 2009 Delmar, Cengage Learning Outer Ear • Pinna • Canal glands • Tympanic membrane © 2009 Delmar, Cengage Learning Middle Ear • Connects to pharynx (throat) via eustachian tube • Hammer (malleus) • Anvil (incus) • Stirrup (stapes) © 2009 Delmar, Cengage Learning Inner Ear • • • • Cochlea Cochlear duct Organ of Corti Three semicircular canals © 2009 Delmar, Cengage Learning Pathway of Hearing • • • • • Sound waves Pinna Auditory canal Tympanic membrane Ear ossicles © 2009 Delmar, Cengage Learning Pathway of Hearing • Cochlea receptors • Cochlear nerve • Temporal lobe of the brain for interpretation © 2009 Delmar, Cengage Learning Animation – How We Hear Click Here to play Hearing animation © 2009 Delmar, Cengage Learning Pathway of Equilibrium • Movement of head • Stimulates equilibrium receptors in the semicircular and vestibule areas of the inner ear • Vestibular nerve • Cerebellum of the brain for interpretation © 2009 Delmar, Cengage Learning Loud Noise and Hearing Loss • • • • Hearing is both sensitive and fragile Damage done by loud noises Sound measured in decibels Prevention of damage © 2009 Delmar, Cengage Learning Ear Disorders • • • • • Otitis media Otosclerosis Tinnitus Presbycusis Meniere’s disease © 2009 Delmar, Cengage Learning Types of Hearing Loss • Conductive hearing loss • Sensorineural damage © 2009 Delmar, Cengage Learning Effects of Aging – Hearing • Tympanic membrane becomes fibrous • Degeneration of ear bones, vestibular structure, cochlea, and organ of Corti • Loss of hearing high-pitched frequencies • Diminished ability to hear consonants • Speech of others sounds garbled © 2009 Delmar, Cengage Learning Hearing Aids • • • • Behind the ear (BTE) In the ear (ITE) Canal aids Body aids © 2009 Delmar, Cengage Learning The Nose • Smell accounts for about 90% of what we think of as taste • Warms and moistens air breathed in • Receptors – Olfactory epithelium and bulbs • Olfactory nerve • Limbic system, thalamus, and frontal cortex © 2009 Delmar, Cengage Learning Disorders of the Nose • Rhinitis • Nasal polyps • Deviated nasal septum © 2009 Delmar, Cengage Learning Effects of Aging – Smell • Decreased in the number of olfactory neurons • Decreased sense of smell affects appetite, social relationships, and detection of warning smells • Senile rhinitis © 2009 Delmar, Cengage Learning The Tongue • • • • Tongue is a mass of muscle tissue Papillae Taste buds for sweet, sour, salty, and bitter Receptors in the taste buds send stimuli through three cranial nerves to the cerebral cortex for interpretation © 2009 Delmar, Cengage Learning Effects of Aging – Tasting • Decrease in taste buds • Increased amounts of salt, sweet, sour, and bitter needed to identify the food • Impact of full upper dentures © 2009 Delmar, Cengage Learning Disorders of the Tongue • • • • • • Traumatic injury Hairiness Discoloration Infection Cancer Burning mouth syndrome © 2009 Delmar, Cengage Learning
