© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 10 Special Senses

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. General Sensory Receptors Stimulated by changes in the environment Generalized in body –Touch, pain, temperature, and pressure (proprioceptors)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Special Senses Touch Vision Hearing Smell Taste

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Eye Tender sphere about 1 inch (2.5 cm) in diameter Protected by orbital socket, eyebrows, eyelids, and eyelashes Lacrimal duct and glands

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Eye Oil glands Conjunctiva Stereoscopic vision The wall of the eye has three layers –Sclera –Choroid –Retina

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure 10-1 External view of the eye

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure 10-2 The layers of the eyeball are made up of the sclera, choroid, and retina.

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Sclera Outer layer of the eye that is the white of the eye Fibrous capsule maintains shape and protects Extrinsic muscles

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Extrinsic Muscles Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure 10-4 Internal view of the eye

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Choroid Coat and the Iris Muscular layer surrounding the pupil called the iris Color of the iris depends on the number and size of melanin pigment Intrinsic muscles –Sphincter papillae (constricts pupil) –Dilator papillae (dilates pupil)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Lens and Related Structures Lens –Crystalline structure located behind the iris and pupil –Focus images on the retina Ciliary body Anterior chamber –Aqueous humor Posterior chamber –Vitreous humor

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Retina (1 of 2) Innermost, or third coat of the eye Images focus on the retina Optic nerve Cerebral cortex (occipital lobe)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Retina (2 of 2) Rods and cones (color vision) Macula lutea (yellow disc) and fovea centralis (contains the cones) Optic nerve or blind spot

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Pathway of Vision (1 of 2) Images in the light Cornea Pupil Lens Retina

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Pathway of Vision (2 of 2) Rods and cones Optic nerve Optic chiasma Optic tracts Occipital lobe of the brain for interpretation

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure 10-8 Pathway of vision: Images in light→cornea→pupil→lens→retina→optic nerve→occipital lobe (cerebrum)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eye Disorders (1 of 2) Conjunctivitis Glaucoma Cataracts Macular degeneration

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eye Disorders (2 of 2) Detached retina Diabetic retinopathy Sty (hordeolum)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eye Surgery (1 of 2) Cataract surgery –Phacoemulsification –Extracapsular extraction Detached retina surgery –Laser surgery and cryotherapy –Pneumatic retinopexy –Vitrectomy –Scleral buckle

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eye Surgery (2 of 2) Visual defects LASIK (laser-assisted in-situ keratomileusis) PRK (photorefractive keratectomy)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eye Injuries Simple eye irritation Corneal abrasions and scarring Chemical or fragment eye irritations

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Eyestrain Signs and symptoms Most common cause is a computer Dry eyes can also cause eyestrain Prevention

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Vision Defects (1 of 2) Night blindness Color blindness Presbyopia Hyperopia (farsighted) Myopia (nearsighted)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Vision Defects (2 of 2) Amblyopia Astigmatism Diplopia Strabismus

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Effects of Aging on Vision 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

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Ear Picks up sound waves and sends these impulses to the auditory center of the brain Auditory center in temporal area just above the ears Receptor for hearing –Organ of Corti Involved in equilibrium

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure The ear and its structures

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Outer Ear Auricle Auditory canal glands secrete cerumen Tympanic membrane (ear drum)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Middle Ear Connects to pharynx (throat) via eustachian tube, equalizes the air pressure Hammer (malleus) Anvil (incus) Stirrup (stapes)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Inner Ear Labyrinth Oval window Cochlea Cochlear duct Organ of Corti Three semicircular canals

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Pathway of Hearing (1 of 2) Sound waves Auricle Auditory canal Tympanic membrane Ear ossicles

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Pathway of Hearing (2 of 2) Cochlea receptors Cochlear nerve Temporal lobe of the brain for interpretation

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure Pathway of hearing: sound waves → external ear → external auditory canal → eardrum → ear ossicles → cochlea → auditory nerve → temporal lobe (cerebrum)

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Loud Noise and Hearing Loss Hearing is both sensitive and fragile Damage to the hair cells in the organ of Corti done by repeated exposure to loud noises Sound measured in decibels Prevention of damage

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Figure A decibel scale of frequently heard sounds from lowest to highest

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Ear Disorders Otitis media –Myringotomy (ear tubes) Otosclerosis Tinnitus Presbycusis Meniere’s disease

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Types of Hearing Loss Conductive hearing loss –Sounds are blocked by ear wax, infection or fluid in the middle ear Sensorineural damage –Damage to the inner ear or auditory nerve

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Effects of Aging on 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 Changes balance and equlibrium

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Hearing Aids Behind the ear (BTE) In the ear (ITE) Canal aids Body aids

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Nose Smell accounts for about 90% of what we think of as taste Can detect 10,000 different smells Warms and moistens air breathed in Receptors –Olfactory epithelium and bulbs Olfactory nerve Limbic system, thalamus, and frontal cortex

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Disorders of the Nose Rhinitis Nasal polyps Deviated nasal septum

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Effects of Aging on Smell Decrease in the number of olfactory neurons Decreased sense of smell affects appetite, social relationships, and detection of warning smells Senile rhinitis

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Tongue The tongue is a mass of muscle tissue Papillae Taste buds for sweet, sour, salty, bitter, and umami (savory) Receptors in the taste buds send stimuli through three cranial nerves to the cerebral cortex for interpretation

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Effects of Aging on Taste Decrease in number of taste buds May be unlikely to detect spoiled food Impact of full upper dentures

© 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Disorders of the Tongue Traumatic injury Hairiness Discoloration Infection Cancer Burning mouth syndrome