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Chapter 10

Chapter 10. Special Senses. Special Senses. Touch Vision Hearing Smell Taste . Sensory Receptors. Stimulated by changes in the environment Generalized in body Touch, pain, temperature and pressure (proprioceptors). Sensory Receptors. Specific receptors Taste buds of the tongue

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Chapter 10

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  1. Chapter 10 Special Senses

  2. Special Senses • Touch • Vision • Hearing • Smell • Taste

  3. Sensory Receptors • Stimulated by changes in the environment • Generalized in body • Touch, pain, temperature and pressure (proprioceptors)

  4. 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)

  5. The Eye • Tender sphere about 1 inch (2.5 cm) in diameter • Protected by orbital socket, eyebrows, eyelids, and eyelashes • Lacrimal duct and glands

  6. The Eye • Oil glands • Conjunctiva • Stereoscopic vision • The wall of the eye has three layers • Sclera • Choroid • Retina

  7. The Eye

  8. Sclera • Outer layer of the eye which is the white of the eye • Fibrous capsule maintains shape and protects • Extrinsic muscles

  9. Extrinsic Muscles • Superior rectus • Inferior rectus • Lateral rectus • Medial rectus • Superior rectus • Inferior oblique

  10. 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

  11. 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

  12. 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)

  13. Lens and Related Structures • Lens • Crystalline structure located behind the iris and pupil • Ciliary body • Anterior chamber • Aqueous humor • Posterior chamber • Vitreous humor

  14. Retina • Innermost, or third coat of the eye • Images focus on the retina • Optic nerve • Cerebral cortex (occipital lobe)

  15. Retina • Rods and cones • Macula lutea and fovea centralis • Optic nerve or blind spot

  16. Pathway of Vision • Images in the light • Cornea • Pupil • Lens • Retina

  17. Pathway of Vision • Rods and cones • Optic nerve • Optic chiasma • Optic tracts • Occipital lobe of the brain for interpretation

  18. Animation – How We See Click Here to play Vision animation

  19. Eye Disorders • Conjunctivitis • Glaucoma • Cataracts • Macular degeneration

  20. Eye Disorders • Detached retina • Diabetic retinopathy • Sty (hordeolum)

  21. Eye Surgery • Cataract surgery • Phacoemulsification • Extracapsular extraction • Detached retina surgery • Laser surgery and cryotherapy • Pneumatic retinopexy • Vitrectomy • Scleral buckle

  22. Eye Surgery • Visual defects • LASIK (laser-assisted in-situ keratomileusis) • PRK (photorefractive keratectomy)

  23. Eye Injuries • Simple eye irritation • Corneal abrasions and scarring • Chemical or fragment eye irritations

  24. Eyestrain • Signs and symptoms • Most common cause is a computer • Dry eyes can also cause eyestrain • Prevention

  25. Vision Defects • Night blindness • Color blindness • Presbyopia • Hyperopia • Myopia

  26. Vision Defects • Amblyopia • Astigmatism • Diplopia • Strabismus

  27. 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

  28. 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

  29. Outer Ear • Pinna • Canal glands • Tympanic membrane

  30. Middle Ear • Connects to pharynx (throat) via eustachian tube • Hammer (malleus) • Anvil (incus) • Stirrup (stapes)

  31. Inner Ear • Cochlea • Cochlear duct • Organ of Corti • Three semicircular canals

  32. Pathway of Hearing • Sound waves • Pinna • Auditory canal • Tympanic membrane • Ear ossicles

  33. Pathway of Hearing • Cochlea receptors • Cochlear nerve • Temporal lobe of the brain for interpretation

  34. Animation – How We Hear Click Here to play Hearing animation

  35. 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

  36. Loud Noise and Hearing Loss • Hearing is both sensitive and fragile • Damage done by loud noises • Sound measured in decibels • Prevention of damage

  37. Ear Disorders • Otitis media • Otosclerosis • Tinnitus • Presbycusis • Meniere’s disease

  38. Types of Hearing Loss • Conductive hearing loss • Sensorineural damage

  39. 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

  40. Hearing Aids • Behind the ear (BTE) • In the ear (ITE) • Canal aids • Body aids

  41. 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

  42. Disorders of the Nose • Rhinitis • Nasal polyps • Deviated nasal septum

  43. 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

  44. 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

  45. 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

  46. Disorders of the Tongue • Traumatic injury • Hairiness • Discoloration • Infection • Cancer • Burning mouth syndrome

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