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
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
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. Click Here to play Vision animation
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 Detached retina 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. Click Here to play Hearing animation
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