1. SPECIAL SENSES

2. Senses
General Senses include temperature, pain, touch, pressure, vibration, and proprioception.
Special Senses include olfaction, gustation, equilibrium, vision, and hearing.

3. Types of Receptors
Mechanoreceptors—stretching, touch, pressure in autonomic NS structures (barorecpetors) and body position (proprioceptors)
Chemoreceptors--chemical—gustation, olfaction, and autonomic NS chemicals
Nociceptors--pain
Thermoreceptors--temperature
Photoreceptors--light--70% of all receptors

4. Taste (Gustation) Closely associated with smell
Gustatory Organs (Taste Buds)
Located along the surface in elevations called Papillae (10,000 or more)

5. Taste Buds Respond to dissolved chemicals 6 types of taste sensations
Sweet
Sour
Bitter
Salty
Umami
Water

6. Smell (Olfaction) Detect 50 or more specific scents
Olfactory organs in the upper wall of the nasal cavity
Bipolar neurons – Receptor cells –Olfactory hair cells
Mucous membranes trap particles

7. Smell (Olfaction) LowThreshold: amount needed for detection
Adaptation: time for decrease in sensitivity
First second or so about 50% gone
FYI: Usually in one minute even strong scents are no longer smelled

8. Sight (Vision) Most complex of special senses
over 70% of the sensory receptors in the body are photoreceptors for sight
Includes eye, and accessory structures

9. Accessory structures of the eye
Eyelid, eyebrow, eyelashes = protect
Exocrine glands
Conjunctiva=mucous membrane of the eyelid and eye
Helps moisten and lubricate the eyeball

10. Accessory Structures of the Eye
Lacrimal apparatus (lacrimal glands, lacrimal canals, nasolacrimal duct)
Produces tears to keep eye moist
Fights infection (enzymes)
Drains through the nasal cavity

11. Accessory structures of the eye
Extrinsic muscle of the eye
6 muscles that move eyes

12. Structure of the Eye
The wall consists of three layers of tissue or tunics
Fibrous Tunic - outer layer
Vascular Tunic - middle layer
Nervous Tunic - inner layer

13. Fibrous Tunic Outermost layer Sclera forms most of the fibrous tunic
the white of the eye

14. Fibrous layer of the Eye (continued)
Cornea- anterior transparent portion of the eye
Refracts light
Bulges outward due to aqueous humor (anterior cavity)
Most common transplant

15. Vascular Tunic Blood supply Choroid-thin posterior portion
Thin dark brown membrane
Ciliary body-thick anterior portion, attaches to lens with ligaments
Iris-colored portion

16. Pupil dilation and constriction
Iris = made of circular and radial smooth muscles
Pupil= hole in iris changes size according to light

17. Vascular Tunic (cont) Lens Viterous Humor (fluid body)
changes shape for
close-up or long range
lens accommodation
Ligaments attached to ciliary body
Viterous Humor (fluid body)
looks like clear jelly
Holds retina in place

18. Nervous Tunic The inner layer of the eye
Retina = thin fragile layer of neurons (few mm thick)
Contains photoreceptors (rods and cones) and neurons
Optic Nerve
Transmits images to occipital lobe

19. Rods and Cones--neurons in retina
Elongated dendrites
Black and white and night vision
Cones
Dendrites with tapered ends
Color sensitive
Sharpens vision

20. Other Structures of the Nervous Tunic
Optic Disc - blind spot where the optic nerve exits the retina
Fovea Centralis - an area of the retina containing many cone cells
the area of sharpest vision

21. Visual Pathway

22. Hearing Dependent upon special organs within the ear
The ears are also associated with maintaining equilibrium and balance
Three Regions of the Ear
Outer Ear
Middle Ear
Inner Ear

23. Outer Ear Direct sound waves toward the eardrum
Auricle = the outer portion
Auditory Canal = extends into temporal bone
Cerumen=ear wax-modified sweat glands-protection

24. Middle Ear Air filled space Aka Tympanic Cavity Auditory Ossicles
Amplify sound wave and pass it to the oval window
smallest bones in the body
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)

25. Middle Ear (cont) Eustachian Tube = Middle Ear to the Pharynx (throat)
Pressure equalization
Tympanic Membrane (Eardrum)
Vibrates
Transmits movement to the “oval window”
Opens to the cochlea
Causes fluid to stimulate receptors for hearing

26. The Inner Ear Hearing and equilibrium Cochlea (hearing)
Vestibule (balance)
Semicircular Canals (balance)

27. Cochlea Resembles a snail shell
Contains the Organs of Corti for hearing
Contains perilymph and endolymph (fluids)
Receptor cells that move in response to endolymph motion
FYI: surrounded by bony labyrinth
FYI: Fluids aid in transmission of vibration

28. Hearing Organs--Organs of Corti
Vibrate to endolymph motion
Release neurotransmitters

29. Steps of Hearing 1. Sound waves enter auditory canal
2. Eardrum vibrates
3. Ossicles vibrate and magnify sound
4. Oval window vibrates causes fluids to vibrate
5. Fluids movement causes hair cells to vibrate
6. Vibration –neurotransmitter - auditory nerve - brain

30. Equilibrium (Balance)
Aided by receptor cells in the Inner Ear
Determined by body position and movement of head
Uses sight & neurotransmitters sent by semicircular canals and vestibule

31. Semicircular canals Three loops at right angles
Ampulla at entrance of loops contain cristae
Hair cells in cristae release neurotransmitters
Brain interprets & responds

32. Vestibule Vestibule: chamber between the cochlea & semicircular canals
Contains perilymph and endolymph (bony labyrinth)

33. Vestibule cont Maculae =contain hair-like cells
Otoliths on surface, move
Otoliths respond to gravity

34. DISEASES AND DISORDERS OF THE SPECIAL SENSES

35. Presbyopia Lens looses ability to change shape
Results in farsightedness
Usually caused by age

36. Myopia (near sighted) Caused by eye shape being too long
Causes light to focus in front of retina
Corrected with glasses or contacts

37. Hyperopia (far-sighted)
Caused by eye shape being shorter than normal
Causes light to focus behind the retina
Corrected with glasses or contacts

38. Cataracts Caused by clouding of the lens
Can be replaced with artificial lens

39. Conjunctivitis Caused by an infection of the conjuctiva
More commonly called “pink eye”

40. Strabismus Caused by weak eye muscles
Can be surgically corrected or by patching the good eye to encourage other eye to work properly

41. Glaucoma
Aqueous humor build up puts pressure on the retina resulting in atrophy of optic nerve
Can damage retina if not treated
Eye drops
Surgical incision

42. Macular Degeneration
Section of the retina called the macula (large concentration of blood vessels) is damaged causing tunnel vision until vision is gone

43. Deafness Conductive: caused by blockages in the auditory canal
Caused by middle ear infections
Eardrum damage

44. Sensorineural deafness
Damage to auditory nerves
Cochlear malformation or damaged by infection
Brain damage in temporal lobe

45. Middle Ear Infection (Otitis Media)
Usually involves the eardrum being infected by bacteria or virus
Bacterial treated with antibiotics
Common in children

46. Tinnitis Ringing in the ears
Caused by improper discharge of electrical impulses of the Organs of Corti hair cells

47. Vertigo Caused by otoliths improperly aligning with membranes
Causes dizziness and nausea

48. DISEASES AND DISORDERS OF THE SPECIAL SENSES

49. Presbyopia
Lens loses ability to change shape
Usually caused by age

50. Myopia (near sighted) Caused by eye shape being too long
Causes light to focus in front of retina
Corrected with glasses or contacts

51. Hyperopia (far-sighted)
Caused by eye shape being shorter than normal
Causes light to focus behind the retina
Corrected with glasses or contacts

52. Astigmatisim Caused by corneal malformation
Creates a distorted image on the retina

53. Cataracts Caused by clouding of the lens
Can be replaced with artificial lens

54. Cataract

55. Conjunctivitis Caused by an infection of the conjunctiva
More commonly called “pink eye”

56. Conjunctivitis

57. Glaucoma Aqueous humor build up puts pressure on the retina
Can damage retina if not treated

58. Macular Degeneration Occurs in section of the retina called the macula
damaged causing a dark area that progresses over time

59. Macular Degeneration

60. Strabismus Caused by weak eye muscles
Sometimes referred to as crossed eyes
Can be surgically corrected or by patching the good eye to encourage other eye to work properly

61. Deafness
Two types:
Conductive: caused by blockages in the auditory canal
Can be blocked with ear wax
Can be caused by middle ear infections or
Eardrum damage

62. Sensorineural deafness
Damage to auditory nerves
Cochlear malformation or damaged by infection
Brain damage in temporal lobe

63. Cochlear Implants

64. Middle Ear Infection
Usually involves the eardrum being infected by bacteria or virus
Bacterial treated with antibiotics
Common in children
Called Otis Media

65. Tinnitus
Caused by improper discharge of electrical impulses of the Organs of Corti Hair cells

66. Vertigo Caused by otoliths improperly aligning with membranes
May also be caused by middle ear infection moving into inner ear
Causes dizziness and nausea

67. THE END!