1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition Elaine N. Marieb Chapter 8 Special Senses

2. The Senses Slide 8.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  General senses of touch  Temperature  Pressure  Pain  Special senses  Smell  Taste  Sight  Hearing  Equilibrium

3. The Eye and Vision Slide 8.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  70 percent of all sensory receptors are in the eyes, only see 1/6 th of eye  Each eye has over a million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye

4. Accessory Structures of the Eye Slide 8.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Eyelids  Meets at medial and lateral canthus (crease)  Eyelashes Figure 8.1b

5. Accessory Structures of the Eye Slide 8.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Eyelashes  Meibomian glands - modified sebacious glands produce an oily secretion to lubricate the eye Figure 8.1b

6. Accessory Structures of the Eye Slide 8.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Ciliary glands – modified sweat glands between the eyelashes Figure 8.1b

7. Accessory Structures of the Eye Slide 8.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Conjunctiva  Membrane that lines eyelids  Connects to the surface of eye  Secretes mucus to lubricate eye  When inflamed, conjunctivitis

8. Accessory Structures of the Eye Slide 8.4b  Lacrimal apparatus  Glands, ducts, (eye), canals, sac, nasolacrimal duct  Tears: antibodies, lysozymes, stress? Figure 8.1a

9. Extrinsic Eye Muscles Slide 8.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscles attach to the outer surface of the eye  Produce eye movements Figure 8.2

10. Structure of the Eye Slide 8.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The wall is composed of three tunics  Sclera & Cornea fibrous outside layer  Choroid – middle layer  Sensory tunic – (retina) inside layer Figure 8.3a

11. The Fibrous Tunic Slide 8.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”  Cornea  Transparent, central anterior portion  Allows for light to pass through  Repairs itself easily  The only human tissue that can be transplanted without fear of rejection

12. Choroid Layer Slide 8.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Blood-rich, nutritive tunic  Pigment prevents light from scattering  Modified interiorly into two structures  Ciliary body – smooth muscle  Iris  Pigmented layer that gives eye color  Pupil – rounded opening in the iris

13. Sensory Tunic (Retina)  Contains receptor cells (photoreceptors)  Rods- Most are found towards the edges of the retina  Allow dim light vision and peripheral vision  Perception in gray tones  Cones – 3 types detect different colors  Densest in the center of the retina  Fovea centralis – area of the retina with only cones  Lack of one type = color blindness  Signals pass from photoreceptors; leave the retina toward the brain through the optic nerve  No photoreceptor cells are at the optic disk, or blind spot

14. Neurons of the Retina Slide 8.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.4

15. Lens  Biconvex crystal-like structure  Held in place by a suspensory ligament attached to the ciliary body

16. Internal Eye Chamber Fluids  Aqueous humor in Anterior Segment  Watery fluid found in chamber between lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure  Provides nutrients for the lens and cornea  Reabsorbed into venous blood  Blocked drainage = inc pressure = glaucoma

17. Internal Eye Chamber Fluids Slide 8.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vitreous humor in Posterior Segment  Gel-like substance behind lens  Keeps the eye from collapsing  Lasts a lifetime and is not replaced

18. Lens Accommodation  Light must be focused to point on retina for optimal vision  The eye is set for distance vision (over 20 ft away)  The lens must change shape to focus for closer objects

19. Correcting the Eye Correct Focus = emmetropia Nearsightedness = myopia –Focus of light in front of retina –Eyeball too long or lens too strong –Distant objects are blurry Farsightedness = hyperopia –Focus of light beyond the retina –Short eyeball or lazy lens –Near objects are blurry.

20. Emmetropia

22. Hyperopia

23. Astigmatism Unequal curvatures in cornea & lens

24. The Ear Slide 8.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Houses two senses  Hearing  Equilibrium (balance)  Receptors are mechanoreceptors

25. Anatomy of the Ear  The ear is divided into 3 areas  Outer (external) ear  Middle ear  Inner ear

26. The External Ear  Involved in hearing only  Structures of external ear  Pinna (auricle)  External auditory canal

27. The External Auditory Canal Slide 8.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Narrow chamber in the temporal bone  Lined with skin  Ceruminous (wax) glands present  Ends at the tympanic membrane (ear drum)

28. The Middle Ear or Tympanic Cavity Slide 8.24a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Air-filled cavity within temporal bone  Only involved in sense of hearing

29. The Middle Ear or Tympanic Cavity  2 tubes are associated with the ear  opening from auditory canal is covered by the tympanic membrane  auditory tube (Eustachian tube) connecting middle ear with throat  equalizing pressure during yawning or swallowing  otherwise collapsed

30. Bones of the Tympanic Cavity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Three bones span cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip) Figure 8.12

31. Bones of the Tympanic Cavity Slide 8.25b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vibrations from eardrum move malleus  These bones transfer sound to inner ear Figure 8.12

32. Inner Ear or Bony Labyrinth Slide 8.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Includes sense organs for hearing and balance  Filled with perilymph (liquid) Figure 8.12

33. Inner Ear or Bony Labrynth  Maze of bony chambers within temporal bone  Cochlea  Vestibule  Semicircular canals

34. Organs of Hearing  Organ of Corti  Located within cochlea  Receptors = hair cells on basilar membrane  Gel-like tactorial membrane is capable of bending hair cells  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe

35. Organs of Hearing Slide 8.27b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.13

36. Mechanisms of Hearing Slide 8.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vibrations from sound waves move tectorial membrane  Hair cells are bent by the membrane  An action potential starts in the cochlear nerve  Continued stimulation can lead to adaptation

37. Mechanisms of Hearing Slide 8.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14

38. Mechanisms of Hearing Slide 8.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14 Uncoiled cochlea: sound waves below level of hearing travel w/o exciting hair cells 1- Higher pitched sounds make pressure waves that penetrate through cochlea and reach scala tympani 2- Membrane vibrates and response to frequencies of sound, stimulating hair cells

39. Organs of Equilibrium Slide 8.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Receptor cells are in two structures  Vestibule  Semicircular canals Figure 8.16a, b

40. Organs of Equilibrium Slide 8.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Equilibrium has two functional parts  Static equilibrium – sense of gravity at rest  Dynamic equilibrium – angular and rotary head movements Figure 8.16a, b

41. Static Equilibrium - Rest Slide 8.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Maculae – receptors in the vestibule  Report on position of head  Send information via vestibular nerve  Anatomy of the maculae  Hair cells are embedded in otolithic membrane  Otoliths (tiny stones) float in a gel around hair cells  Movements cause otoliths to bend hair cells

42. Function of Maculae Slide 8.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.15

43. Dynamic Equilibrium - Movement Slide 8.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Crista ampullaris – receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers hair cells Figure 8.16c

44. Dynamic Equilibrium Slide 8.33b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Action of angular head movements  The cupula stimulates hair cells  An impulse is sent via vestibular nerve to cerebellum Figure 8.16c

45. Chemical Senses Taste and Smell Slide 8.34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Both senses use chemoreceptors  Both stimulated by chemicals in solution  Taste has 4 types of receptors  Smell can differentiate a large range of chemicals  Both senses complement each other and respond to many of same stimuli!

46. Olfaction – The Sense of Smell  Olfactory receptors are in roof of the nasal cavity  Neurons with long cilia  Chemicals must be dissolved in mucus for detection

47. Olfaction – The Sense of Smell  Impulses are transmitted via olfactory nerve  Interpretation of smells made in cortex

48. The Sense of Taste Slide 8.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Taste buds house the receptor organs  Location of taste buds  Most are on the tongue  Soft palate  Cheeks Figure 8.18a, b

49. The Tongue and Taste  The tongue is covered w/ projections,or papillae  Filiform papillae sharp w/ no taste buds  Fungifiorm papillae rounded w/ taste buds  Circumvallate papillae large w/ taste buds

50. The Tongue and Taste  Taste buds are found on the sides of papillae

51. Structure of Taste Buds  Gustatory cells are the receptors  Have gustatory hairs (long microvilli)  Hairs stimulated by chemicals dissolved in saliva

52. Structure of Taste Buds  Impulses carried to gustatory complex by several cranial nerves b/c taste buds found in different areas Facial, Glossopharyngeal & Vagus nerves

53. Taste Sensations Slide 8.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sweet receptors  Sugars  Saccharine  Some amino acids  indicates energy-rich nutrients

54. Taste Sensations Slide 8.41  Sour receptors  Acids

55. Taste Sensations  Bitter receptors allows sensing diverse natural toxins

56. Taste Sensations  Salty receptors allows modulating diet for electrolyte balance

57. Developmental Aspects of All Special Senses  Formed early in embryonic development  Eyes are outgrowths of the brain  All special senses are functional at birth

58. Short taste intro Short taste intro Relationship between smell and taste Relationship between smell and tasteRelationship between smell and tasteRelationship between smell and taste