Special senses

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Special senses

  1. 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. 2. The Senses Slide 8.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>General senses of touch </li></ul><ul><ul><li>Temperature </li></ul></ul><ul><ul><li>Pressure </li></ul></ul><ul><ul><li>Pain </li></ul></ul><ul><li>Special senses </li></ul><ul><ul><li>Smell </li></ul></ul><ul><ul><li>Taste </li></ul></ul><ul><ul><li>Sight </li></ul></ul><ul><ul><li>Hearing </li></ul></ul><ul><ul><li>Equilibrium </li></ul></ul>
  3. 3. The Eye and Vision Slide 8.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>70 percent of all sensory receptors are in the eyes, only see 1/6 th of eye </li></ul><ul><li>Each eye has over a million nerve fibers </li></ul><ul><li>Protection for the eye </li></ul><ul><ul><li>Most of the eye is enclosed in a bony orbit </li></ul></ul><ul><ul><li>A cushion of fat surrounds most of the eye </li></ul></ul>
  4. 4. Accessory Structures of the Eye Slide 8.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Eyelids </li></ul><ul><ul><li>Meets at medial and lateral canthus </li></ul></ul><ul><li>Eyelashes </li></ul>Figure 8.1b
  5. 5. Accessory Structures of the Eye Slide 8.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Eyelashes =Meibomian glands modified sebacious glands produce an oily secretion to lubricate the eye </li></ul>Figure 8.1b
  6. 6. Accessory Structures of the Eye Slide 8.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Ciliary glands – modified sweat glands between the eyelashes </li></ul>Figure 8.1b
  7. 7. Accessory Structures of the Eye Slide 8.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Conjunctiva </li></ul><ul><ul><li>Membrane that lines the eyelids </li></ul></ul><ul><ul><li>Connects to the surface of the eye </li></ul></ul><ul><ul><li>Secretes mucus to lubricate the eye </li></ul></ul>
  8. 8. Accessory Structures of the Eye Slide 8.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Lacrimal apparatus </li></ul><ul><ul><li>Glands, ducts, (eye), canals, sac, nasolacrimal duct </li></ul></ul><ul><ul><li>Tears: antibodies, lysozymes, stress? </li></ul></ul>Figure 8.1a
  9. 9. Extrinsic Eye Muscles Slide 8.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscles attach to the outer surface of the eye </li></ul><ul><li>Produce eye movements </li></ul>Figure 8.2
  10. 10. Structure of the Eye Slide 8.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>The wall is composed of three tunics </li></ul><ul><ul><li>Sclera&Cornea fibrous outside layer </li></ul></ul><ul><ul><li>Choroid – middle layer </li></ul></ul><ul><ul><li>Sensory tunic – (retina) inside layer </li></ul></ul>Figure 8.3a
  11. 11. The Fibrous Tunic Slide 8.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Sclera </li></ul><ul><ul><li>White connective tissue layer </li></ul></ul><ul><ul><li>Seen anteriorly as the “white of the eye” </li></ul></ul><ul><li>Cornea </li></ul><ul><ul><li>Transparent, central anterior portion </li></ul></ul><ul><ul><li>Allows for light to pass through </li></ul></ul><ul><ul><li>Repairs itself easily </li></ul></ul><ul><ul><li>The only human tissue that can be transplanted without fear of rejection </li></ul></ul>
  12. 12. Choroid Layer Slide 8.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Blood-rich nutritive tunic </li></ul><ul><li>Pigment prevents light from scattering </li></ul><ul><li>Modified interiorly into two structures </li></ul><ul><ul><li>Cilliary body – smooth muscle </li></ul></ul><ul><ul><li>Iris </li></ul></ul><ul><ul><ul><li>Pigmented layer that gives eye color </li></ul></ul></ul><ul><ul><ul><li>Pupil – rounded opening in the iris </li></ul></ul></ul>
  13. 13. Sensory Tunic (Retina) Slide 8.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Contains receptor cells (photoreceptors) </li></ul><ul><ul><li>Rods </li></ul></ul><ul><ul><li>Cones </li></ul></ul><ul><li>Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve </li></ul>
  14. 14. Neurons of the Retina Slide 8.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.4
  15. 15. Neurons of the Retina and Vision Slide 8.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Rods </li></ul><ul><ul><li>Most are found towards the edges of the retina </li></ul></ul><ul><ul><li>Allow dim light vision and peripheral vision </li></ul></ul><ul><ul><li>Perception is all in gray tones </li></ul></ul>
  16. 16. Neurons of the Retina and Vision Slide 8.12b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Cones – 3 types detect different colors </li></ul><ul><ul><li>Densest in the center of the retina </li></ul></ul><ul><ul><li>Fovea centralis – area of the retina with only cones </li></ul></ul><ul><ul><li>Lack of one type = color blindness </li></ul></ul><ul><li>No photoreceptor cells are at the optic disk, or blind spot </li></ul>
  17. 17. Lens Slide 8.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Biconvex crystal-like structure </li></ul><ul><li>Held in place by a suspensory ligament attached to the ciliary body </li></ul>Figure 8.3a
  18. 18. Internal Eye Chamber Fluids Slide 8.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Aqueous humor in Anterior Segment </li></ul><ul><ul><li>Watery fluid found in chamber between the lens and cornea </li></ul></ul><ul><ul><li>Similar to blood plasma </li></ul></ul><ul><ul><li>Helps maintain intraocular pressure </li></ul></ul><ul><ul><li>Provides nutrients for the lens and cornea </li></ul></ul><ul><ul><li>Reabsorbed into venous blood </li></ul></ul><ul><ul><li>Blocked drainage = glaucoma </li></ul></ul>
  19. 19. Internal Eye Chamber Fluids Slide 8.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Vitreous humor in Posterior Segment </li></ul><ul><ul><li>Gel-like substance behind the lens </li></ul></ul><ul><ul><li>Keeps the eye from collapsing </li></ul></ul><ul><ul><li>Lasts a lifetime and is not replaced </li></ul></ul>
  20. 20. Lens Accommodation Slide 8.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Light must be focused to a point on the retina for optimal vision </li></ul><ul><li>The eye is set for distance vision (over 20 ft away) </li></ul><ul><li>The lens must change shape to focus for closer objects </li></ul>Figure 8.9
  21. 21. Correcting the Eye <ul><li>Correct Focus = emmetropia </li></ul><ul><li>Nearsightedness = myopia </li></ul><ul><ul><li>Focus of light in front of retina </li></ul></ul><ul><ul><li>Eyeball too long or lens too strong </li></ul></ul><ul><ul><li>Distant objects are blurry </li></ul></ul><ul><li>Farsightedness = hyperopia </li></ul><ul><ul><li>Focus of light beyond the retina </li></ul></ul><ul><ul><li>Short eyeball or lazy lens </li></ul></ul><ul><ul><li>Near objects are blurry. </li></ul></ul>
  22. 22. Emmetropia
  23. 24. Hyperopia
  24. 25. Astigmatism <ul><li>Unequal curvatures in cornea & lens </li></ul>
  25. 26. The Ear Slide 8.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Houses two senses </li></ul><ul><ul><li>Hearing </li></ul></ul><ul><ul><li>Equilibrium (balance) </li></ul></ul><ul><li>Receptors are mechanoreceptors </li></ul>
  26. 27. Anatomy of the Ear Slide 8.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>The ear is divided into three areas </li></ul><ul><ul><li>Outer (external) ear </li></ul></ul><ul><ul><li>Middle ear </li></ul></ul><ul><ul><li>Inner ear </li></ul></ul>Figure 8.12
  27. 28. The External Ear Slide 8.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Involved in hearing only </li></ul><ul><li>Structures of the external ear </li></ul><ul><ul><li>Pinna (auricle) </li></ul></ul><ul><ul><li>External auditory canal </li></ul></ul>Figure 8.12
  28. 29. The External Auditory Canal Slide 8.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Narrow chamber in the temporal bone </li></ul><ul><li>Lined with skin </li></ul><ul><li>Ceruminous (wax) glands are present </li></ul><ul><li>Ends at the tympanic membrane </li></ul>
  29. 30. The Middle Ear or Tympanic Cavity Slide 8.24a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Air-filled cavity within the temporal bone </li></ul><ul><li>Only involved in the sense of hearing </li></ul>
  30. 31. The Middle Ear or Tympanic Cavity Slide 8.24b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Two tubes are associated with the inner ear </li></ul><ul><ul><li>The opening from the auditory canal is covered by the tympanic membrane </li></ul></ul><ul><ul><li>The auditory tube connecting the middle ear with the throat </li></ul></ul><ul><ul><ul><li>Allows for equalizing pressure during yawning or swallowing </li></ul></ul></ul><ul><ul><ul><li>This tube is otherwise collapsed </li></ul></ul></ul>
  31. 32. Bones of the Tympanic Cavity Slide 8.25a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Three bones span the cavity </li></ul><ul><ul><li>Malleus (hammer) </li></ul></ul><ul><ul><li>Incus (anvil) </li></ul></ul><ul><ul><li>Stapes (stirrip) </li></ul></ul>Figure 8.12
  32. 33. Bones of the Tympanic Cavity Slide 8.25b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Vibrations from eardrum move the malleus </li></ul><ul><li>These bones transfer sound to the inner ear </li></ul>Figure 8.12
  33. 34. Inner Ear or Bony Labyrinth Slide 8.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Includes sense organs for hearing and balance </li></ul><ul><li>Filled with perilymph </li></ul>Figure 8.12
  34. 35. Inner Ear or Bony Labrynth Slide 8.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>A maze of bony chambers within the temporal bone </li></ul><ul><ul><li>Cochlea </li></ul></ul><ul><ul><li>Vestibule </li></ul></ul><ul><ul><li>Semicircular canals </li></ul></ul>Figure 8.12
  35. 36. Organs of Hearing Slide 8.27a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Organ of Corti </li></ul><ul><ul><li>Located within the cochlea </li></ul></ul><ul><ul><li>Receptors = hair cells on the basilar membrane </li></ul></ul><ul><ul><li>Gel-like tectorial membrane is capable of bending hair cells </li></ul></ul><ul><ul><li>Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe </li></ul></ul>
  36. 37. Organs of Hearing Slide 8.27b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.13
  37. 38. Mechanisms of Hearing Slide 8.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Vibrations from sound waves move tectorial membrane </li></ul><ul><li>Hair cells are bent by the membrane </li></ul><ul><li>An action potential starts in the cochlear nerve </li></ul><ul><li>Continued stimulation can lead to adaptation </li></ul>
  38. 39. Mechanisms of Hearing Slide 8.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14
  39. 40. Organs of Equilibrium Slide 8.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Receptor cells are in two structures </li></ul><ul><ul><li>Vestibule </li></ul></ul><ul><ul><li>Semicircular canals </li></ul></ul>Figure 8.16a, b
  40. 41. Organs of Equilibrium Slide 8.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Equilibrium has two functional parts </li></ul><ul><ul><li>Static equilibrium – sense of gravity at rest </li></ul></ul><ul><ul><li>Dynamic equilibrium – angular and rotary head movements </li></ul></ul>Figure 8.16a, b
  41. 42. Static Equilibrium - Rest Slide 8.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Maculae – receptors in the vestibule </li></ul><ul><ul><li>Report on the position of the head </li></ul></ul><ul><ul><li>Send information via the vestibular nerve </li></ul></ul><ul><li>Anatomy of the maculae </li></ul><ul><ul><li>Hair cells are embedded in the otolithic membrane </li></ul></ul><ul><ul><li>Otoliths (tiny stones) float in a gel around the hair cells </li></ul></ul><ul><ul><li>Movements cause otoliths to bend the hair cells </li></ul></ul>
  42. 43. Function of Maculae Slide 8.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.15
  43. 44. Dynamic Equilibrium - Movement Slide 8.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Crista ampullaris – receptors in the semicircular canals </li></ul><ul><ul><li>Tuft of hair cells </li></ul></ul><ul><ul><li>Cupula (gelatinous cap) covers the hair cells </li></ul></ul>Figure 8.16c
  44. 45. Dynamic Equilibrium Slide 8.33b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Action of angular head movements </li></ul><ul><ul><li>The cupula stimulates the hair cells </li></ul></ul><ul><ul><li>An impulse is sent via the vestibular nerve to the cerebellum </li></ul></ul>Figure 8.16c
  45. 46. Chemical Senses – Taste and Smell Slide 8.34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Both senses use chemoreceptors </li></ul><ul><ul><li>Stimulated by chemicals in solution </li></ul></ul><ul><ul><li>Taste has four types of receptors </li></ul></ul><ul><ul><li>Smell can differentiate a large range of chemicals </li></ul></ul><ul><li>Both senses complement each other and respond to many of the same stimuli </li></ul>
  46. 47. Olfaction – The Sense of Smell Slide 8.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Olfactory receptors are in the roof of the nasal cavity </li></ul><ul><ul><li>Neurons with long cilia </li></ul></ul><ul><ul><li>Chemicals must be dissolved in mucus for detection </li></ul></ul><ul><li>Impulses are transmitted via the olfactory nerve </li></ul><ul><li>Interpretation of smells is made in the cortex </li></ul>
  47. 48. Olfactory Epithelium Slide 8.36 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.17
  48. 49. The Sense of Taste Slide 8.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Taste buds house the receptor organs </li></ul><ul><li>Location of taste buds </li></ul><ul><ul><li>Most are on the tongue </li></ul></ul><ul><ul><li>Soft palate </li></ul></ul><ul><ul><li>Cheeks </li></ul></ul>Figure 8.18a, b
  49. 50. The Tongue and Taste Slide 8.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>The tongue is covered with projections called papillae </li></ul><ul><ul><li>Filiform papillae – sharp with no taste buds </li></ul></ul><ul><ul><li>Fungifiorm papillae – rounded with taste buds </li></ul></ul><ul><ul><li>Circumvallate papillae – large papillae with taste buds </li></ul></ul><ul><li>Taste buds are found on the sides of papillae </li></ul>
  50. 51. Structure of Taste Buds Slide 8.39a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Gustatory cells are the receptors </li></ul><ul><ul><li>Have gustatory hairs (long microvilli) </li></ul></ul><ul><ul><li>Hairs are stimulated by chemicals dissolved in saliva </li></ul></ul>
  51. 52. Structure of Taste Buds Slide 8.39b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas </li></ul><ul><ul><li>Facial nerve </li></ul></ul><ul><ul><li>Glossopharyngeal nerve </li></ul></ul><ul><ul><li>Vagus nerve </li></ul></ul>
  52. 53. Anatomy of Taste Buds Slide 8.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.18
  53. 54. Taste Sensations Slide 8.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Sweet receptors </li></ul><ul><ul><li>Sugars </li></ul></ul><ul><ul><li>Saccharine </li></ul></ul><ul><ul><li>Some amino acids </li></ul></ul><ul><li>Sour receptors </li></ul><ul><ul><li>Acids </li></ul></ul><ul><li>Bitter receptors </li></ul><ul><ul><li>Alkaloids </li></ul></ul><ul><li>Salty receptors </li></ul><ul><ul><li>Metal ions </li></ul></ul>
  54. 55. Developmental Aspects of the Special Senses Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Formed early in embryonic development </li></ul><ul><li>Eyes are outgrowths of the brain </li></ul><ul><li>All special senses are functional at birth </li></ul>

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