1. Chapter 17: The Special Senses
Muse Bio 2440 w12
Lecture #6 5/24/12

2. Comparison of General and Special Senses
General Senses
Special Senses
Include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations.
Scattered throughout the body.
Simple structures.
Include smell, taste, vision, hearing and equilibrium.
Concentrated in specific locations in the head.
Anatomically distinct structures.
Complex neural pathway.

3. Olfaction: Sense of Smell
Olfactory epithelium contains million receptors.
Olfactory receptor- a bipolar neuron with cilia called olfactory hairs.
- Respond to chemical stimulation of an odorant molecule.
Supporting cells- provide support and nourishment.
Basal cells- replace olfactory receptors.

4. Olfactory Epithelium and Olfactory Receptors

5. Olfactory Epithelium and Olfactory Receptors continued…

6. Smell (Olfaction) Olfactory Pathways
Arriving information reaches information centers without first synapsing in thalamus

7. Physiology of Olfaction
Can detect about 10,000 different odors.
Odorant binds to the receptor of an olfactory hair→ G-protein activation→ activation of adenylate cyclase→ production of cAMP→ opening of Na+ channels→ inflow of Na+ →generator potential→ nerve impulse through olfactory nerves→ olfactory bulbs→ olfactory tract→ primary olfactory area of the cerebral cortex.

8. Olfactory transduction

9. Summary of sense of smell
Odorant molecule binds one of million receptors.
Conformational change in receptor interacts with G protein
G protein activates adenylate cyclase to generate cAMP
cAMP opens Na+ channels to initiate depolarization.
Information on number of action potentials decoded by olfactory
bulbs.
Animals have greater numbers of receptors thus better sense of smell
Usually 10,000 times greater.

10. Gustation: Sense of Taste
Taste bud

11. Taste
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12. Taste (Gustation) Gustatory Discrimination Primary taste sensations
Sweet (sugars)
Salty
Sour (acids)
Bitter (alkali)
umami - savory (fat)

13. Taste (Gustation) Gustatory Discrimination
Dissolved chemicals contact taste hairs
Bind to receptor proteins of gustatory cell
Salt and sour receptors
Chemically gated ion channels
Stimulation produces depolarization of cell
Sweet, bitter, and umami stimuli
G proteins: (proteins that bind GTP- secondary messengers)
gustducins

14. Anatomy of Taste Buds and Papillae
Taste bud- made of three types of epithelial cells: supporting cells, gustatory receptor cells and basal cells.
About 50 gustatory cells per taste bud. Each one has a gustatory hair that projects through the taste pore.
Taste buds are found in the papillae.
Three types of papillae: vallate (circumvallate), fungiform and foliate.

15. Physiology of Gustation
Five types of taste: sour, sweet, bitter, salty and umami.
Tastant dissolves in saliva → plasma membrane of gustatory hair→ receptor potential→ nerve impulse via cranial nerves VII, IX and X→ medulla→ thalamus→ primary gustatory area of the cerebral cortex.

16. Gustatory Pathway

17. Neuronal Pathways for Taste
Chorda tympani (part of VII): carry sensations from anterior one-third of tongue (except from circumvallate papillae
Cranial nerve IX and X carry information from posterior one-third tongue, circumvallate papillae, superior pharynx, epiglottis.
Information goes to medulla oblongata where decussation takes place and information projects from there to the thalamus. Then projects to taste area of cortex (extreme inferior end of the postcentral gyrus)
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18. Specialist taste buds map to certain regions of tongue
Maps differ somewhat , but generally

19. Actions of the Major Tastants
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20. Vision or Sight
Visible light: nm.

21. Accessory Structures of the Eye
Eyelids or palpebrae-
Eyelashes and eyebrows-
Extrinsic eye muscles-

22. Accessory Structures of the Eye

23. The Lacrimal Apparatus
Tears from the lacrimal apparatus- lacrimal glands→ excretory lacrimal ducts→ lacrimal puncta→ lacrimal canals→ nasolacrimal sac→ nasolacrimal duct.

24. Anatomy of the Eyeball

25. The Eye
Figure 17–4b The Sectional Anatomy of the Eye.

26. Wall of the Eyeball Three layers: Fibrous tunic- outer layer
Sclera “white” of the eye
Cornea-transparent coat
Vascular tunic or uvea- middle layer
Choroid
Ciliary body consists of ciliary processes and ciliary muscle
Iris
lens (alpha crystalin protein)
Retina- inner layer
Optic disc
Macula lutea- fovea centralis

27. Responses of the Pupil to Light
Pupil is an opening in the center of the iris.
Contraction of the circular muscles of the iris causes constriction of the pupil.
Contraction of the radial muscles causes dilation of the pupil.

28. Interior of the Eyeball
Lens-
lack blood vessels, consists of a capsule with proteins (crystallins) in layers; transparent.
Lens divides the eyeball into two cavities: anterior and posterior.
Anterior cavity- further divided into anterior and posterior chambers. Both are filled with aqueous humor.
Posterior cavity (vitreous chamber)-filled with vitreous body.

29. Cavities of the Eyeball

30. Refraction of Light Rays
Refraction is the bending of light rays.
The cornea and lens refract light rays.
Most refraction done at corneal level -
repair with corneal re-mapping (keratotomy)

31. Accommodation and the Near Point of Vision
Increase in the curvature of the lens for near vision is called accommodation.
Near point of vision is the minimum distance from the eye that an object can be clearly focused.

32. Refraction Abnormalities and their Correction
Nearsightedness (myopia)- close objects seen clearly. Image is focused in front of the retina. Correction- use of concave lens.
Farsightedness (hyperopia)- distant objects seen clearly. Image is focused behind the retina. Correction- use of convex (magnifyer) lens.

33. Most scientists

34. The Eye Most cones in fovea
Figure 17–6c Photograph of the Retina as Seen through the Pupil.

35. Retina
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36. Rods and Cones Cones- three types: red, green and blue.
Named after the shapes of their outer segments.
Rod- (more sensitive to light, but no color )
Cones- three types: red, green and blue.
Outer segment- contains photopigments. Transduction of light energy into receptor potential occurs here.
Inner segment- contains the nucleus, Golgi complex and mitochondria.

37. Structure of Rod and Cone Photoreceptors
Back of eye
Front of eye

38. Photoreceptors
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39. Photopigments
Two parts: opsin (four types, three in the cones and one in the rod) and retinal (light absorbing part).
Rhodopsin- photopigment in rods.
Cone photopigments- three types. (one for each color)
Absorption of light by a photopigment → structural changes.

40. Bleaching and Regeneration of Photopigment

41. Rod disc in outer segment
Colorless products
Disc
membrane
cis-
retinal
opsin
Cis-retinal
binds to opsin
(regeneration)
Isomerization
of retinal
Light
trans-
Retinal
isomerase
converts trans-
to cis-retinal
Trans-retinal
separates
from opsin
(bleaching)
Rhodopsin
molecule
Colored
photopigment
(rhodopsin) 1 2 3 4
Rod disc in outer segment
Colorless products
Disc
membrane
cis-
retinal
opsin
Isomerization
of retinal
Light
trans-
Retinal
isomerase
converts trans-
to cis-retinal
Trans-retinal
separates
from opsin
(bleaching)
Rhodopsin
molecule
Colored
photopigment
(rhodopsin) 1 2 3
Rod disc in outer segment
Disc
membrane
cis-
retinal
opsin
Isomerization
of retinal
Light
trans-
Trans-retinal
separates
from opsin
(bleaching)
Rhodopsin
molecule
Colored
photopigment
(rhodopsin) 1 2
Rod disc in outer segment
Disc
membrane
cis-
retinal
opsin
Isomerization
of retinal
Light
Rhodopsin
molecule
Colored
photopigment
(rhodopsin) 1

42. 15-42 42

43. Bleaching and Regeneration of Photopigment
Isomerization: In darkness, retinal has a bent shape called cis-retinal. Absorption of photon causes straightening of the retinal (trans-retinal).
Bleaching: trans-retinal separates from opsin.
Regeneration: trans-retinal→ cis-retinal.

44. Light and Dark Adaptation
Light adaptation: Dark → light. Faster.
Dark adaptation: Light →dark. Slow.
Cones regenerate rapidly whereas rhodopsin regenerates more slowly.

45. Operation of Rod Photoreceptors

46. Rods Bipolar photoreceptor cells; black and white vision.
Found over most of retina, but not in fovea. More sensitive to light than cones.
Protein rhodopsin changes shape when struck by light; and eventually separates into its two components: opsin and retinal
Retinal can be converted to Vitamin A from which it was originally derived. In absence of light, opsin and retinal recombine to form rhodopsin.
Rods are unusual sensory cells: when not stimulated they are hyperpolarized. Light causes them to depolarize.
Depolarization of rods causes depolarization of bipolar cells causing depolarization of ganglion cells
Light and dark adaptation: adjustment of eyes to changes in light. Happens because of changes in amount of available rhodopsin.
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47. Color Blindness and Night Blindness
Color blindness- inherited inability to distinguish between certain colors.
Result from the absence of one of the three types of cones.
Most common type: red-green color blindness.
Night blindness or Nyctalopia- vitamin A deficiency.

48. Cones Bipolar receptor cells.
Responsible for color vision and visual acuity.
Numerous in fovea and macula lutea; fewer over rest of retina.
As light intensity decreases so does our ability to see color.
Visual pigment is iodopsin: three types that respond to blue, red and green light
Overlap in response to light, thus interpretations of gradation of color possible: several millions
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49. Processing of Visual Input
Receptor potential in rods and cones→ graded potentials in bipolar neurons and horizontal cells→ nerve impulses in ganglion cells→ optic nerve→ optic chiasm→ optic tract→ thalamus→ primary visual area of cerebral cortex in occipital lobe.

50. Visual Pathway

51. 1 2 4 5 3 1 2 3 4 5 6 1 2 4 3 1 2 3 1 2 1 Visual field of left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
tract
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1 2 4 5 3
Visual field of
left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
tract
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1 2 3 4 5 6
Visual field of
left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
tract
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1 2 4 3
Visual field of
left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1 2 3
Visual field of
left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1 2
Visual field of
left eye
Temporal
half
right eye
Nasal
Midbrain
Left eye
retina
Optic
radiations
Left eye and its pathways
Primary visual area of cerebral
cortex (area 17) in occipital lobe
Lateral geniculate nucleus
of the thalamus
Right eye
Right eye and its pathways
Nasal retina 1

52. Neuronal Pathways
15-52 52

53. Anatomy of the Ear Three main regions:
External (outer) ear- auricle or pinna, external auditory canal, and tympanic membrane.
Ceruminous glands-
Middle ear- auditory ossicles: malleus, incus and stapes.
Auditory (eustachian) tube.
Internal (inner) ear- Labyrinth: bony and membranous. Bony labyrinth- perilymph and membranous labyrinth- endolymph. Oval window and round window- membranous regions.

54. Anatomy of the Ear

55. The Middle Ear and the Auditory Ossicles

56. The Internal Ear

57. The Internal Ear
Three parts: the semicircular canals, the vestibule (both contain receptors for equilibrium) and the cochlea (contains receptors for hearing).
Semicircular canals: anterior, posterior and lateral.
Ampulla-
Vestibule consists of two sacs: utricle and saccule.

58. Semicircular Canals, Vestibule and Cochlea

59. Semicircular Canals, Vestibule and Cochlea

60. Sprial organ Tectorial membrane Basilar membrane
Inner phalangeal cells
Outer phalangeal cells
Inner hair cell
Outer hair cells 60

61. Cochlea
Snail-shaped.
Section through the cochlea shows three channels: cochlear duct, scala vestibuli and scala tympani.
Helicotrema
Vestibular membrane
Basilar membrane
Spiral organ or Organ of Corti- hair cells.

62. Physiology of Hearing Audible sound range: 20-20,000 Hz.
Sound waves→ auricle→ external auditory canal→ tympanic membrane→ malleus→ incus→ stapes→ oval window→ perilymph of the scala vestibuli→ vestibular membrane→ endolymph in the cochlear duct→ basilar membrane →hair cells against tectorial membrane → bending of hair cell stereocilia→ receptor potential→ nerve impulse. Sound wave → scala tympani→ round window.
Be able to trace sound thru ear

63. Events in the Stimulation of Auditory Receptors

64. Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4 5 6 7
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4 5 6 7 8
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4 5 6 7 8 9
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4 5 6
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4 5
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1 2 3 4
Scala
vestibuli
Cochlear duct
(contains endolymph)
tympani
Perilymph
Basilar
membrane
Cochlea
Sound waves
Helicotrema
Stapes vibrating
in oval window
Malleus
Incus
External auditory
canal
Tympanic
Secondary tympanic
membrane vibrating
in round window
Auditory tube
Vestibular membrane
Middle ear
Tectorial membrane
Spiral organ
(organ of Corti) 1

65. The Ear end Response map high low
Figure 17–30 Frequency Discrimination.
Response map
high
low

66. Effect of Sound Waves on Points Along the Basilar Membrane
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67. Opening of K+ Channels
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68. The Auditory Pathway

69. Physiology of Equilibrium
Two types of equilibrium:
Static- maintenance of the body position relative to the force of gravity.
Dynamic- maintenance of body position (mainly head) in response to rotational acceleration and deceleration.
Receptors for equilibrium are hair cells in the utricle, saccule and semicircular canals and are collectively called vestibular apparatus.

70. Location and Structure of Receptors in the Maculae

71. Otolithic Organs: Saccule and Utricle
Macula- small thickened regions within the saccule and utricle.
Sensory structures for static equilibrium.
Also detect linear acceleration and deceleration.
Contain hair cells and supporting cells.
Stereocilia and kinocilium together called hair bundle.
Otolithic membrane rests on the hair cells and contain otoliths.

72. Static Labyrinth Utricle has macula oriented parallel to base of skull
Saccula has macula oriented perpendicular to base of skull
Macula: specialized epithelium of supporting columnar cells and hair cells with numerous stereocilia (microvilli) and one cilium (kinocilium) embedded in gelatinous mass weighted by otoliths
Gelatinous mass moves in response to gravity bending hair cells and initiating action potentials
Otoliths stimulate hair cells with varying frequencies
Patterns of stimulation translated by brain into specific information about head position or acceleration
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73. Physiology of Equilibrium continued
Tilting of the head forward→ sliding of the otolithic membrane bending the hair bundles→ receptor potential→ vestibular branch of the vestibulocochlear nerve.

74. Location and Structure of the Semicircular Ducts

75. Semicircular Ducts
Crista, a small elevation in the ampulla contain hair cells and supporting cells.
Cupula, a mass of gelatinous material covering the crista.
Head movement→ semicircular ducts and hair cells move with it→ hair bundles bend→ receptor potential→ nerve impulses→ vestibular branch of the vestibulocochlear nerve.

76. Cupula in Still Position versus Rotation

77. Kinetic Labyrinth
Three semicircular canals filled with endolymph: transverse plane, coronal plane, sagittal plane
Base of each expanded into ampulla with sensory epithelium (crista ampullaris)
Cupula suspended over crista hair cells. Acts as a float displaced by fluid movements within semicircular canals
Displacement of the cupula is most intense when the rate of head movement changes, thus this system detects changes in the rate of movement rather than movement alone.
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78. Equilibrium Pathway
Hair cells of utricle, saccule and semicircular ducts→
Vestibular branch of the vestibulocochlear nerve →brain stem → cerebellum and thalamus→ cerebral cortex.

79. End of lesson