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Chapter 17
THE SPECIAL SENSES
Chapter Synopsis
Included among the special senses are smell, taste, sight, hearing, and equilibrium. .In
contrast to the general senses, the special senses have highly complex receptor
organs. The detailed anatomy and physiology of the special senses are discussed.
The development of the eyes and ears are also discussed. Disorders include
cataracts, glaucoma, macular degeneration, deafness, Menier’s disease, and otitis
media. Clinical applications include hyposmia, taste aversions, age related macular
damage, LASIK, detached retina, presbyopia, and otosclerosis.
Chapter Outline and Objectives
INTRODUCTION
1. Briefly describe the receptors for the special senses.
OLFACTION: SENSE OF SMELL
2. Discuss the interconnection of the senses of smell and taste.
Anatomy of Olfactory Receptors
3. Discuss the anatomic relation of cells in the olfactory mucosa and describe
the cellular parts with respect to function.
Physiology of Olfaction
4. Describe the sequence of events in which a molecule that comes in contact
with mucus of the epithelium initiates an action potential.
Odor Thresholds and Adaptation
5. Explain the result of olfactory nerve adaptation on sensory nerve output and
how it is useful in discriminative sensory sensitivity.
Olfactory Pathway
6. Describe the neural links from the bipolar olfactory receptor to their
destinations in specific functional areas of the brain.
7. Define hyposmia and state its causes.
GUSTATION: SENSE OF TASTE
8. Discuss the general similarities and differences in operation of the gustatory
and olfactory systems, then relate how they work together.
Anatomy of Taste buds and Papillae
9. Describe the organization and functional parts of the cells within the various
taste buds, indicating the differing cellular duties and etiological
transformations.
Physiology of Gustation
10. Describe the means by which the binding of a dissolved molecule in saliva
generates a postsynaptic potential in the primary sensory neuron.
11. Describe how the gustatory system discriminates among hundreds of different
tastes with only four types of taste receptors.
Taste Thresholds and Adaptation
12. Discuss how the taste threshold changes with adaptation.
Gustatory Pathway
13. Indicate which cranial nerves conduct taste impulses from separate regions of
the tongue to specific areas of the brain.
14. Describe tase aversion and correlate this phenomenon to survival.
VISION
Accessory Structures of the Eye
Eyelids
15. Describe the structures of the eyelids and their functions.
Eyelashes and Eyebrows
16. Describe the eyelashes and eyebrows and their functions.
Lacrimal Apparatus
17. Describe the structures of the lacrimal apparatus and their functions.
Extrinsic Eye Muscles
18. Identify the extrinsic eye muscles and their functions.
Anatomy of the Eyeball
Fibrous Tunic
19. Describe the tissue configurations and related jobs of the components of the
fibrous tunic.
20. Discuss the procedure of and implications for LASIK.
Vascular Tunic
21. Describe the structural constituents of the three regions of the vascular tunic,
while emphasizing how these allow performance of their distinct duties.
Retina
22. Describe the major features and layers of the nervous tunic.
23. Discuss the positions of extensions and soma of two types of photo-receptor
cells and three varieties of retinal neurons that compose the numerous layers
within the retina.
24. Discuss the general purpose of the different retinal cells.
Lens
25. Describe the structure and function of the lens.
Interior of the Eyeball
26. Describe the materials that occupy the cavities and chambers of the inner
eye, and state how the materials support the operation of the eye.
27. Discuss age related macular disease and examine its effects on vision.
Image Formation
28. Discuss how components of the eyeball mimic the parts of a camera to
perform the three basic processes in properly focusing light on the retina.
Refraction of Light Rays
29. Discuss how the bending of light as it passes through the differing densities of
transparent materials of the eye is used to direct the rays from objects of
varying distance to focus on the retina.
Accommodation and the Near Point of Vision
30. Demonstrate how the iris, lens, and extrinsic eye muscles operate in order to
converge the light from a near object onto the retina.
31. Examine the effect on image formation when there are abnormal changes in
the structure of the cornea and lens.
32. Discuss age related changes in elasticity and their effects on accomodation
as seen in presbyopia.
Refraction Abnormalities
33. List and discuss the refraction abnormalities.
Constriction of the Pupil
34. Outline the components of the iris control mechanism, and their operation and
purpose in altering the diameter of the pupil.
Convergence
35. Illustrate how and why the relative forward angle of the eyes varies as an
object of interest changes distance.
Physiology of Vision
Photoreceptors and Photopigments
36. Describe the definitive structures and operations of rod and cone
photoreceptors as well as the location and differences between
photopigments.
37. List the steps of the configuration changes that occur to the photopigments
upon absorption of a photon.
Light and Dark Adaptation
38. Indicate how the timing of photopigment regeneration leads to different
capacities in rods and cones to adapt to changes in light intensity.
Release of Neurotransmitters by Photoreceptors
39. Discuss the sequence of interactions between photopigments, enzymes,
sodium channels, photoreceptor membrane potential, glutamate release, and
changes in the membrane potential of connected bipolar cells.
Visual Pathway
40. Mention that the signal produced by the photoreceptors is progressively
integrated as it moves through the circuits leading to the brain.
Processing of Visual Input in the Retina
41. Discuss how the type of circuit connections of rods and cones to other retinal
neurons dictates differences in light sensitivity and clarity of the image
invoked by the two types of photoreceptors.
Brain Pathway and Visual Fields
42. Diagram the relationship that results in stereoscopic vision from light
originating from specific visual fields with the area of the retina that receives it
and the alternate pathways of the associated neurons.
HEARING AND EQUILIBRIUM
Anatomy of the Ear
External (Outer) Ear
43. Describe the tissue structures and functions of the auricle and auditory canal.
Middle Ear
44. Discuss the anatomy, operations, and functions of middle ear structures from
the tempanic membrane to the oval window.
45. Explain why the ossicles amplify the force of vibrations by a factor of thirty
from the eardrum to the stapes.
46. State some functional responsibilities of internal auditory tube.
Internal (Inner) Ear
47. Illustrate how the bony and membranous labyrinths fit together to form the
modules of the semicircular canals, vestibule, and cochlear apparatus.
48. Examine the specialized structures of the sensory mechanisms of the
semicircular canals, vestibule, and cochlear apparatus.
Nature of Sound Waves
49. Establish the physical relations of sound wave length to frequency and pitch,
and amplitude to loudness measured in decibels.
50. Describe how loud sounds damage hair cells.
Physiology of Hearing
51. Discuss the principal structures and events that transform differing sound
vibration frequencies into impulses traveling along separate cochlear
neurons, which are involved with the physiology of hearing.
Auditory Pathway
52. Describe the components of the auditory pathway.
53. Discuss how cochlear implants can be used for people with deafness due to
injury to hair cells.
Physiology of Equilibrium
54. Distinguish between the two kinds of equilibrium.
Otolithic Organs: Saccule and Utricle
55. Describe the cellular and extracellular constituents of the maculae, and the
relative spacial position of these otoliths organs with the saccule and utricle.
56. Discuss how the otoliths work with the cilia of the macular hair cells to
indicate relative orientation to gravity and direction of acceleration.
Semicircular Ducts
57. Describe how the fluid of the semicircular canals temporarily moves against
the cupula of the ampula to incite impulses that indicate three dimensions of
rotational movement.
Equilibrium Pathways
58. Define the distribution of the cochlear and vestibular components of cranial
nerve VI to the nuclei for vision and head orientation, and to the cerebellum
for integration with information on movement control.
DEVELOPMENT OF THE EYES AND EARS
Eyes
59. Describe the embryological development of the eyes.
Ears
60. Describe the embryological development of the ears.
AGING AND THE SPECIAL SENSES
61. Discuss the effects of aging on the senses of smell, taste, hearing, and vision.
DISORDERS: HOMEOSTATIC IMBALANCES
62. Describe the causes and symptoms of cataracts, glaucoma, deafness,
Menier’s disease, and otitis media.
MEDICAL TERMINOLOGY
63. Define medical terminology associated with sense organs.