Chapter 16: Chapter 16: The Special The Special Senses Senses 1. 1. Describe the Describe the structures of the structures of the Special Senses Special Senses 2. 2. Explain the pathways Explain the pathways of sound in the ear of sound in the ear and light in the eye and light in the eye 3. 3. Identify, describe, Identify, describe, and discuss the and discuss the receptors and neural receptors and neural pathways involved in pathways involved in each of the five each of the five special senses special senses Chapter objectives: Chapter objectives: 1. 1. Taste Taste 2. 2. Smell Smell 3. 3. Sight Sight 4. 4. Hearing Hearing 5. 5. Touch (Chapt Touch (Chapt 14) 14) Chemical Chemical Senses Senses
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Chapter 16: Chapter 16:
The Special SensesThe Special Senses
1.1. Describe the structures of Describe the structures of the Special Sensesthe Special Senses
2.2. Explain the pathways of Explain the pathways of sound in the ear and light in sound in the ear and light in the eye the eye
3.3. Identify, describe, and Identify, describe, and discuss the receptors and discuss the receptors and neural pathways involved in neural pathways involved in each of the five special each of the five special senses senses
Chemoreceptors in Chemoreceptors in Taste BudsTaste Buds– Mostly in papillae on the tongueMostly in papillae on the tongue
Circumvallate, fungiformCircumvallate, fungiform Each has groups of Each has groups of gustatory gustatory
cellscells Sweet, Sour, Salt, Bitter, UmamiSweet, Sour, Salt, Bitter, Umami CN VII and IX to medulla oblongataCN VII and IX to medulla oblongata
The Chemical Senses: The Chemical Senses: 1. Taste1. Taste
The Chemical Senses: The Chemical Senses: 1. Taste1. Taste
The Chemical Senses: The Chemical Senses: 2. Smell2. Smell
Olfactory EpitheliumOlfactory Epithelium– Receptors in pseudostratified Receptors in pseudostratified
epithelium in nasal conchae epithelium in nasal conchae and septumand septum
Filaments from OE protrude Filaments from OE protrude through the Cribriform Platethrough the Cribriform Plate– CN I runs to the Olfactory CN I runs to the Olfactory
Bulb, and to the olfactory Bulb, and to the olfactory cortex of the cerebrumcortex of the cerebrum
Factoids:Factoids:Most dominant senseMost dominant sense
70% of the body’s receptors 70% of the body’s receptors are in the eyesare in the eyes40% of cortex dedicated to 40% of cortex dedicated to visual processingvisual processingMost metabolically active Most metabolically active tissuetissue
Only site where CNS can be Only site where CNS can be seenseenMedical careers:Medical careers:
Vision (Eye and Accessories)Vision (Eye and Accessories)
Dissected ViewDissected View
Continuation of skinContinuation of skin
EyelashesEyelashes
Tarsal Plate of Hyaline C.Tarsal Plate of Hyaline C.
Tarsal (Meibomian) glands Tarsal (Meibomian) glands on on inner margin of lidinner margin of lid– The oily portion of the tear filmThe oily portion of the tear film– Swollen gland = chalazionSwollen gland = chalazion
Conjunctiva Conjunctiva (= mucous membrane)(= mucous membrane)– Palpebral or BulbarPalpebral or Bulbar– Over cornea very thin (5-7 cells Over cornea very thin (5-7 cells
Lacrimal puncta Lacrimal puncta (superior and (superior and inferior) - holes next to the medial inferior) - holes next to the medial canthus to drain tearscanthus to drain tears
Nasolacrimal duct - empties to nasal Nasolacrimal duct - empties to nasal cavitycavity
•ConesCones•Concentrated in maculaConcentrated in macula•Color vision –red, green Color vision –red, green blueblue
Fig 16.10
Chambers of the EyeChambers of the Eye
Posterior SegmentPosterior Segment
– Vitreous HumorVitreous Humor
Anterior Segment—filled with Anterior Segment—filled with aqueous humoraqueous humor
– Anterior chamber = between Anterior chamber = between iris and corneairis and cornea
– Posterior Chamber = Posterior Chamber = between lens and irisbetween lens and iris
Posterior cavity with Posterior cavity with vitreous humorvitreous humor
Vision Terminology Vision Terminology p 494p 494
Emmetropia = Normal visionEmmetropia = Normal vision Hyperopia = FarsightednessHyperopia = Farsightedness Myopia = NearsightednessMyopia = Nearsightedness Presbyopia = Poor close-up vision with Presbyopia = Poor close-up vision with
agingaging Astigmatism = Abnormal shape of the Astigmatism = Abnormal shape of the
surface of the lens and/or corneasurface of the lens and/or cornea Cataract = abnormal crystallization of the Cataract = abnormal crystallization of the
lens, common in diabetes, injury, hereditylens, common in diabetes, injury, heredity Amblyopia = Poor vision in a normal eye Amblyopia = Poor vision in a normal eye
(CNS defect)(CNS defect)
Visual PathwayOptic chiasma - optic nerves partially Optic chiasma - optic nerves partially cross (right side of the field of each eye cross (right side of the field of each eye combining and going to the lateral combining and going to the lateral geniculate on the right, those from the geniculate on the right, those from the left to the left) left to the left)
To superior colliculus and thalamus To superior colliculus and thalamus and visual cortex in occipital lobeand visual cortex in occipital lobe
The EarThe Ear
HearingHearingBalance (equilibrium)Balance (equilibrium)CN VIIICN VIII
•Three Three semicircular canals semicircular canals with ampullae (mutually with ampullae (mutually perpendicular)perpendicular)
•Linear accelerationLinear acceleration
Each has a Each has a macula with macula with receptorsreceptors
Two Receptor Organs of vestibuleTwo Receptor Organs of vestibule
•Two Maculae Two Maculae •or: macula of saccule or: macula of saccule plus macula of utricleplus macula of utricle•Vertical and horizontal Vertical and horizontal orientationorientation•Contain otoliths that Contain otoliths that move according to gravitymove according to gravity•Hair cells conduct Hair cells conduct impulse to CN VIIIimpulse to CN VIII