1. Anatomy and Physiology, Sixth Edition
Rod R. Seeley Idaho State University
Trent D. Stephens Idaho State University
Philip Tate Phoenix College
Chapter 15
Lecture Outline*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Chapter 15
The Special Senses

3. Special Senses
Olfaction
Taste
Visual system
Hearing and balance

4. Olfaction Sense of smell Odors Olfactory neurons in this epithelium
Bipolar neurons
Olfactory hairs
Cilia which lies in mucous
Odors
Odorants bind to chemoreceptor molecules
Depolarize and initiate action potentials in neurons
Low threshold for odor detection

5. Neuronal Pathways of Olfaction

6. Taste Detected by taste buds Function Papillae Taste types Histology
Vallate
Fungiform
Foliate
Filiform
Histology
Support cells
Gustatory cells
Hairs
Function
Receptors on hairs detect dissolved substances
Taste types
Sour
Salty
Bitter
Sweet
Umami

7. Papillae and Taste Buds

8. Actions of Major Tastants

9. Neuronal Pathways for Taste

10. Visual System Eye Accessory structures Optic nerve (II)
Eyebrows, eyelids, eyelashes, tear glands
Protect eyes from sunlight and damaging particles
Optic nerve (II)
Tracts
Pathways
Eyes respond to light and initiate afferent action potentials

11. Accessory Structures of Eye
Eyebrows
Prevent running perspiration into eyes
Shade
Eyelids or palpebrae
Consist of 5 tissue layers
Protect and lubricate
Conjunctiva
Covers inner eyelid and anterior part of eye
Lacrimal apparatus
Extrinsic eye muscles

12. Lacrimal Apparatus Lacrimal apparatus Lacrimal Canaliculi Punctum
Lacrimal Gland: Produces tears to moisten, lubricate, wash
Lacrimal Canaliculi
Collects excess tears
Punctum
Lacrimal Sac
Nasolacrimal duct
Opens into nasal cavity

13. Extrinsic Eye Muscles

14. Anatomy of the Eye Three coats or tunics
Fibrous: Consists of sclera and cornea
Vascular: Consists of choroid, ciliary body, iris
Nervous: Consists of retina

15. Anatomy of the Eye Retina: Inner Fibrous tunic: Outer Compartments
Contains neurons sensitive to light
Macula lutea or fovea centralis: Area of greatest visual acuity
Optic disc: Blind spot
Compartments
Anterior: Aqueous humor
Posterior: Vitreous humor
Lens
Held by suspensory ligaments attached to ciliary muscles
Transparent, biconvex
Fibrous tunic: Outer
Sclera: White outer layer, maintains shape, protects internal structures, provides muscle attachment point, continuous with cornea
Cornea: Avascular, transparent, allows light to enter eye and bends and refracts light
Vascular tunic: Middle
Iris: Controls light entering pupil; smooth muscle
Ciliary muscles: Control lens shape; smooth muscle

16. Functions of the Complete Eye
Eye functions like a camera
Iris allows light into eye
Lens, cornea, humors focus light onto retina
Light striking retina is converted into action potentials relayed to brain

17. Light
Visible light: Portion of electromagnetic spectrum detected by human eye
Refraction: Bending of light
Divergence: Light striking a concave surface
Convergence: Light striking a convex surface
Focal point: Point where light rays converge and cross

18. Focus and Accommodation
Emmetropia: Normal resting condition of lens
Far vision: 20 feet or more from eye
Near vision: Closer than 20 feet
Accommodation
Pupil constriction
Convergence

19. The Retina Provides black backdrop for increasing visual acuity
Sensory retina and pigmented retina
Photoreceptors
Rods: Noncolor vision
Rhodopsin reduction: Light adaptation
Rhodopsin production: Dark adaptation
Cones: Color vision

20. Sensory Receptor Cells

21. Rhodopsin Cycle

22. Rod Cell Hyperpolarization

23. Visual Pathways

24. Eye Disorders Myopia: Nearsightedness Retinal detachment Glaucoma
Focal point too near lens, image focused in front of retina
Hyperopia: Farsightedness
Image focused behind retina
Presbyopia
Degeneration of accommodation, corrected by reading glasses
Astigmatism: Cornea or lens not uniformly curved
Strabismus: Lack of parallelism of light paths through eyes
Retinal detachment
Can result in complete blindness
Glaucoma
Increased intraocular pressure by aqueous humor buildup
Cataract
Clouding of lens
Macular degeneration
Common in older people, loss in acute vision
Diabetes
Dysfunction of peripheral circulation

25. The Ear External ear: Hearing; terminates at eardrum
Middle ear: Hearing; contains auditory ossicles
Inner ear: Hearing and balance; interconnecting fluid-filled tunnels and chambers

26. The Ear External ear Middle ear Oval window
Auricle or pinna: elastic cartilage
External auditory meatus
Lined with hairs and ceruminous glands
Tympanic membrane
Vibrated by sound waves
Middle ear
Auditory or eustachian tube
Opens into pharynx, equalizes pressure
Ossicles: malleus, incus, stapes: transmit vibrations
Oval window

27. Inner Ear Labyrinth -Lymphs Bony Membranous Endolymph Perilymph
Cochlea: Hearing
Vestibule: Balance
Semicircular canals: Balance
Membranous
-Lymphs
Endolymph
In membranous labyrinth
Perilymph
Space between membranous and bony labyrinth

28. Structure of Cochlea

29. Auditory Function Vibrations produce sound waves
Volume or loudness : Function of wave amplitude
Pitch: Function of wave frequency
Timbre: Resonance quality or overtones of sound

30. Effect of Sound Waves on Cochlear Structures

31. CNS Pathways for Hearing

32. Balance Static Kinetic Evaluates position of head relative to gravity
Detects linear acceleration and deceleration
Utricle and saccule
Maculae: Consist of hairs embedded in gelatinous mass containing otoliths
Kinetic
Evaluates movements of head
3 semicircular canals
Ampulla
Crista ampullaris
Cupula: endolymph moves when head moves

33. Structure of the Macula

34. Vestibule in Maintaining Balance

35. Semicircular Canals

36. CNS Pathways for Balance

37. Ear Disorders Tinnitus Motion sickness Otitis Media Earache
Ringing, clicking, whistling in ear due to disorders in middle or inner ear
Motion sickness
Dysfunctions caused by stimulation of semicircular canals during motion
Otitis Media
Infections in the middle ear
Earache
Results from otitis media, dental abscesses, TMJ pain

38. Effects of Aging on the Special Senses
Slight loss in ability to detect odors
Decreased sense of taste
Lenses of eyes lose flexibility
Development of cataracts, macular degeneration, glaucoma, diabetic retinopathy
Decline in visual acuity and color perception