1. Chapter 11
The Senses

2. Sense Organs, and the Eye
Lesson 11.1
Sense Organs, and the Eye
Classify sense organs as special or general and explain the basic differences between the two groups.
Discuss how a stimulus is converted into a sensation.
Discuss the general sense organs and their functions.
Describe the structure of the eye and the functions of its components.
Name and describe the major visual disorders.

3. General Sense Organs Often exist as individual cells or receptor units
Widely distributed throughout the body
Different from special sense organs—groupings of receptors within highly complex organs

4. Special Sense Organs Large and complex organs
Localized grouping of specialized receptors

5. Classification of Sense Organs
Classification by presence or absence of covering capsule
Encapsulated
Unencapsulated (“free” or “naked”)

6. Classification of Sense Organs
Classification by type of stimuli required to activate receptors
Photoreceptors (light)
Chemoreceptors (chemicals)
Pain receptors (injury)
Thermoreceptors (temperature change)
Mechanoreceptors (movement or deforming of capsule)
Proprioceptors (position of body parts or changes in muscle length or tension)

7. Converting a Stimulus into a Sensation
All sense organs have common functional characteristics
All are able to detect a particular stimulus
A stimulus is converted into a nerve impulse
A nerve impulse is perceived as a sensation in the CNS

8. General Sense Organs
Distribution is widespread; single-cell receptors are common
Skin receptors
Free nerve endings (several types)—pain, discriminative touch, tickle, and temperature
Tactile (Meissner) corpuscle—fine touch and vibration
Bulbous (Ruffini) corpuscle—touch and pressure
Lamellar (Pacini) corpuscle—pressure and vibration
Bulboid (Krause) corpuscle—touch

9. General Sense Receptors

10. General Sense Organs Muscle receptors Deep receptors
Golgi tendon receptor—proprioception
Muscle spindle—proprioception
Deep receptors
Stretch (pressure) receptors in hollow organs
Chemical receptors—detect pH, carbon dioxide, other chemicals
Third-degree burns can completely destroy general sense receptors throughout affected area
Temporary impairment of general sense receptors occurs when blood flow to them is slowed

11. External Eye Structures

12. The Eye Layers of eyeball
Sclera—tough outer coat; “white” of eye; cornea is transparent part of sclera over iris
Choroid—pigmented vascular layer prevents scattering of light
Front part of this layer made of ciliary muscle and iris, the colored part of the eye
The pupil is the hole in the center of the iris
Retina—innermost layer of the eye; contains rods (monochrome receptors for night vision) and cones (color receptors for day vision)

13. Components of the Eye

14. The Eye and Vision
Function of the iris. Contraction of iris muscle dilates or constricts pupil 14

15. The Eye & Eye Fluids
Conjunctiva—mucous membrane covering the front surface of the sclera and lining the eyelid
Lens—transparent body behind the pupil; focuses light rays on the retina
Aqueous humor—in the anterior cavity in front of the lens
Vitreous humor—in the posterior cavity behind the lens

16. Cells of the Retina

17. The Eye and Vision structures
Fovea- a small depression in the macula near the center of the retina
The site of acute image formation and color vision
Optic disc- where the optic nerve muscles exit the eye 17

18. Retinal (Fundus) of the Left Eye

19. Shaken Baby Syndrome
Courtesy Stephen Ludwig, MD. Children’s Hospital of Philadelphia. In Zitelli, Davis: Atlas of pediatric physical diagnosis, ed 6, Mosby, 2012, St Louis.

20. The Eye and Vision (cont.)
Pathway of Light Rays and Refraction
Transparent parts of the eye that refract light
Cornea
Aqueous humor
Crystalline lens
Vitreous body

21. Visual Pathway Innermost layer of retina contains rods and cones
Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina

22. Visual Pathway
Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a blind spot
Visual interpretation occurs in the visual cortex of the cerebrum

23. Visual Pathway

24. Visual Disorders Refraction disorders
Myopia (nearsightedness) is often caused by elongation of the eyeball
Hyperopia (farsightedness) is often caused by a shortened eyeball
Astigmatism is distortion caused by an irregularity of the cornea or lens
Cataracts are cloudy spots in the eye's lens

25. Refraction

26. Refraction Disorders
Conjunctivitis (inflammation of the conjunctiva) can interfere with refraction
Trachoma—chronic chlamydial infection
Acute bacterial conjunctivitis—highly contagious infection that produces a discharge of mucous pus
Conjunctivitis can be caused by allergies
Strabismus—improper alignment of eyes
Eyes can converge (cross) or diverge
If not corrected, can cause blindness

27. Visual Disorders Sty Cataract
From Swartz MH: Textbook of physical diagnosis, ed 6, Philadelphia, 2010, Saunders.
From Palay DA, Krachmer JH: Ophthalmology for the primary care physician, St Louis, 1997, Mosby.

28. Acute Bacterial Conjunctivitis
From Newell FW: Ophthalmology: principles and concepts, ed 8, St Louis, 1996, Mosby.

29. Muscles of the Eye Adjust eye so the retina receives clear image
Extrinsic muscles
Outer surface of eyeball
Voluntary
Control convergence for three-dimensional vision

30. Extrinsic muscles of the eye30

31. Strabismus
Seidel H et al: Mosby’s guide to physical examination, ed 3, St Louis, 2002, Mosby.

32. The Eye and Vision (cont.)
Nerve Supply to the Eye
Sensory
Optic nerve (CN II)
Ophthalmic branch of trigeminal nerve (CN V)
Motor
Oculomotor nerve (CN III)
Trochlear (CN IV)
Abducens (CN VI)

33. Disorders of the Retina
Retinal detachment can be a complication of aging, eye tumors, or head trauma
Diabetic retinopathy—damage to retina from hemorrhages and growth of abnormal vessels associated with diabetes mellitus
Glaucoma—increased intraocular pressure decreases blood flow in retina and thus causes retinal degeneration
Age-related macular degeneration (AMD) —progressive degeneration of the central part of the retina

34. Retinal detachment 34

35. Retinal disorders. 35

36. Disorders of the Retina
Nyctalopia (night blindness) or the inability to see in dim light is caused by retinal degeneration or lack of vitamin A
Color blindness—most forms inherited
Red-green color blindness is an X-linked genetic condition involving the inability to perceive certain colors
It is caused by an abnormality in the cones’ photopigments

37. Color Vision Screening Figures
From Ishihara’s tests for colour deficiency, Tokyo, Japan, 1973, Kanehara Trading Co, Copyright Isshinkai Foundation.

38. Disorders of the Visual Pathway
Scotoma is the loss of only the central visual field when only certain nerve pathways are damaged
Cerebrovascular accidents (CVAs) can damage visual processing centers; example is acquired cortical color blindness

39. The Ear, and Taste and Smell Receptors
Lesson 11.2
The Ear, and Taste and Smell Receptors
Discuss the anatomy of the ear and its sensory function in hearing and equilibrium.
Name and describe the major forms of hearing impairment.
Discuss the chemical receptors and their functions.

40. The Ear Sense organ of hearing and also of equilibrium and balance
Divisions of the ear:
External ear
Middle ear
Inner (internal) ear

41. External Ear Auricle (pinna)—appendage on side of head
External acoustic canal
Curving tube 2.5 cm (1 inch) in length
Contains ceruminous glands
Ends at the tympanic membrane

42. Examining the Ear

43. Middle Ear
Epithelium-lined cavity that houses the ear ossicles—malleus, incus, and stapes
Ends in the oval window
The auditory (eustachian) tube connects the middle ear to the throat
Inflammation called otitis media

44. Acute Otitis Media

45. The Ear

46. Inner Ear Bony labyrinth filled with perilymph
Subdivided into the vestibule, semicircular canals, and cochlea
Membranous labyrinth filled with endolymph
The receptors for balance in the semicircular canals are called cristae ampullaris
Sensory hair cells on the organ of Corti (spiral organ) respond when bent by the movement of surrounding endolymph set in motion by sound waves

47. The Inner Ear

48. Effect of Sound Waves on Cochlear Structures

49. Effect of Sound Waves on Cochlear Structures49

50. Equilibrium
Ciliated equilibrium sensory receptors (mechanoreceptors) are located in vestibule and semicircular canals.
Types of receptors
Maculae
Cristae
Nerve supply via vestibular nerve

51. The Ear Action of the vestibular equilibrium receptors (maculae).51

52. The Ear Action of the equilibrium receptors (cristae) in the semicircular canals.52

53. Hearing Disorders Conduction impairments
Can be caused by blockage of the external or middle ear (for example, by cerumen and tumors)
Otosclerosis—inherited bone disorder involving irregularity of the stapes; it first appears as tinnitus (ringing) then progresses to hearing loss
Otitis—ear inflammation caused by infection; can produce swelling and fluids that block sound conduction

54. Nerve Impairment Equilibrium Disorders
Presbycusis—progressive nerve deafness associated with aging
Progressive nerve deafness can also result from chronic exposure to loud noise
Equilibrium Disorders
Often characterized by vertigo, disorientation, falling, dizziness, or lightheadedness
Some are caused by infection or inflammation of inner ear
Ménière disease—chronic inner ear disorder characterized by tinnitus, nerve deafness, and vertigo

55. The Taste Receptors Receptors are chemoreceptors called taste buds
Cranial nerves VII and IX carry gustatory impulses
Only four kinds of taste sensations
Sweet
Sour
Bitter
Salty
Gustatory and olfactory senses work together

56. The Tongue

57. The Smell Receptors
Receptors for fibers of olfactory (cranial nerve I) lie in olfactory mucosa of nasal cavity
Olfactory receptors are extremely sensitive but easily fatigued
Odor-causing chemicals initiate a nervous signal that is interpreted as a specific odor by the brain

58. Olfactory Structures

59. Integration of Senses Senses are all perceived by the brain
All incoming signals are integrated with other sensory signals and even memories to produce our perceptions
Severe nasal congestion can interfere with stimulation of olfactory receptors, preventing foods from having full flavor
Advancing age often brings a structural degeneration that results in reduced function