1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 12 Lecture PowerPoint

2. 2 Type Course Number Here: Type Course Name Here Chapter 12 Type Professor Name Here Type Academic Rank Here Type Department Name Here Type Institution Name Here

3. 3 Hole’s Human Anatomy and Physiology Twelfth Edition Shier  Butler  Lewis Chapter 12 Nervous System III: Senses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4. 4 12.1: Introduction General senses Receptors that are widely distributed throughout the body Skin, various organs and joints Special senses Specialized receptors confined to structures in the head Eyes, ears, nose and mouth

5. 5 12.2: Receptors, Sensation, and Perception Sensory receptors Specialized cells or multicellular structures that collect information from the environment Stimulate neurons to send impulses along sensory (afferent) fibers to the brain Sensation A feeling that occurs when brain becomes aware of sensory impulse Perception A person’s view of the stimulus; the way the brain interprets the information

6. 6 Pathways From Sensation to Perception (Example of an Apple)

7. 7 Receptor Types Chemoreceptors Respond to changes in chemical concentrations Pain receptors (nociceptors) Respond to chemicals released during tissue damage Thermoreceptors Respond to changes in temperature Mechanoreceptors Respond to mechanical forces (touch, stretch, pressure) Photoreceptors Respond to light

8. 8 Sensory Impulses Stimulation of receptor causes local change in its receptor potential A graded electrical current is generated that reflects intensity of stimulation If receptor is part of a neuron, the membrane potential may generate an action potential If receptor is not part of a neuron, the receptor potential must be transferred to a neuron to trigger an action potential Peripheral nerves transmit impulses to CNS where they are analyzed and interpreted in the brain

9. 9 Sensations and Perception Projection Process in which the brain projects the sensation back to the apparent source It allows a person to pinpoint the region of stimulation

10. 10 Sensory Adaptation Ability to ignore unimportant stimuli Involves a decreased response to a particular stimulus from the receptors (peripheral adaptation) or along the CNS pathways leading to the cerebral cortex (central adaptation) Sensory impulses become less frequent and may cease Stronger stimulus is required to trigger impulses

11. 11 12.3: General Senses Senses associated with skin, muscles, joints and viscera Three (3) groups: Exteroceptive senses (exteroceptors) Senses associated with body surface such as touch, pressure, temperature, and pain Visceroceptive senses (interoceptors) Senses associated with changes in the viscera such as blood pressure stretching blood vessels and ingestion of a meal Proprioceptive senses Senses associated with changes in muscles and tendons such as at joints

12. 12 Touch and Pressure Senses Free nerve endings Common in epithelial tissues Simplest receptors Sense itching Tactile (Meissners) corpuscles Abundant in hairless portions of skin and lips Detect fine touch; distinguish between two points on the skin Lamellated (Pacinian) corpuscles Common in deeper subcutaneous tissues, tendons and ligaments Detect heavy pressure and vibrations

13. 13 Touch and Pressure Receptors Epidermis Dermis (a) (b) (c) Section of skin Free nerve endings Epithelial cells Sensory (afferent) nerve fiber Epithelial cells Tactile (Meissners) corpuscle (touch receptor) Sensory (afferent) nerve fiber Lamellated (Pacinian) corpuscle (pressure receptor) Connective tissue cells Sensory (afferent) nerve fiber Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Ed Reschke

14. 14 Temperature Senses Warm receptors Sensitive to temperatures above 25 o C (77 o F) Unresponsive to temperature above 45 o C (113 o F) Cold receptors Sensitive to temperatures between 10 o C (50 o F) and 20 o C (68 o F) Pain receptors Respond to temperatures below 10 o C Respond to temperatures above 45 o C

15. 15 Sense of Pain Free nerve endings Widely distributed Nervous tissue of brain lacks pain receptors Stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature Adapt very little, if at all

16. 16 Visceral Pain Pain receptors are the only receptors in viscera whose stimulation produces sensations Pain receptors respond differently to stimulation Pain receptors are not well localized Pain receptors may feel as if coming from some other part of the body Known as referred pain…

17. 17 Referred Pain May occur due to sensory impulses from two regions following a common nerve pathway to brain Appendix Ureter Lung and diaphragm Heart Stomach Pancreas Colon Kidney Urinary bladder Liver and gallbladder Small intestine Ovary (female) Liver and gallbladder Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18. 18 Pain Nerve Pathways Acute pain fibers A-delta fibers Thin, myelinated Conduct impulses rapidly Associated with sharp pain Well localized Chronic pain fibers C fibers Thin, unmyelinated Conduct impulses more slowly Associated with dull, aching pain Difficult to pinpoint Blocked by narcotics (controlled substances) CCC (Chronic, C fibers, Controlled substances)

19. 19 Regulation of Pain Impulses Thalamus Allows person to be aware of pain Cerebral cortex Judges intensity of pain Locates source of pain Produces emotional and motor responses to pain Pain inhibiting substances: Enkephalins Serotonin Endorphins

20. 20 12.1 Clinical Application Treating Pain

21. 21 Proprioception Mechanoreceptors Send information to spinal cord and CNS about body position and length, and tension of muscles Main kinds of proprioceptors: Pacinian corpuscles – in joints Muscle spindles – in skeletal muscles* Golgi tendon organs – in tendons* *considered to be stretch receptors

22. 22 Stretch Receptors (a) Muscle spindle Skeletal muscle fiber Golgi tendon organ Tendon (b) Sensory (afferent) nerve fiber Sensory nerve endings Sensory (afferent) nerve fiber Connective tissue sheath Intrafusal fiber Skeletal muscle fiber Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23. 23 Visceral Senses Receptors in internal organs Convey information that includes the sense of fullness after eating a meal as well as the discomfort of intestinal gas and the pain that signals a heart attack

24. 24 Summary of Receptors of the General Senses

25. 25 12.4: Special Senses Sensory receptors are within large, complex sensory organs in the head Smell in olfactory organs Taste in taste buds Hearing and equilibrium in ears Sight in eyes

26. 26 Sense of Smell Olfactory receptors Chemoreceptors Respond to chemicals dissolved in liquids Olfactory organs Contain olfactory receptors and supporting epithelial cells Cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

27. 27 Olfactory Receptors Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nasal cavity Cilia (b) (a) Cribriform plate Olfactory area of nasal cavity Superior nasal concha Olfactory bulb Olfactory tract Nerve fibers within the olfactory bulb Olfactory receptor cells Columnar epithelial cells Cribriform plate

28. 28 Olfactory Nerve Pathways Once olfactory receptors are stimulated, nerve impulses travel through Olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

29. 29 Olfactory Stimulation Olfactory code Hypothesis Odor that is stimulated by a distinct set of receptor cells and its associated receptor proteins Olfactory organs located high in the nasal cavity above the usual pathway of inhaled air Olfactory receptors undergo sensory adaptation rapidly Sense of smell drops by 50% within a second after stimulation

30. 30 12.2 Clinical Application Mixed-Up Senses: Synesthesia

31. 31 Sense of Taste Taste buds Organs of taste Located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx Taste receptors Chemoreceptors Taste cells – modified epithelial cells that function as receptors Taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

32. 32 Taste Receptors Papillae (a) (b) Connective tissue Sensory (afferent) nerve fibers Epithelium of tongue Supporting cell Taste pore Taste hair Taste cell Taste buds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

33. 33 Taste Sensations Four primary taste sensations Sweet – stimulated by carbohydrates Sour – stimulated by acids Salty – stimulated by salts Bitter – stimulated by many organic compounds Spicy foods activate pain receptors

34. 34 Taste Nerve Pathways Sensory impulses from taste receptors travel along: Cranial nerves VII, IX, and X to… Medulla oblongata to… Thalamus to… Gustatory cortex (for interpretation)

35. 35 12.3 Clinical Application Smell and Taste Disorders

36. 36 Sense of Hearing Ear Organ of hearing Three (3) sections: External ear Middle ear Inner ear

37. 37 External Ear Auricle Collects sounds waves External auditory meatus Lined with ceruminous glands Carries sound to tympanic membrane Terminates with tympanic membrane Tympanic membrane Vibrates in response to sound waves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Round window Pharynx Auditory tube Auricle Oval window (under stapes) Cochlea Malleus Incus Stapes External acoustic meatus Semicircular canals Vestibulocochlear nerve Tympanic cavity Tympanic membrane

38. 38 Middle Ear Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Round window Pharynx Auditory tube Auricle Oval window (under stapes) Cochlea Malleus Incus Stapes External acoustic meatus Semicircular canals Vestibulocochlear nerve Tympanic cavity Tympanic membrane Tympanic cavity Air-filled space in temporal bone Auditory ossicles Vibrate in response to tympanic membrane Malleus, incus and stapes Hammer, anvil and stirrup Oval window Opening in wall of tympanic cavity Stapes vibrates against it to move fluids in inner ear

39. 39 Auditory Tube Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Round window Pharynx Auditory tube Auricle Oval window (under stapes) Cochlea Malleus Incus Stapes External acoustic meatus Semicircular canals Vestibulocochlear nerve Tympanic cavity Tympanic membrane Also known as the Eustachian tube Connects middle ear to throat Helps maintain equal pressure on both sides of tympanic membrane Usually closed by valve- like flaps in throat

40. Inner Ear Complex system of labyrinths Osseous labyrinth Bony canal in temporal bone Filled with perilymph Membranous labyrinth Tube within osseous labyrinth Filled with endolymph Cochlear nerve Maculae Utricle (a) Cochlea Saccule Ampullae Endolymph Perilymph Membranous labyrinth Bony labyrinth Vestibular nerve Scala vestibuli (cut) Scala tympani (cut) Cochlear duct (cut) containing endolymph VestibuleOval window Round window Semicircular canals Bony labyrinth (contains perilymph) Membranous labyrinth (contains endolymph) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 40

41. Inner Ear Cochlear nerve Maculae Utricle (a) Cochlea Saccule Ampullae Endolymph Perilymph Membranous labyrinth Bony labyrinth Vestibular nerve Scala vestibuli (cut) Scala tympani (cut) Cochlear duct (cut) containing endolymph VestibuleOval window Round window Semicircular canals Bony labyrinth (contains perilymph) Membranous labyrinth (contains endolymph) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 41 Three (3) parts of labyrinths: Cochlea Functions in hearing Semicircular canals Functions in equilibrium Vestibule Functions in equilibrium

42. 42 Cochlea Scala vestibuli Upper compartment Leads from oval window to apex of spiral Part of bony labyrinth Scala tympani Lower compartment Extends from apex of the cochlea to round window Part of bony labyrinth Stapes vibrating in oval window Scala vestibuli filled with perilymph Vestibular membrane Basilar membrane Scala tympani filled with perilymph Round window Helicotrema Membranous labyrinth Cochlear duct filled with endolymph Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43. 43 Cochlea Cochlear duct Portion of membranous labyrinth in cochlea Vestibular membrane Separates cochlear duct from scala vestibuli Basilar membrane Separates cochlear duct from scala tympani Spiral organ (organ of Corti) Basilar membrane (a) Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Scala tympani (contains perilymph) Branch of cochlear nerve Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

44. 44 12.4 Clinical Application Getting a Cochlear Implant

45. 45 Organ of Corti Group of hearing receptor cells (hair cells) On upper surface of basilar membrane Different frequencies of vibration move different parts of basilar membrane Particular sound frequencies cause hairs of receptor cells to bend Nerve impulse generated Spiral organ (organ of Corti) Hair cells Basilar membrane (a) (b) Scala vestibuli (contains perilymph) Cochlear duct (contains endolymph) Scala tympani (contains perilymph) Branch of cochlear nerve Tectorial membrane Basilar membrane Supporting cells Nerve fibers Branch of cochlear nerve Vestibular membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

46. 46 Organ of Corti Cochlear duct Scala tympaniHair cells (a) (b) Basilar membrane Tectorial membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © John D. Cunningham/Visuals Unlimited; b: © Fred Hossler/Visuals Unlimited

47. 47 Auditory Nerve Pathways Midbrain Pons Thalamus Auditory cortex (temporal lobe) Medial geniculate body of thalamus Superior olivary nucleus Medulla oblongata Vestibulocochlear nerve Cochlear nuclei Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

48. 48 12.5 Clinical Application Hearing Loss

49. 49 Summary of the Generation of Sensory Impulses from the Ear

50. 50 Sense of Equilibrium Static equilibrium Vestibule Senses position of head when body is not moving Dynamic Equilibrium Semicircular canals Senses rotation and movement of head and body

51. 51 Vestibule Utricle Communicates with saccule and membranous portion of semicircular canals Saccule Communicates with cochlear duct Macula Hair cells of utricle and saccule Saccule Utricle Cochlea Maculae Ampullae of semicircular canals Vestibulocochlear nerve Cochlear duct Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Vestibule

52. Macula Responds to changes in head position Bending of hairs results in generation of nerve impulse Hair cells Sensory (afferent) nerve fiber Supporting cells Otoliths (a) Head upright(b) Head bent forward Macula of utricle Hairs of hair cells bend Gelatinous material sags Gravitational force Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 52

53. 53 Semicircular Canals Three (3) canals at right angles Ampulla Swelling of membranous labyrinth that communicates with the vestibule Crista ampullaris Sensory organ of ampulla Hair cells and supporting cells Rapid turns of head or body stimulate hair cells Saccule Utricle Cochlea Maculae Ampullae of semicircular canals Vestibulocochlear nerve Cochlear duct Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Vestibule

54. 54 Crista Ampullaris Hair cell Supporting cells Sensory (afferent) nerve fibers Hairs Cupula Crista ampullaris (a) Head in still position (b) Head rotating Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (c) Crista ampullaris Semicircular canal Endolymph Ampulla Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

55. 55 Sense of Sight Visual accessory organs Eyelids Lacrimal apparatus Extrinsic eye muscles

56. Eyelid Palpebra Composed of four (4) layers: Skin Muscle Connective tissue Conjunctiva Orbicularis oculi – closes eyelid Levator palpebrae superioris – opens eyelid Tarsal glands – secrete oil onto eyelashes Conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball Eyelash Cornea Conjunctiva Eyelid Tendon of levator palpebrae superioris Superior rectus Orbicularis oculi Inferior rectus Tarsal glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 56

57. Lacrimal Apparatus Lacrimal gland Lateral to eye Secretes tears Canaliculi Collect tears Lacrimal sac Collects from canaliculi Nasolacrimal duct Collects from lacrimal sac Empties tears into nasal cavity Lacrimal gland Lacrimal sac Superior and inferior canaliculi Nasolacrimal duct Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 57

58. Extrinsic Eye Muscles Inferior rectusInferior oblique Medial rectus Superior rectus Superior oblique Lateral rectus (cut) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior rectus Rotates eye up and medially Inferior rectus Rotates eye down and medially Medial rectus Rotates eye medially 58

59. Extrinsic Eye Muscles Inferior rectusInferior oblique Medial rectus Superior rectus Superior oblique Lateral rectus (cut) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral rectus Rotates eye laterally Superior oblique Rotates eye down and laterally Inferior oblique Rotates eye up and laterally 59

60. 60 Structure of the Eye Hollow Spherical Wall has three (3) layers: Outer fibrous tunic Middle vascular tunic Inner nervous tunic Ciliary body Retina Choroid coat Sclera Fovea centralis Optic nerve Lens Iris Pupil Cornea Lateral rectus Medial rectus Optic disc Posterior cavity Vitreous humor Posterior chamber Anterior chamber Aqueous humor Suspensory ligaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior cavity

61. 61 Outer Tunic Ciliary body Retina Choroid coat Sclera Fovea centralis Optic nerve Lens Iris Pupil Cornea Lateral rectus Medial rectus Optic disc Posterior cavity Vitreous humor Posterior chamber Anterior chamber Aqueous humor Suspensory ligaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior cavity Cornea Anterior portion Transparent Light transmission Light refraction Sclera Posterior portion Opaque Protection

62. 62 Middle Tunic Ciliary body Retina Choroid coat Sclera Fovea centralis Optic nerve Lens Iris Pupil Cornea Lateral rectus Medial rectus Optic disc Posterior cavity Vitreous humor Posterior chamber Anterior chamber Aqueous humor Suspensory ligaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior cavity Iris Anterior portion Pigmented Controls light intensity Ciliary body Anterior portion Pigmented Holds lens Moves lens for focusing Choroid coat Provides blood supply Pigments absorb extra light

63. 63 Anterior Portion of Eye Filled with aqueous humor Conjunctiva Iris Lens Ciliary process Ciliary muscles Sclera Cornea Anterior chamber Vitreous humor Suspensory ligaments Posterior chamber Ciliary body Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

64. 64 Lens Conjunctiva Iris Lens Ciliary process Ciliary muscles Sclera Cornea Anterior chamber Vitreous humor Suspensory ligaments Posterior chamber Ciliary body Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Transparent, Biconvex, Lies behind iris, Composed of lens fibers, Elastic, Held in place by suspensory ligaments of ciliary body

65. 65 Ciliary Body Forms internal ring around the front of the eye Ciliary processes – radiating folds Ciliary muscles – contract and relax to move lens Retina Choroid coat Sclera Lens Ciliary processes of ciliary body Suspensory ligaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

66. 66 Accommodation Changing of lens shape to view objects (a) Lens thick Lens thin (b) Ciliary muscle fibers contracted Suspensory ligaments relaxed Ciliary muscle fibers relaxed Suspensory ligaments taut Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

67. 67 Iris Sympathetic motor nerve fiber In dim light Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Radially arranged Smooth muscle fibers of the iris Circularly arranged smooth muscle fibers of the iris Pupil In normal light In bright light Parasympathetic ganglion Parasympathetic motor nerve fiber Composed of connective tissue and smooth muscle Pupil is hole in iris Dim light stimulates radial muscles and pupil dilates Bright light stimulates circular muscles and pupil constricts

68. 68 Aqueous Humor Fluid in anterior cavity of eye Secreted by epithelium on inner surface of the ciliary body Provides nutrients Maintains shape of anterior portion of eye Leaves cavity through Canal of Schlemm Sclera Iris Lens Aqueous humor Cornea Vitreous humor Ciliary process Ciliary muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior chamber Ciliary body Scleral venous sinus (canal of Schlemm) Anterior chamber

69. 69 Inner Tunic Retina Contains visual receptors Continuous with optic nerve Ends just behind margin of the ciliary body Composed of several layers Macula lutea – yellowish spot in retina Fovea centralis – center of macula lutea; produces sharpest vision Optic disc – blind spot; contains no visual receptors Vitreous humor – thick gel that holds retina flat against choroid coat

70. 70 Posterior Cavity Contains vitreous humor – thick gel that holds retina flat against choroid coat Ciliary body Retina Choroid coat Sclera Fovea centralis Optic nerve Lens Iris Pupil Cornea Lateral rectus Medial rectus Optic disc Posterior cavity Vitreous humor Posterior chamber Anterior chamber Aqueous humor Suspensory ligaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior cavity

71. 71 Major Groups of Retinal Neurons Receptor cells, bipolar cells, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve Horizontal cells and amacrine cells – modify impulses Sclera Receptor cells Rod Cone Retina Bipolar neuron Ganglion cell Nerve fibers Horizontal cell Amacrine cell Light waves Retinal pigment epithelium Pigmented choroid coat Impulses to optic nerve Vitreous humor Layer of connecting neurons Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

72. 72 Layers of the Eye

73. 73 Light Refraction Refraction Bending of light Occurs when light waves pass at an oblique angle into mediums of different densities Light wave Perpendicular line Air Glass Refracted light wave Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

74. 74 Types of Lenses Convex lenses cause light waves to converge Concave lenses cause light waves to diverge Air Glass (a)(b) Diverging light waves Convex surface Light wave Converging light waves Concave surface Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

75. 75 Focusing On Retina As light enters eye, it is refracted by: Convex surface of cornea Convex surface of lens Image focused on retina is upside down and reversed from left to right Light waves Object Cornea Image Retina Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

76. 76 Visual Receptors Rods Long, thin projections Contain light sensitive pigment called rhodopsin Hundred times more sensitive to light than cones Provide vision in dim light Produce colorless vision Produce outlines of objects Cones Short, blunt projections Contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe Provide vision in bright light Produce sharp images Produce color vision

77. 77 Rods and Cones Cones Rods Rod Cone (c) Many sensory (afferent) nerve fibers (b) Single sensory (afferent) nerve fiber (a) Retinal pigment epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. c: © Frank S. Werblin, PhD.

78. 78 12.6 Clinical Application Refraction Disorders Concave lens corrects nearsightedness Convex lens corrects farsightedness Light waves Cornea Lens Retina (a) Eye too long (myopia) (b) Normal eye (c) Eye too short (hyperopia) Point of focus Point of focus Point of focus Light waves Concave lens Convex lens (a) (b) Uncorrected point of focus Corrected point of focus Uncorrected point of focus Corrected point of focus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

79. 79 Visual Pigments Rhodopsin Light-sensitive pigment in rods Decomposes in presence of light Triggers a complex series of reactions that initiate nerve impulses Impulses travel along optic nerve Pigments on cones Each set contains different light- sensitive pigment Each set is sensitive to different wavelengths Color perceived depends on which sets of cones are stimulated Erythrolabe – responds to red Chlorolabe – responds to green Cyanolabe – responds to blue

80. 80 Rod Cells Mitochondria Nucleus Discs of membrane within cell Synaptic ending Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

81. 81 Stereoscopic Vision Provides perception of distance and depth Results from formation of two slightly different retinal images Light waves Right eyeLeft eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

82. 82 Visual Nerve Pathway Optic tract Eye Fibers from nasal (medial) half of each retina crossing over Visual cortex of occipital lobe Lateral geniculate body of thalamus Optic chiasma Optic nerve Optic radiations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

83. 83 12.5: Lifespan Changes Age related hearing loss due to: Damage of hair cells in organ of Corti Degeneration of nerve pathways to the brain Tinnitus Age-related visual problems include: Dry eyes Floaters (crystals in vitreous humor) Loss of elasticity of lens Glaucoma Cataracts Macular degeneration

84. 84 Important Points in Chapter 12: Outcomes to be Assessed 12.1: Introduction Explain the difference between general senses and special senses. 12.2: Receptors, Sensation, and Perception Name the five types of receptors and state the function of each. Explain how receptors stimulate sensory impulses. Explain how a sensation is produced. 12.3: General Senses Distinguish between general and special senses. Describe the differences among receptors associated with the senses of touch, pressure, temperature, and pain. Describe how the sensation of pain is produced.

85. 85 Important Points in Chapter 12: Outcomes to be Assessed Explain the importance of stretch receptors in muscles and tendons. 12.4: Special Senses Explain the relationship between the senses of smell and taste. Name the parts of the ear and the function of each part. Distinguish between static and dynamic equilibrium. Name the parts of the eye and the function of each part. Explain how the eye refracts light. Explain how the brain perceives depth and distance. Draw a diagram of the visual nerve pathways.

86. 86 Quiz 12 Complete Quiz 12 now! Read Chapter 13.