1. © 2012 Pearson Education, Inc. PowerPoint ® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris 17 The Special Senses

2. © 2012 Pearson Education, Inc. Figure 17-18 Bleaching and Regeneration of Visual Pigments On absorbing light, retinal changes to a more linear shape. This change activates the opsin molecule. Opsin activation changes the Na  permeability of the outer segment, and this changes the rate of neurotransmitter release by the inner segment at its synapse with a bipolar cell. Na  11-trans retinal Neuro- transmitter release Bipolar cell Changes in bipolar cell activity are detected by one or more ganglion cells. The location of the stimulated ganglion cell indicates the specific portion of the retina stimulated by the arriving photons. Ganglion cell Opsin 11-trans retinal ADP ATP enzyme 11-cis retinal Photon Opsin 11-cis retinal and opsin are reassembled to form rhodopsin. After absorbing a photon, the rhodopsin molecule begins to break down into retinal and opsin, a process known as bleaching. The retinal is converted to its original shape. This conversion requires energy in the form of ATP. Once the retinal has been converted, it can recombine with opsin. The rhodopsin molecule is now ready to repeat the cycle. The regeneration process takes time; after exposure to very bright light, photoreceptors are inactivated while pigment regeneration is under way.

3. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Light and Dark Adaptation Dark Most visual pigments are fully receptive to stimulation Light Pupil constricts Bleaching of visual pigments occurs

4. © 2012 Pearson Education, Inc. 17-4 Visual Physiology The Visual Pathways Begin at photoreceptors End at visual cortex of cerebral hemispheres Message crosses two synapses before it heads toward brain Photoreceptor to bipolar cell Bipolar cell to ganglion cell

5. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Ganglion Cells Monitor a specific portion of a field of vision M Cells Are ganglion cells that monitor rods Are relatively large Provide information about: General form of object Motion Shadows in dim lighting

6. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Ganglion Cells P cells Are ganglion cells that monitor cones Are smaller, more numerous Provide information about edges, fine detail, and color

7. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Ganglion Cells On-center neurons Are excited by light arriving in center of their sensory field Are inhibited when light strikes edges of their receptive field Off-center neurons Inhibited by light in central zone Stimulated by illumination at edges

8. © 2012 Pearson Education, Inc. Figure 17-19 Convergence and Ganglion Cell Function Receptive field of ganglion cell Receptive field Retinal surface (contacts pigment epithelium) Photoreceptors Horizontal cell Bipolar cell Amacrine cell Ganglion cell

9. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Central Processing of Visual Information Axons from ganglion cells converge on optic disc Penetrate wall of eye Proceed toward diencephalon as optic nerve (II) Two optic nerves (one for each eye) reach diencephalon at optic chiasm

10. © 2012 Pearson Education, Inc. 17-4 Visual Physiology Visual Data From combined field of vision arrive at visual cortex of opposite occipital lobe Left half arrive at right occipital lobe Right half arrive at left occipital lobe Optic radiation Bundle of projection fibers linking lateral geniculate with visual cortex

11. © 2012 Pearson Education, Inc. 17-4 Visual Physiology The Field of Vision Depth perception Obtained by comparing relative positions of objects between left-eye and right-eye images

12. © 2012 Pearson Education, Inc. 17-4 Visual Physiology The Brain Stem and Visual Processing Circadian rhythm Is tied to day-night cycle Affects other metabolic processes

13. © 2012 Pearson Education, Inc. Figure 17-20 The Visual Pathways Combined Left side Right side only Right eye only Binocular vision Left eye Retina Optic disc Suprachiasmatic nucleus Diencephalon and brain stem The Visual Pathway Photoreceptors in retina Optic nerve (N II) Optic chiasm Optic tract Lateral geniculate nucleus Superior colliculus Right cerebral hemisphere Left cerebral hemisphere Projection fibers (optic radiation) Visual cortex of cerebral hemispheres Visual Field

14. © 2012 Pearson Education, Inc. 17-5 The Ear The External Ear Auricle Surrounds entrance to external acoustic meatus Protects opening of canal Provides directional sensitivity

15. © 2012 Pearson Education, Inc. 17-5 The Ear The External Ear External acoustic meatus Ends at tympanic membrane (eardrum) Tympanic membrane Is a thin, semitransparent sheet Separates external ear from middle ear

16. © 2012 Pearson Education, Inc. Figure 17-21 The Anatomy of the Ear External Ear Elastic cartilages Auricle External acoustic meatus Tympanic membrane Tympanic cavity Middle Ear Auditory ossicles Oval window Semicircular canals Petrous part of temporal bone Facial nerve (N VII) Cochlea Vestibulocochlear nerve (N VIII) Bony labyrinth of internal ear Auditory tube To nasopharynx Vestibule Round window Internal Ear

17. © 2012 Pearson Education, Inc. 17-5 The Ear The External Ear Ceruminous glands Integumentary glands along external acoustic meatus Secrete waxy material (cerumen) Keeps foreign objects out of tympanic membrane Slows growth of microorganisms in external acoustic meatus

18. © 2012 Pearson Education, Inc. 17-5 The Ear The Middle Ear Also called tympanic cavity Communicates with nasopharynx via auditory tube Permits equalization of pressures on either side of tympanic membrane Encloses and protects three auditory ossicles 1.Malleus (hammer) 2.Incus (anvil) 3.Stapes (stirrup)

19. © 2012 Pearson Education, Inc. Figure 17-22a The Middle Ear Temporal bone (petrous part) Malleus IncusStapes Oval window Muscles of the Middle Ear Tensor tympani muscle Stapedius muscle Round window Auditory tube Stabilizing ligaments Branch of facial nerve VII (cut) External acoustic meatus Tympanic cavity (middle ear) Tympanic membrane The structures of the middle ear. Auditory Ossicles

20. © 2012 Pearson Education, Inc. Figure 17-22b The Middle Ear Tendon of tensor tympani muscle Malleus Malleus attached to tympanic membrane Incus Base of stapes at oval window Stapes Stapedius muscle Inner surface of tympanic membrane The tympanic membrane and auditory ossicles

21. © 2012 Pearson Education, Inc. 17-5 The Ear Vibration of Tympanic Membrane Converts arriving sound waves into mechanical movements Auditory ossicles conduct vibrations to inner ear Tensor tympani muscle Stiffens tympanic membrane Stapedius muscle Reduces movement of stapes at oval window

22. © 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Contains fluid called endolymph Bony labyrinth surrounds and protects membranous labyrinth Subdivided into: Vestibule Semicircular canals Cochlea

23. © 2012 Pearson Education, Inc. Figure 17-23b The Internal Ear Semicircular ducts Anterior Lateral Posterior Semicircular canal Utricle Saccule Vestibular duct Cochlear duct Vestibule Cristae within ampullae Maculae Endolymphatic sac Membranous labyrinth Bony labyrinth KEY Cochlea Spiral organ Tympanic duct The bony and membranous labyrinths. Areas of the membranous labyrinth containing sensory receptors (cristae, maculae, and spiral organ) are shown in purple.

24. © 2012 Pearson Education, Inc. Figure 17-23a The Internal Ear Perilymph Bony labyrinth Endolymph Membranous labyrinth A section through one of the semicircular canals, showing the relationship between the bony and membranous labyrinths, and the boundaries of perilymph and endolymph. Membranous labyrinth Bony labyrinth KEY

25. © 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Vestibule Encloses saccule and utricle Receptors provide sensations of gravity and linear acceleration Semicircular canals Contain semicircular ducts Receptors stimulated by rotation of head

26. © 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Cochlea Contains cochlear duct (elongated portion of membranous labyrinth) Receptors provide sense of hearing

27. © 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Round window Thin, membranous partition Separates perilymph from air spaces of middle ear Oval window Formed of collagen fibers Connected to base of stapes

28. © 2012 Pearson Education, Inc. 17-5 The Ear Stimuli and Location Sense of gravity and acceleration From hair cells in vestibule Sense of rotation From semicircular canals Sense of sound From cochlea

29. © 2012 Pearson Education, Inc. 17-5 The Ear Equilibrium Sensations provided by receptors of vestibular complex Hair cells Basic receptors of inner ear Provide information about direction and strength of mechanical stimuli

30. © 2012 Pearson Education, Inc. 17-5 The Ear The Semicircular Ducts Are continuous with utricle Each duct contains: Ampulla with gelatinous cupula Associated sensory receptors Stereocilia – resemble long microvilli Are on surface of hair cell Kinocilium – single large cilium

31. © 2012 Pearson Education, Inc. Figure 17-24a The Semicircular Ducts Semicircular ducts Anterior Lateral Posterior Ampulla Utricle Saccule Maculae Vestibular branch (N VIII) Cochlea Endolymphatic sac Endolymphatic duct An anterior view of the right semicircular ducts, the utricle, and the saccule, showing the locations of sensory receptors

32. © 2012 Pearson Education, Inc. Figure 17-24b The Semicircular Ducts Cupula A cross section through the ampulla of a semicircular duct Crista Supporting cells Sensory nerve Ampulla filled with endolymph Hair cells

33. © 2012 Pearson Education, Inc. Figure 17-24c The Semicircular Ducts Endolymph movement along the length of the duct moves the cupula and stimulates the hair cells. At rest Direction of duct rotation Direction of relative endolymph movement Semicircular duct Direction of duct rotation Ampulla

34. © 2012 Pearson Education, Inc. Figure 17-24d The Semicircular Ducts Stereocilia Kinocilium Hair cell Sensory nerve ending Supporting cell A representative hair cell (receptor) from the vestibular complex. Bending the sterocilia toward the kinocilium depolarizes the cell and stimulates the sensory neuron. Displacement in the opposite direction inhibits the sensory neuron. Displacement in this direction inhibits hair cell Displacement in this direction stimulates hair cell

35. © 2012 Pearson Education, Inc. 17-5 The Ear The Utricle and Saccule Provide equilibrium sensations Are connected with the endolymphatic duct, which ends in endolymphatic sac

36. © 2012 Pearson Education, Inc. 17-5 The Ear The Utricle and Saccule Maculae Oval structures where hair cells cluster Statoconia Densely packed calcium carbonate crystals on surface of gelatinous mass Otolith (ear stone) = gelatinous matrix and statoconia

37. © 2012 Pearson Education, Inc. Figure 17-25ab The Saccule and Utricle The location of the maculae Otolith Nerve fibers Hair cells Statoconia Gelatinous material The structure of an individual macula

38. © 2012 Pearson Education, Inc. Figure 17-25c The Saccule and Utricle Head in normal, upright position Gravity Head tilted posteriorly Receptor output increases Otolith moves “downhill,” distorting hair cell processes A diagrammatic view of macular function when the head is held horizontally and then tilted back 21

39. © 2012 Pearson Education, Inc. 17-5 The Ear Pathways for Equilibrium Sensations Vestibular receptors Activate sensory neurons of vestibular ganglia Axons form vestibular branch of vestibulocochlear nerve (VIII) Synapse within vestibular nuclei

40. © 2012 Pearson Education, Inc. 17-5 The Ear Four Functions of Vestibular Nuclei 1.Integrate sensory information about balance and equilibrium from both sides of head 2.Relay information from vestibular complex to cerebellum 3.Relay information from vestibular complex to cerebral cortex Provide conscious sense of head position and movement 4.Send commands to motor nuclei in brain stem and spinal cord

41. © 2012 Pearson Education, Inc. Figure 17-26 Pathways for Equilibrium Sensations Vestibular ganglion Vestibular branch Red nucleus Semicircular canals Vestibule Cochlear branch N VI N IV N III Vestibular nucleus N XI Vestibulocochlear nerve (N VIII) To cerebellum Vestibulospinal tracts To superior colliculus and relay to cerebral cortex

42. © 2012 Pearson Education, Inc. 17-5 The Ear Eye, Head, and Neck Movements Reflexive motor commands From vestibular nuclei Distributed to motor nuclei for cranial nerves Peripheral Muscle Tone, Head, and Neck Movements Instructions descend in vestibulospinal tracts of spinal cord

43. © 2012 Pearson Education, Inc. 17-5 The Ear Eye Movements Sensations of motion directed by superior colliculi of the midbrain Attempt to keep focus on specific point If spinning rapidly, eye jumps from point to point Nystagmus Have trouble controlling eye movements Caused by damage to brain stem or inner ear

44. © 2012 Pearson Education, Inc. 17-5 The Ear Hearing Cochlear duct receptors Provide sense of hearing

45. © 2012 Pearson Education, Inc. Figure 17-27a The Cochlea Scala vestibuli Cochlear duct Scala tympani Round window Stapes at oval window Cochlear branch Vestibular branch Vestibulocochlear nerve (N VIII) The structure of the cochlea KEY From oval window to tip of spiral From tip of spiral to round window Semicircular canals

46. © 2012 Pearson Education, Inc. Figure 17-27b The Cochlea Vestibular membrane Tectorial membrane Basilar membrane From oval window To round window Temporal bone (petrous part) Scala vestibuli (contains perilymph) Cochlear duct (contains endolymph) Spiral organ Spiral ganglion Scala tympani (contains perilymph) Cochlear nerve Vestibulocochlear nerve (N VIII) Diagrammatic and sectional views of the cochlear spiral

47. © 2012 Pearson Education, Inc. Figure 17-27b The Cochlea Diagrammatic and sectional views of the cochlear spiral Temporal bone (petrous part) Scala vestibuli (contains perilymph) Cochlear duct (contains endolymph) Spiral organ Spiral ganglion Scala tympani (contains perilymph) Cochlear spiral section LM  60 Vestibular membrane Basilar membrane Cochlear nerve

48. © 2012 Pearson Education, Inc. 17-5 The Ear Hearing Auditory ossicles Convert pressure fluctuation in air into much greater pressure fluctuations in perilymph of cochlea Frequency of sound Determined by which part of cochlear duct is stimulated Intensity (volume) Determined by number of hair cells stimulated

49. © 2012 Pearson Education, Inc. 17-5 The Ear Hearing Cochlear duct receptors Basilar membrane Separates cochlear duct from tympanic duct Hair cells lack kinocilia Stereocilia in contact with overlying tectorial membrane

50. © 2012 Pearson Education, Inc. Figure 17-28a The Spiral Organ A three-dimensional section of the cochlea, showing the compartments, tectorial membrane, and spiral organ Cochlear branch of N VIII Spiral ganglion Body cochlear wall Scala vestibuli Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Scala tympani Spiral organ

51. © 2012 Pearson Education, Inc. Figure 17-28b The Spiral Organ Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ

52. © 2012 Pearson Education, Inc. Figure 17-28b The Spiral Organ Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ Spiral organ Cochlear duct (scala media) Basilar membrane Hair cells of spiral organ Spiral ganglion cells of cochlear nerve LM  125 Vestibular membrane Tectorial membrane Scala tympani

53. © 2012 Pearson Education, Inc. 17-5 The Ear An Introduction to Sound Pressure Waves Consist of regions where air molecules are crowded together Adjacent zone where molecules are farther apart Sine waves S-shaped curves

54. © 2012 Pearson Education, Inc. 17-5 The Ear Pressure Wave Wavelength Distance between two adjacent wave troughs Frequency Number of waves that pass fixed reference point at given time Physicists use term cycles instead of waves Hertz (Hz) number of cycles per second (cps)

55. © 2012 Pearson Education, Inc. 17-5 The Ear Pressure Wave Pitch Our sensory response to frequency Amplitude Intensity of sound wave Sound energy is reported in decibels

56. © 2012 Pearson Education, Inc. Figure 17-29a The Nature of Sound Wavelength Tuning fork Air molecules Tympanic membrane Sound waves (here, generated by a tuning fork) travel through the air as pressure waves.

57. © 2012 Pearson Education, Inc. Figure 17-29b The Nature of Sound A graph showing the sound energy arriving at the tympanic membrane. The distance between wave peaks is the wavelength. The number of waves arriving each second is the frequency, which we perceive as pitch. Frequencies are reported in cycles per second (cps), or hertz (Hz). The amount of energy in each wave determines the wave’s amplitude, or intensity, which we perceive as the loudness of the sound. 1 wavelength Amplitude

58. © 2012 Pearson Education, Inc. Figure 17-31a Frequency Discrimination Stapes at oval window Round window 16,000 Hz Basilar membrane Cochlea 6000 Hz1000 Hz The flexibility of the basilar membrane varies along its length, so pressure waves of different frequencies affect different parts of the membrane.

59. © 2012 Pearson Education, Inc. Figure 17-31b Frequency Discrimination Stapes moves inward Round window pushed outward Basilar membrane distorts toward round window The effects of a vibration of the stapes at a frequency of 6000 Hz. When the stapes moves inward, as shown here, the basilar membrane distorts toward the round window, which bulges into the middle-ear cavity.

60. © 2012 Pearson Education, Inc. Figure 17-31c Frequency Discrimination Stapes moves outward Round window pulled inward Basilar membrane distorts toward oval window When the stapes moves outward, as shown here, the basilar membrane rebounds and distorts toward the oval window.

61. © 2012 Pearson Education, Inc. Figure 17-30 Sound and Hearing External acoustic meatus Malleus Incus Movement of sound waves Tympanic membrane Round window Stapes Oval window Sound waves arrive at tympanic membrane. Movement of the tympanic membrane causes displacement of the auditory ossicles. Movement of the stapes at the oval window establishes pressure waves in the perilymph of the scala vestibuli.

62. © 2012 Pearson Education, Inc. Figure 17-30 Sound and Hearing Cochlear branch of cranial nerve VIII Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Scala tympani (contains perilymph) The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane. Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII. Basilar membrane

63. © 2012 Pearson Education, Inc. 17-5 The Ear Auditory Pathways Cochlear branch Formed by afferent fibers of spiral ganglion neurons Enters medulla oblongata Synapses at dorsal and ventral cochlear nuclei Information crosses to opposite side of brain Ascends to inferior colliculus of midbrain

64. © 2012 Pearson Education, Inc. 17-5 The Ear Auditory Pathways Ascending auditory sensations Synapse in medial geniculate nucleus of thalamus Projection fibers deliver information to auditory cortex of temporal lobe

65. © 2012 Pearson Education, Inc. Figure 17-32 Pathways for Auditory Sensations Stimulation of hair cells at a specific location along the basilar membrane activates sensory neurons. Cochlea Low-frequency sounds High-frequency sounds Vestibular branch KEY Sensory neurons carry the sound information in the cochlear branch of the vestibulocochlear nerve (VIII) to the cochlear nucleus on that side. Primary pathway Secondary pathway Motor output Vestibulocochlear nerve (VIII)

66. © 2012 Pearson Education, Inc. Figure 17-32 Pathways for Auditory Sensations KEY Primary pathway Secondary pathway Motor output Motor output to spinal cord through the tectospinal tracts To reticular formation and motor nuclei of cranial nerves Information ascends from each cochlear nucleus to the inferior colliculi of the midbrain. The inferior colliculi direct a variety of unconscious motor responses to sounds. Ascending acoustic information goes to the medial geniculate nucleus. Low-frequency sounds High- frequency sounds Thalamus Projection fibers then deliver the information to specific locations within the auditory cortex of the temporal lobe. To cerebellum

67. © 2012 Pearson Education, Inc. 17-5 The Ear Hearing Range From softest to loudest represents trillionfold increase in power Never use full potential Young children have greatest range

68. © 2012 Pearson Education, Inc. Table 17-1 Intensity of Representative Sounds

69. © 2012 Pearson Education, Inc. 17-5 The Ear Effects of Aging on the Ear With age, damage accumulates Tympanic membrane gets less flexible Articulations between ossicles stiffen Round window may begin to ossify