AMiNeS by john18 lecture presentation
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The document provides an overview of the nervous system's general and special senses. It discusses how sensory information is detected by receptors and transmitted to the central nervous system via sensory neurons. The general senses of touch, pain, temperature, and proprioception are mediated by free nerve endings and specialized receptors. The special senses of smell, taste, hearing, vision, and balance also have unique sensory receptor cells and pathways for transmitting information to the brain. In summary, the document covers the key receptors, pathways, and neural processing involved in the senses.
AMiNeS by john18 lecture presentation
- 1. © 2012 Pearson Education, Inc. 18 The Nervous System: General and Special Senses PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska
- 2. © 2012 Pearson Education, Inc. Introduction • Sensory information arrives at the CNS • Information is “picked up” by sensory receptors • Sensory receptors are the interface between the nervous system and the internal and external environment • General senses • Refers to temperature, pain, touch, pressure, vibration, and proprioception • Special senses • Refers to smell, taste, balance, hearing, and vision
- 3. © 2012 Pearson Education, Inc. Receptors • Receptors and Receptive Fields • Free nerve endings are the simplest receptors • These respond to a variety of stimuli • Receptors of the retina (for example) are very specific and only respond to light • Receptive fields • Large receptive fields have receptors spread far apart, which makes it difficult to localize a stimulus • Small receptive fields have receptors close together, which makes it easy to localize a stimulus.
- 4. © 2012 Pearson Education, Inc. Figure 18.1 Receptors and Receptive Fields Receptive fields Receptive field 1 Receptive field 2
- 5. © 2012 Pearson Education, Inc. Receptors • Interpretation of Sensory Information • Information is relayed from the receptor to a specific neuron in the CNS • The connection between a receptor and a neuron is called a labeled line • Each labeled line transmits its own specific sensation
- 6. © 2012 Pearson Education, Inc. Interpretation of Sensory Information • Classification of Receptors • Tonic receptors • Always active • Photoreceptors of the eye constantly monitor body position • Phasic receptors • Normally inactive but become active when necessary (for short periods of time) • Touch and pressure receptors of the skin (for example)
- 7. © 2012 Pearson Education, Inc. Receptors • Central Processing and Adaptation • Adaptation • Reduction in sensitivity due to a constant stimulus • Peripheral adaptation • Receptors respond strongly at first and then decline • Central adaptation • Adaptation within the CNS • Consciously aware of a stimulus, which quickly disappears
- 8. © 2012 Pearson Education, Inc. The General Senses • Classification of the General Senses • One classification scheme: • Exteroceptors: provide information about the external environment • Proprioceptors: provide information about the position of the body • Interoceptors: provide information about the inside of the body
- 9. © 2012 Pearson Education, Inc. The General Senses • Classification of the General Senses • Another classification scheme: • Nociceptors: respond to the sensation of pain • Thermoreceptors: respond to changes in temperature • Mechanoreceptors: activated by physical distortion of cell membranes • Chemoreceptors: monitor the chemical composition of body fluids
- 10. © 2012 Pearson Education, Inc. The General Senses • Nociceptors • Known as pain receptors • Associated with free nerve endings and large receptor fields. This makes it difficult to “pinpoint” the location of the origin of the pain • Three types • Receptors sensitive to extreme temperatures • Receptors sensitive to mechanical damage • Receptors sensitive to chemicals
- 11. © 2012 Pearson Education, Inc. The General Senses • Nociceptors • Fast pain: • Sensations reach the CNS fast • Associated with pricking pain or cuts • Slow pain: • Sensations reach the CNS slowly • Associated with burns or aching pains • Referred pain: • Sensations reach the spinal cord via the dorsal roots • Some visceral organ pain sensations may reach the spinal cord via the same dorsal root
- 12. © 2012 Pearson Education, Inc. Figure 18.2 Referred Pain Heart Liver and gallbladder Stomach Small intestine Appendix Colon Ureters
- 13. © 2012 Pearson Education, Inc. The General Senses • Thermoreceptors • Found in the dermis, skeletal muscles, liver, and hypothalamus • Cold receptors are more numerous than hot receptors • Exist as free nerve endings • These are phasic receptors • Information is transmitted along the same pathway as pain information
- 14. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Receptors that are sensitive to stretch, compression, twisting, or distortion of the plasmalemmae • There are three types • Tactile receptors • Baroreceptors • Proprioceptors
- 15. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Tactile receptors • Provide sensations of touch, pressure, and vibrations • Unencapsulated tactile receptors: free nerve endings, tactile disc, and root hair plexus • Encapsulated tactile receptors: tactile corpuscle, Ruffini corpuscle, and lamellated corpuscle
- 16. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Unencapsulated tactile receptors • Free nerve endings are common in the dermis • Tactile discs are in the stratum basale layer • Root hair plexus monitors distortions and movements of the body surface
- 17. © 2012 Pearson Education, Inc. Figure 18.3a Tactile Receptors in the Skin Free nerve endings Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 18. © 2012 Pearson Education, Inc. Figure 18.3b Tactile Receptors in the Skin Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves Merkel cells Tactile disc Merkel cells and tactile discs
- 19. © 2012 Pearson Education, Inc. Figure 18.3c Tactile Receptors in the Skin Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves Free nerve endings of root hair plexus
- 20. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Encapsulated tactile receptors • Tactile corpuscle: common on eyelids, lips, fingertips, nipples, and genitalia • Ruffini corpuscle: in the dermis, sensitive to pressure and distortion • Lamellated corpuscle: consists of concentric cellular layers / sensitive to vibrations
- 21. © 2012 Pearson Education, Inc. Figure 18.3d Tactile Receptors in the Skin Tactile corpuscle; the capsule boundary in the micrograph is indicated by a dashed line. Tactile corpuscle Epidermis Dermis Tactile corpuscle LM 550 Capsule Accessory cells Dendrites Sensory nerve fiber Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 22. © 2012 Pearson Education, Inc. Figure 18.3e Tactile Receptors in the Skin Capsule Dendrites Ruffini corpuscle Sensory nerve fiber Collagen fibers Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 23. © 2012 Pearson Education, Inc. Figure 18.3f Tactile Receptors in the Skin Lamellated corpuscle Dendritic process Concentric layers (lamellae) of collagen fibers separated by fluid Concentric layers (lamellae) of collagen fibers separated by fluid Accessory cells (specialized fibrocytes) Dendritic process Dermis LM 125Lamellated corpuscle Hair Root hair plexus Lamellated corpuscle Ruffini corpuscle Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 24. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Baroreceptors • Stretch receptors that monitor changes in the stretch of organs • Found in the stomach, small intestine, urinary bladder, carotid artery, lungs, and large intestine
- 25. © 2012 Pearson Education, Inc. Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions Provide information on volume of tract segments, trigger reflex movement of materials along tract Provide information on volume of urinary bladder, trigger urinary reflex Baroreceptors of Bladder Wall Baroreceptors of Digestive Tract Baroreceptors of Carotid Sinus and Aortic Sinus Baroreceptors of Lung Baroreceptors of Colon Provide information on blood pressure to cardiovascular and respiratory control centers Provide information on lung stretching to respiratory rhythmicity centers for control of respiratory rate Provide information on volume of fecal material in colon, trigger defecation reflex
- 26. © 2012 Pearson Education, Inc. The General Senses • Mechanoreceptors • Proprioceptors • Monitor the position of joints, tension in the tendons and ligaments, and the length of muscle fibers upon contraction • Muscle spindles are receptors in the muscles • Golgi tendon organs are the receptors in the tendons
- 27. © 2012 Pearson Education, Inc. The General Senses • Chemoreceptors • Detect small changes in the concentration of chemicals • Respond to water-soluble or lipid-soluble compounds • Found in respiratory centers of the medulla oblongata, carotid arteries, and aortic arch
- 28. © 2012 Pearson Education, Inc. Figure 18.5 Chemoreceptors Carotid body LM 1500 Blood vessel Chemoreceptive neurons Trigger reflexive adjustments in depth and rate of respiration Trigger reflexive adjustments in respiratory and cardiovascular activity Via cranial nerve IX Via cranial nerve X Sensitive to changes in pH and PCO2 in cerebrospinal fluid Sensitive to changes in pH, PCO2 , and PO2 in blood Sensitive to changes in pH, PCO2 , and PO2 in blood Chemoreceptors in and near Respiratory Centers of Medulla Oblongata Chemoreceptors of Carotid Bodies Chemoreceptors of Aortic Bodies
- 29. © 2012 Pearson Education, Inc. The Special Senses • The special senses include: • Olfaction (smell) • Gustation (taste) • Equilibrium • Hearing • Vision
- 30. © 2012 Pearson Education, Inc. Olfaction (Smell) • Olfaction • The olfactory epithelium consists of: • Olfactory receptors • Supporting cells • Basal cells
- 31. © 2012 Pearson Education, Inc. Olfaction (Smell) • Olfactory Pathways • Axons leave the olfactory epithelium • Pass through the cribriform foramina • Synapse on neurons in the olfactory bulbs • Impulses travel to the brain via CN I • Arrive at the cerebral cortex, hypothalamus, and limbic system
- 32. © 2012 Pearson Education, Inc. Figure 18.6a The Olfactory Organs The distribution of the olfactory receptors on the left side of the nasal septum is shown by the shading. Olfactory bulb Olfactory nerve fibers (N I) Olfactory tract Cribriform plate of ethmoid Olfactory epithelium
- 33. © 2012 Pearson Education, Inc. Figure 18.6b The Olfactory Organs A detailed view of the olfactory epithelium Substance being smelled Olfactory epithelium Lamina propria Cribriform plate Knob Olfactory cilia: surfaces contain receptor proteins Mucous layer Supporting cell Olfactory receptor cell Developing olfactory receptor cell Olfactory nerve fibers To olfactory bulb Olfactory (Bowman’s) gland Regenerative basal cell: divides to replace worn-out olfactory receptor cells
- 34. © 2012 Pearson Education, Inc. Olfaction (Smell) • Olfactory Discrimination • The epithelial receptors have different sensitivities and we therefore “detect” different smells • Olfactory receptors can be replaced • The replacement activity declines with age
- 35. © 2012 Pearson Education, Inc. Gustation (Taste) • Gustation • The tongue consists of papillae • Papillae consist of taste buds • Taste buds consist of gustatory cells • Each gustatory cell has a slender microvilli that extends through the taste pore into the surrounding fluid
- 36. © 2012 Pearson Education, Inc. Gustation (Taste) • Gustation Pathways • Dissolved chemicals contact the taste hairs (microvilli) • Impulses go from the gustatory cell through CN VII, IX, and X • Synapse in the nucleus solitarius of the medulla oblongata • The impulses eventually arrive at the cerebral cortex
- 37. © 2012 Pearson Education, Inc. Figure 18.8 Gustatory Pathways Gustatory cortex Thalamic nucleus Medial lemniscus Nucleus solitarius Vagus nerve (N X) Facial nerve (N VII) Glossopharyngeal nerve (N IX)
- 38. © 2012 Pearson Education, Inc. Gustation (Taste) • Gustation Discrimination • We begin life with more than 10,000 taste buds • The number declines rapidly by age 50 • Threshold level is low for gustatory cells responsible for unpleasant stimuli • Threshold level is high for gustatory cells responsible for pleasant stimuli
- 39. © 2012 Pearson Education, Inc. Equilibrium and Hearing • Equilibrium and Hearing • Structures of the ear are involved in balance and hearing • The ear is subdivided into three regions • External ear • Middle ear • Inner ear ANIMATION The Ear: Ear Anatomy
- 40. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The External Ear • Consists of: • Auricle • External acoustic meatus • Tympanic membrane • Ceruminous glands
- 41. © 2012 Pearson Education, Inc. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea To nasopharynx Bony labyrinth of inner ear Vestibulocochlear nerve (N VIII)
- 42. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Middle Ear • Consists of: • Tympanic cavity • Auditory ossicles • Malleus, incus, and stapes • Auditory tube (pharyngotympanic tube)
- 43. © 2012 Pearson Education, Inc. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea To nasopharynx Bony labyrinth of inner ear Vestibulocochlear nerve (N VIII)
- 44. © 2012 Pearson Education, Inc. Figure 18.10a The Middle Ear Inferior view of the right temporal bone drawn, as if transparent, to show the location of the middle and inner ear Inner ear Tympanic cavity (middle ear) External acoustic meatus Tympanic membrane Auditory ossicles Auditory tube
- 45. © 2012 Pearson Education, Inc. Figure 18.10b The Middle Ear Structures within the middle ear cavity Temporal bone (petrous part) Stabilizing ligament Chorda tympani nerve (cut), a branch of N VII External acoustic meatus Tympanic cavity (middle ear) Tympanic membrane (tympanum) Malleus Incus Base of stapes at oval window Tensor tympani muscle Stapes Round window Stapedius muscle Auditory tube
- 46. © 2012 Pearson Education, Inc. Figure 18.10c The Middle Ear The isolated auditory ossicles Malleus Incus Points of attachment to tympanic membrane Stapes Base of stapes
- 47. © 2012 Pearson Education, Inc. Figure 18.10d The Middle Ear The tympanic membrane and auditory ossicles as seen through a fiber-optic tube inserted along the auditory canal and into the middle ear cavity Incus Base of stapes at oval window Stapes Stapedius muscle Malleus Tendon of tensor tympani muscle Malleus attached to tympanic membrane Inner surface of tympanic membrane
- 48. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Inner Ear • Consists of: • Receptors • Membranous labyrinth (within the bony labyrinth) • Bony labyrinth • Vestibule • Semicircular canals • Cochlea • Utricle • Saccule
- 49. © 2012 Pearson Education, Inc. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea To nasopharynx Bony labyrinth of inner ear Vestibulocochlear nerve (N VIII)
- 50. © 2012 Pearson Education, Inc. Figure 18.12a Semicircular Canals and Ducts Anterior view of the bony labyrinth cut away to show the semicircular canals and the enclosed semicircular ducts of the membranous labyrinth Cochlear duct Vestibular duct Saccule Utricle Tympanic duct Organ of Corti Cochlea Endolymphatic sac Maculae Cristae within ampullae Bony labyrinth Membranous labyrinth KEY Vestibule Anterior Lateral Posterior Semicircular canal Semicircular ducts
- 51. © 2012 Pearson Education, Inc. Figure 18.12b Semicircular Canals and Ducts Cross section of a semicircular canal to show the orientation of the bony labyrinth, perilymph, membranous labyrinth, and endolymph Perilymph Bony labyrinth Endolymph Membranous labyrinth
- 52. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Inner Ear • The vestibular complex and equilibrium • Part of inner ear that provides equilibrium sensations by detecting rotation, gravity, and acceleration • Consists of: • Semicircular canals • Utricle • Saccule
- 53. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Vestibular Complex and Equilibrium • The semicircular canals • Each semicircular canal encases a duct • The beginning of each duct is the ampulla • Within each ampulla is a cristae with hair cells • Each hair cell contains a kinocilium and stereocilia • These are embedded in gelatinous material called the cupula • The movement of the body causes movement of fluid in the canal, which in turn causes movement of the cupula and hair cells, which the brain detects
- 54. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Vestibular Complex and Equilibrium • The utricle and saccule • The utricle and saccule are connected to the ampulla and to each other and to the fluid within the cochlea • Hair cells of the utricle and saccule are in clusters called maculae • Hair cells are embedded in gelatinous material consisting of statoconia (calcium carbonate crystals) • Gelatinous material and statoconia collectively are called an otolith ANIMATION The Ear: Ear Balance
- 55. © 2012 Pearson Education, Inc. Equilibrium and Hearing • Equilibrium Process • When you rotate your head: • The endolymph in the semicircular canals begins to move • This causes the bending of the kinocilium and stereocilia • This bending causes depolarization of the associated sensory nerve • When you rotate your head to the right, the hair cells are bending to the left (due to movement of the endolymph) • When you move in a circle and then stop abruptly, the endolymph moves back and forth causing the hair cells to bend back and forth resulting in confusing signals, thus dizziness
- 56. © 2012 Pearson Education, Inc. Figure 18.13 The Function of the Semicircular Ducts, Part I Anterior view of the maculae and semicircular ducts of the right side A section through the ampulla of a semicircular duct Endolymph movement along the length of the duct moves the cupula and stimulates the hair cells. Structure of a typical hair cell showing details revealed by electron microscopy. Bending the stereocilia toward the kinocilium depolarizes the cell and stimulates the sensory neuron. Displacement in the opposite direction inhibits the sensory neuron. Supporting cell Sensory nerve ending Hair cell StereociliaKinocilium Displacement in this direction inhibits hair cell Displacement in this direction stimulates hair cell At rest Ampulla Semicircular duct Direction of duct rotation Direction of relative endolymph movement Direction of duct rotation Crista Hair cells Ampulla filled with endolymph Cupula Supporting cells Sensory nerve Saccule Maculae Utricle AmpullaAnterior Posterior Lateral Semicircular ducts Vestibular branch (N VIII) Cochlea Endolymphatic sac Endolymphatic duct
- 57. © 2012 Pearson Education, Inc. Figure 18.14 The Function of the Semicircular Ducts, Part II Location and orientation of the membranous labyrinth within the petrous parts of the temporal bones A superior view showing the planes of sensitivity for the semicircular ducts Posterior semicircular duct for ―tilting head‖ Lateral semicircular duct for ―no‖ Anterior semicircular duct for ―yes‖
- 58. © 2012 Pearson Education, Inc. Equilibrium and Hearing • Equilibrium Process (cont.) • When you move up or down (elevator movement): • Otoliths rest on top of the maculae • When moving upward, the otoliths press down on the macular surface • When moving downward, the otoliths lift off the macular surface • When you tilt side to side: • When tilting to one side, the otoliths shift to one side of the macular surface
- 59. © 2012 Pearson Education, Inc. Figure 18.15ab The Maculae of the Vestibule A scanning electron micrograph showing the crystalline structure of otoliths Detailed structure of a sensory macula Otolith Gelatinous material Statoconia Hair cells Nerve fibers Statoconia Otolith
- 60. © 2012 Pearson Education, Inc. Figure 18.15c The Maculae of the Vestibule Diagrammatic view of changes in otolith position during tilting of the head Head in Neutral Position Head Tilted Posteriorly Gravity Gravity Receptor output increases Otolith moves ―downhill,‖ distorting hair cell processes
- 61. © 2012 Pearson Education, Inc. Figure 18.16 Neural Pathways for Equilibrium Sensations Semicircular canals Vestibular ganglion Vestibular branch Vestibule Cochlear branch Vestibulocochlear nerve (N VIII) Vestibulospinal tracts To cerebellum Vestibular nucleus To superior colliculus and relay to cerebral cortex Red nucleus N III N IV N VI N XI
- 62. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Cochlea • Consists of “snail-shaped” spirals • Spirals coil around a central area called the modiolus • Within the modiolus are sensory neurons • The sensory neurons are associated with CN VIII • Organ of Corti
- 63. © 2012 Pearson Education, Inc. Figure 18.17ab The Cochlea and Organ of Corti Structure of the cochlea within the temporal bone showing the turns of the vestibular duct, cochlear duct, and tympanic duct Structure of the cochlea in partial section KEY From tip of spiral to round window From oval window to tip of spiral Round window Stapes at oval window Semicircular canals Vestibulocochlear nerve (VIII) Cochlear branch Vestibular branch Tympanic duct Vestibular duct Cochlear duct Apical turn Spiral ganglion Modiolus Vestibular membrane Tectorial membrane Basilar membrane Middle turn Vestibular duct (scala vestibuli—contains perilymph) Organ of Corti Cochlear duct (scala media—contains endolymph) Tympanic duct (scala tympani—contains perilymph) Basal turn Temporal bone (petrous part) Cochlear nerve Vestibulocochlear nerve (VIII) From oval window To round window
- 64. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Cochlea (cont.) • Each spiral consists of three layers • Scala vestibuli (vestibular duct): consists of perilymph • Scala tympani (tympanic duct): consists of perilymph • Scala media (cochlear duct): consists of endolymph / this layer is between the scala vestibuli and scala tympani • There is a basilar membrane between each layer • The scala vestibuli and scala tympani are connected at the apical end of the cochlea • Sense organs rest on the basilar membrane within the scala media
- 65. © 2012 Pearson Education, Inc. Equilibrium and Hearing • The Cochlea • The Organ of Corti • Also known as the spiral organ • Rests on the basilar membrane between the scala media and the scala tympani • Hair cells are in contact with an overlying tectorial membrane • This membrane is attached to the lining of the scala media • Sound waves ultimately cause a distortion of the tectorial membrane, thus stimulating the organ of Corti
- 66. © 2012 Pearson Education, Inc. Equilibrium and Hearing • Auditory Pathways • Sound waves enter the external acoustic meatus • The tympanic membrane vibrates • Causes the vibration of the ossicles • The stapes vibrates against the oval window of the scala tympani • Perilymph begins to move
- 67. © 2012 Pearson Education, Inc. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea To nasopharynx Bony labyrinth of inner ear Vestibulocochlear nerve (N VIII)
- 68. © 2012 Pearson Education, Inc. Figure 18.17a–c The Cochlea and Organ of Corti Structure of the cochlea within the temporal bone showing the turns of the vestibular duct, cochlear duct, and tympanic duct Structure of the cochlea in partial section Histology of the cochlea showing many of the structures in part (b) KEY From tip of spiral to round window From oval window to tip of spiral Round window Stapes at oval window Semicircular canals Vestibulocochlear nerve (VIII) Cochlear branch Vestibular branch Tympanic duct Vestibular duct Cochlear duct Apical turn Spiral ganglion Modiolus Vestibular membrane Tectorial membrane Basilar membrane Middle turn Vestibular duct (scala vestibuli—contains perilymph) Organ of Corti Cochlear duct (scala media—contains endolymph) Tympanic duct (scala tympani—contains perilymph) Basal turn Temporal bone (petrous part) Cochlear nerve Vestibulocochlear nerve (VIII) From oval window To round window Vestibular duct (from oval window) Vestibular membrane Organ of Corti Basal turn Basilar membrane Tympanic duct (to round window) Sectional view of cochlear spiral LM 60 Apical turn Middle turn Vestibular duct (scala vestibuli) Cochlear duct (scala media) Tympanic duct (scala tympani) Cochlear branch Spiral ganglion
- 69. © 2012 Pearson Education, Inc. Figure 18.17d–f The Cochlea and Organ of Corti A color-enhanced SEM showing a portion of the receptor surface of the organ of Corti Diagrammatic and histological sections through the receptor hair cell complex of the organ of Corti Three-dimensional section showing the detail of the cochlear chambers, tectorial membrane, and organ of Corti Bony cochlear wall Vestibular duct Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Tympanic duct Organ of Corti Spiral ganglion Cochlear branch of N VIII Cochlear duct (scala media) Vestibular membrane Tectorial membrane Organ of Corti LM 125 Tympanic duct (scala tympani) Basilar membrane Hair cells of organ of Corti Spiral ganglion cells of cochlear nerve Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers Stereocilia of inner hair cells Stereocilia of outer hair cells Surface of the organ of Corti SEM 1320
- 70. © 2012 Pearson Education, Inc. Equilibrium and Hearing • Auditory Pathways (continued) • As the perilymph moves: • Pressure is put on the scala media • This pressure distorts the hair cells of the organ of Corti • This distortion depolarizes the neurons • Nerve signals are sent to the brain via CN VIII ANIMATION The Ear: Receptor Complexes
- 71. © 2012 Pearson Education, Inc. Figure 18.17de The Cochlea and Organ of Corti Diagrammatic and histological sections through the receptor hair cell complex of the organ of Corti Three-dimensional section showing the detail of the cochlear chambers, tectorial membrane, and organ of Corti Bony cochlear wall Vestibular duct Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Tympanic duct Organ of Corti Spiral ganglion Cochlear branch of N VIII Cochlear duct (scala media) Vestibular membrane Tectorial membrane Organ of Corti LM 125 Tympanic duct (scala tympani) Basilar membrane Hair cells of organ of Corti Spiral ganglion cells of cochlear nerve Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers
- 72. © 2012 Pearson Education, Inc. Figure 18.18 Pathways for Auditory Sensations KEY First-order neuron Second-order neuron Third-order neuron Fourth-order neuron High-frequency sounds Low-frequency sounds Cochlea Cochlear branch Vestibulocochlear nerve (N VIII) Cochlear nuclei Vestibular branch To ipsilateral auditory cortex Superior olivary nucleus Motor output to spinal cord through the tectospinal tracts Motor output to cranial nerve nuclei Inferior colliculus (mesencephalon) Medial geniculate nucleus (thalamus) Low-frequency sounds Auditory cortex (temporal lobe) High- frequency sounds Thalamus
- 73. © 2012 Pearson Education, Inc. Vision • Vision • Accessory structures of the eye • Palpebrae (eyelids) • Medial and lateral canthus (connect the eyelids at the corners of the eye) • Palpebral fissure (area between the eyelids) • Eyelashes (contain root hair plexus, which triggers the blinking reflex) • Conjunctiva (epithelial lining of the eyelids) • Glands: glands of Zeis, tarsal glands, lacrimal gland, lacrimal caruncle
- 74. © 2012 Pearson Education, Inc. Figure 18.19a Accessory Structures of the Eye, Part I Superficial anatomy of the right eye and its accessory structures Pupil Corneal limbus Lateral canthus Sclera Eyelashes Palpebra Palpebral fissure Medial canthus Lacrimal caruncle
- 75. © 2012 Pearson Education, Inc. Figure 18.19c Accessory Structures of the Eye, Part I Diagrammatic representation of a deeper dissection of the right eye showing its position within the orbit and its relationship to accessory structures, especially the lacrimal apparatus Opening of nasolacrimal duct Inferior nasal concha Nasolacrimal duct Lacrimal sac Inferior lacrimal canaliculus Medial canthus Superior lacrimal canaliculus Lacrimal punctum Tendon of superior oblique muscle Inferior oblique muscle Inferior rectus muscle Superior rectus muscle Lacrimal gland ducts Lower eyelid Lateral canthus Lacrimal gland
- 76. © 2012 Pearson Education, Inc. Vision • Accessory Structures of the Eye • Conjunctiva • Covers the inside lining of the eyelids and the outside lining of the eye • Fluid production helps prevent these layers from becoming dry • Palpebral conjunctiva • Inner lining of the eyelids • Ocular conjunctiva • Outer lining of the eye
- 77. © 2012 Pearson Education, Inc. Vision • Accessory Structures • Glands • All of the glands are for protection or lubrication • Glands of Zeis: sebaceous glands / associated with eyelashes • Tarsal glands: secrete a lipid-rich product / keeps the eyelids from sticking together / located along the inner margin of the eyelids • Lacrimal glands: produce tears / located at the superior, lateral portion of the eye • Lacrimal caruncle glands: produce thick secretions / located within the canthus areas
- 78. © 2012 Pearson Education, Inc. Vision • Accessory Structures • Glands • An infection of the tarsal gland may result in a cyst • An infection of any of the other glands may result in a sty
- 79. © 2012 Pearson Education, Inc. Vision • Accessory Structures • Lacrimal glands • Part of the lacrimal apparatus • The lacrimal apparatus consists of: • Lacrimal glands (produce tears) • Lacrimal canaliculi • Lacrimal sac • Nasolacrimal duct
- 80. © 2012 Pearson Education, Inc. Vision • Accessory Structures • Lacrimal glands (continued) • Tears are produced by the lacrimal glands • Flow over the ocular surface • Flow into the nasolacrimal canal (foramen) • This foramen enters into the nasal cavity • Therefore, when you sob heavily, tears flow across your eye and down your face and also through the nasolacrimal canal into your nose and out, resulting in a “runny” nose ANIMATION The Eye: Accessory Structures
- 81. © 2012 Pearson Education, Inc. Vision • The Eyes • Consist of: • Sclera • Cornea • Pupil • Iris • Lens • Anterior cavity • Posterior cavity • Three tunics: • (1) fibrous tunic, (2) vascular tunic, and (3) neural tunic • Retina
- 82. © 2012 Pearson Education, Inc. Figure 18.21b Sectional Anatomy of the Eye Major anatomical landmarks and features in a diagrammatic view of the left eye Central retinal artery and vein Optic nerve Optic disc Fovea Retina Choroid Sclera Posterior cavity (Vitreous chamber filled with the vitreous body) Ora serrata Fornix Palpebral conjunctiva Ocular conjunctiva Ciliary body Anterior chamber (filled with aqueous humor) Lens Pupil Cornea Iris Posterior chamber (filled with aqueous humor) Corneal limbus Suspensory ligaments
- 83. © 2012 Pearson Education, Inc. Vision • The Eyes • The Fibrous Tunic (outer layer) • Makes up the sclera and cornea • Provides some degree of protection • Provides attachment sites for extra-ocular muscles • The cornea is modified sclera
- 84. © 2012 Pearson Education, Inc. Vision • The Eyes • The Vascular Tunic (middle layer) • Consists of blood vessels, lymphatics, and intrinsic eye muscles • Regulates the amount of light entering the eye • Secretes and reabsorbs aqueous fluid (aqueous humor) • Controls the shape of the lens • Includes the iris, ciliary body, and the choroid ANIMATION The Eye: Uvea Parts
- 85. © 2012 Pearson Education, Inc. Vision • The Vascular Tunic • The iris • Consists of blood vessels, pigment, and smooth muscles • The pigment creates the color of the eye • The smooth muscles contract to change the diameter of the pupil
- 86. © 2012 Pearson Education, Inc. Vision • The Vascular Tunic • The ciliary body • The ciliary bodies consist of ciliary muscles connected to suspensory ligaments, which are connected to the lens • The choroid • Highly vascularized • The innermost portion of the choroid attaches to the outermost portion of the retina ANIMATION The Eye: Ciliary Muscles
- 87. © 2012 Pearson Education, Inc. Vision • The Eyes • The Neural Tunic (inner layer) • Also called the retina • Made of two layers: (pigmented layer – outer layer) / (neural layer – inner layer) • Retina cells: rods (night vision) and cones (color vision)
- 88. © 2012 Pearson Education, Inc. Figure 18.22a The Lens and Chambers of the Eye The lens is suspended between the posterior cavity and the posterior chamber of the anterior cavity. Pigmented part Neural partNeural tunic (retina) Posterior cavity Choroid Ciliary body Iris Vascular tunic (uvea) Anterior cavity Cornea Sclera Fibrous tunic
- 89. © 2012 Pearson Education, Inc. Figure 18.21ab Sectional Anatomy of the Eye The three layers, or tunics, of the eye Fibrous tunic (sclera) Vascular tunic (choroid) Neural tunic (retina) Major anatomical landmarks and features in a diagrammatic view of the left eye Central retinal artery and vein Optic nerve Optic disc Fovea Retina Choroid Sclera Posterior cavity (Vitreous chamber filled with the vitreous body) Ora serrata Fornix Palpebral conjunctiva Ocular conjunctiva Ciliary body Anterior chamber (filled with aqueous humor) Lens Pupil Cornea Iris Posterior chamber (filled with aqueous humor) Corneal limbus Suspensory ligaments
- 90. © 2012 Pearson Education, Inc. Figure 18.23a Retinal Organization Histological organization of the retina. Note that the photoreceptors are located closest to the choroid rather than near the vitreous chamber. LIGHT Amacrine cell Horizontal cell Cone Rod Choroid Pigmented part of retina Rods and cones Bipolar cells Ganglion cells Nuclei of ganglion cells Nuclei of rods and cones Nuclei of bipolar cells The retina LM 70
- 91. © 2012 Pearson Education, Inc. Vision • Cavities and Chambers of the Eye • Anterior cavity • Anterior chamber • Posterior chamber • Filled with fluid called aqueous fluid • Posterior cavity • Vitreous chamber • Filled with fluid called vitreous fluid ANIMATION The Eye: Posterior Cavity
- 92. © 2012 Pearson Education, Inc. Vision • Cavities and Chambers of the Eye • Aqueous fluid • Sometimes called aqueous humor • Secreted by cells at the ciliary body area • Enters the posterior chamber (posterior of the iris) • Flows through the pupil area • Enters the anterior chamber • Flows through the canal of Schlemm • Enters into venous circulation
- 93. © 2012 Pearson Education, Inc. Figure 18.24 Pigmented epithelium Suspensory ligaments Posterior cavity (vitreous chamber) Lens Ciliary process Choroid Retina Sclera Conjunctiva Ciliary body Body of iris Canal of Schlemm Posterior chamber Anterior chamber Anterior cavity Cornea Pupil
- 94. © 2012 Pearson Education, Inc. Vision • Cavities and Chambers of the Eye • Vitreous fluid • Gelatinous material in the posterior chamber • Sometimes called vitreous humor • Supports the shape of the eye • Supports the position of the lens • Supports the position of the retina • Aqueous humor can flow across the vitreous fluid and over the retina
- 95. © 2012 Pearson Education, Inc. Figure 18.21d Sectional Anatomy of the Eye Sagittal section through the eye Ora serrata Conjunctiva Cornea Lens Anterior chamber Iris Posterior chamber Suspensory ligaments Ciliary body Posterior cavity (vitreous chamber) Dura mater Retina Choroid Sclera Optic nerve (N II)
- 96. © 2012 Pearson Education, Inc. Vision • Aqueous fluid • If this fluid cannot drain through the canal of Schlemm, pressure builds up • This is glaucoma • Vitreous fluid • If this fluid is not of the right consistency, the pressure is reduced against the retina • The retina may detach from the posterior wall (detached retina)
- 97. © 2012 Pearson Education, Inc. Vision • Visual Pathways • Light waves pass through the cornea • Pass through the anterior chamber • Pass through the pupil • Pass through the posterior chamber • Pass through the lens • The lens focuses the image on some part of the retina • This creates a depolarization of the neural cells • Signal is transmitted to the brain via CN II ANIMATION The Eye: Interior Parts of the Eye
- 98. © 2012 Pearson Education, Inc. Figure 18.21e Sectional Anatomy of the Eye Sagittal section through the eye Orbital fat Central artery and vein Medial rectus muscle Ethmoidal labyrinth Optic nerve Optic disc Fovea Ora serrata Ciliary body LensCiliary processes Medial canthus Lacrimal caruncle Lacrimal punctum Nose Anterior cavity Posterior chamber Anterior chamber Edge of pupil Visual axis Cornea Iris Suspensory ligament of lens Corneal limbus Conjunctiva Lower eyelid Lateral canthus Sclera Choroid Retina Posterior cavity Lateral rectus muscle
- 99. © 2012 Pearson Education, Inc. Figure 18.26 Anatomy of the Visual Pathways, Part II LEFT SIDE RIGHT SIDE Left eye only Right eye only Binocular vision Optic nerve (N II) Optic chiasm Optic tract Other hypothalamic nuclei, pineal gland, and reticular formation Suprachiasmatic nucleus Superior colliculus Lateral geniculate nucleus Projection fibers (optic radiation) Lateral geniculate nucleus RIGHT CEREBRAL HEMISPHERE LEFT CEREBRAL HEMISPHERE Visual cortex of cerebral hemispheres
- 100. © 2012 Pearson Education, Inc. Vision • Visual Pathways • The retina • There are rods and cones all over the retina • 100% cones in the fovea centralis area • The best color vision is when an object is focused on the fovea centralis • 0% rods or cones in the optic disc area • If an object is focused on this area, vision does not occur • Also known as the “blind spot” ANIMATION The Eye: Blind Spot
- 101. © 2012 Pearson Education, Inc. Vision • Visual Pathways • The retina (cont.) • The cones require light to be stimulated (that’s why we see color) • At night (still has to be at least a small amount of light), the cones deactivate and the rods begin to be activated (that’s why we can see at night but we can’t determine color at night) ANIMATION The Eye: The Retina ANIMATION The Eye: Light Path ANIMATION The Eye: Lens and Retina