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Chapter 3 The Special Senses 特殊感覺 郭進榮 Jinn-Rung, Kuo 張菁萍Ching-Ping Chang Department of Biotechnology Southern Taiwan University 一般感覺 感覺 特殊感覺 中樞 本體感覺 腦, 脊髓 周邊 運動 視覺傳遞路徑 17 眼睛 (eyeball) 眼球運動肌肉 視神經 1/6 視神經 Figure 15.7a, b 水晶體 後腔玻璃狀液 前腔水樣液 1.纖維層: 角膜 (Cornea), 鞏膜(Sclera) 2.血管層: -脈絡膜 (Chloroid), -睫狀體 (睫狀肌,睫狀突起) -虹膜 (環狀肌,放射狀肌) 3.神經層 (視網膜)(Retina),感覺層 -視桿 (Rod).弱光視覺,夜視,區別明暗影子 -視錐 (Cone).強光視覺,彩色視覺 前房(角膜-虹膜) 後房(虹膜-水晶體) Anterior Segment 前房(角膜-虹膜) 後房(虹膜-水晶體 Figure 15.12 Structure of the Eyeball Figure 15.8a Structure of the Eyeball • A slightly irregular hollow sphere with anterior and posterior poles • The wall is composed of three tunics – fibrous, vascular, and sensory • The internal cavity is filled with fluids called humors • The lens separates the internal cavity into anterior and posterior segments Fibrous Tunic (纖維層) • Forms the outermost coat of the eye and is composed of: – Opaque sclera (posteriorly)鞏膜 – Clear cornea (anteriorly) 角膜 • The sclera protects the eye and anchors extrinsic muscles • The cornea lets light enter the eye Vascular Tunic (Uvea):血管層 Choroid Region • Has three regions: - Choroid 脈絡膜 - Ciliary body 睫狀體 - Iris 虹膜 • Choroid region – A dark brown membrane that forms the posterior portion of the uvea – Supplies blood to all eye tunics Vascular Tunic: Ciliary Body睫狀體 • A thickened ring of tissue surrounding the lens • Composed of smooth muscle bundles (ciliary muscles) • Anchors the suspensory ligament懸韌帶 that holds the lens in place Vascular Tunic: Iris 虹膜 • The colored part of the eye • Pupil – central opening of the iris (瞳孔) – Regulates the amount of light entering the eye during: • Close vision and bright light – pupils constrict • Distant vision and dim light – pupils dilate • Changes in emotional state – pupils dilate when the subject matter is appealing or requires problem-solving skills 副交感 交感 Sensory Tunic: Retina視網膜 • A delicate two-layered membrane • Pigmented layer – the outer layer that absorbs light and prevents its scattering(色素層) • Neural layer, which contains(神經層) – Photoreceptors that transduce light energy – Bipolar cells and ganglion cells – Amacrine and horizontal cells The Retina: Photoreceptors • Rods: 桿細胞 – Respond to dim light (夜視) – Are used for peripheral vision • Cones:錐細胞(明視,彩色視覺) – Respond to bright light – Have high-acuity color vision – Are found in the macula lutea – Are concentrated in the fovea centralis Blood Supply to the Retina • The neural retina receives its blood supply from two sources – The outer third receives its blood from the choroid – The inner two-thirds is served by the central artery and vein • Small vessels radiate out from the optic disc and can be seen with an ophthalmoscope Lens水晶體 (透明) • A biconvex, transparent, flexible, avascular structure that: – Allows precise focusing of light onto the retina – Is composed of epithelium and lens fibers • Lens epithelium – anterior cells that differentiate into lens fibers • Lens fibers – cells filled with the transparent protein crystallin • With age, the lens becomes more compact and dense and loses its elasticity (白內障) Light 電磁波 可見光 400-700奈米 視網脈上不同錐細胞對 不同波長有反應 Figure 15.14 Focusing Light on the Retina • Pathway of light entering the eye: cornea, aqueous humor, lens, vitreous humor, and the neural layer of the retina to the photoreceptors • Light is refracted: – At the cornea – Entering the lens – Leaving the lens • The lens curvature and shape allow for fine focusing of an image Refraction and Lenses Figure 15.16 Focusing for Distant Vision • Light from a distance needs little adjustment for proper focusing • Far point of vision – the distance beyond which the lens does not need to change shape to focus (20 ft.) Figure 15.17a Focusing for Close Vision • Close vision requires: – Accommodation – changing the lens shape by ciliary muscles to increase refractory power – Constriction – the pupillary reflex constricts the pupils to prevent divergent light rays from entering the eye – Convergence – medial rotation of the eyeballs toward the object being viewed Problems of Refraction • Emmetropic eye – normal eye with light focused properly • Myopic eye (nearsighted近視) – the focal point is in front of the retina – Corrected with a concave lens • Hyperopic eye (farsighted遠視) – the focal point is behind the retina – Corrected with a convex lens Problems of Refraction Figure 15.18 The Ear: Hearing and Balance .內耳 (迷路) -耳蝸,三個半規管 -骨性迷路. -膜性迷路 中耳. 外耳. - 錘骨(malleus) –石占骨( Incus) –鐙骨(Stapes) 鼓膜 卵圓窗=前庭窗 耳翼, 外耳道,鼓膜 - 耳咽管,圓窗 Figure 15.25a 圖9-8 2.5cm Outer Ear • The auricle (pinna) is composed of: – The helix (rim) – The lobule (earlobe) • External auditory canal – Short, curved tube filled with ceruminous glands Outer Ear • Tympanic membrane 鼓膜(eardrum) – Thin connective tissue membrane that vibrates in response to sound – Transfers sound energy to the middle ear ossicles聽小骨 – Boundary between outer and middle ears Middle Ear (Tympanic Cavity鼓室) • A small, air-filled, mucosa-lined cavity – Flanked laterally by the eardrum – Flanked medially by the oval and round windows • Epitympanic recess – superior portion of the middle ear • Pharyngotympanic tube – connects the middle ear to the nasopharynx – Equalizes pressure in the middle ear cavity with the external air pressure Middle Ear (Tympanic Cavity) 耳咽管 Figure 15.25b Fig. 9.13 聽覺器 The Cochlea Figure 15.28 Properties of Sound • Sound is: – A pressure disturbance (alternating areas of high and low pressure) originating from a vibrating object – Composed of areas of rarefaction and compression – Represented by a sine wave in wavelength, frequency, and amplitude • Frequency – the number of waves that pass a given point in a given time • Pitch – perception of different frequencies (we hear from 20–20,000 Hz) Properties of Sound • Amplitude – intensity of a sound measured in decibels (dB)分貝 • Loudness – subjective interpretation of sound intensity Figure 15.29 Transmission of Sound to the Inner Ear Figure 15.31 聽覺傳遞路徑 聲波 -> 外耳道-> 鼓膜 -> 錘骨 ->石占骨 -> 鐙骨 ->卵圓窗 ->外淋巴液 ->耳蝸管內淋巴液 -> 毛細胞去極化 ->耳蝸神經 ->延髓耳蝸核 ->中腦下丘 ->丘腦內內側膝狀體->大腦顳聽 覺區 (41, 42) Sound and Mechanisms of Hearing • Sound vibrations beat against the eardrum • The eardrum pushes against the ossicles, which presses fluid in the inner ear against the oval and round windows – This movement sets up shearing forces that pull on hair cells – Moving hair cells stimulates the cochlear nerve that sends impulses to the brain Transmission of Sound to the Inner Ear • The route of sound to the inner ear follows this pathway: – Outer ear – pinna, auditory canal, eardrum – Middle ear – malleus, incus, and stapes to the oval window – Inner ear – scalas vestibuli and tympani to the cochlear duct • Stimulation of the organ of Corti • Generation of impulses in the cochlear nerve