Chapter 3 The Special Senses

郭進榮 Jinn-Rung, Kuo張菁萍 Ching-Ping Chang

Department of BiotechnologySouthern Taiwan University

特殊感覺

感覺

運動

中樞

腦 , 脊髓

周邊

一般感覺

特殊感覺

本體感覺

17視覺傳遞路徑

眼睛 (eyeball)

眼球運動肌肉

Figure 15.7a, b

視神經1/6

視神經

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

後腔玻璃狀液

前腔水樣液

水晶體

前房 ( 角膜 - 虹膜 ) 後房 ( 虹膜 - 水晶體 )

Anterior Segment

Figure 15.12

前房 ( 角膜 - 虹膜 )後房 ( 虹膜 - 水晶體

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

Figure 15.14

400-700奈米

電磁波

可見光

視網脈上不同錐細胞對不同波長有反應

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

Figure 15.25a

外耳 . 耳翼 , 外耳道 , 鼓膜

中耳 . - 錘骨 (malleus) –石占骨 ( Incus) –鐙骨(Stapes) 鼓膜 卵圓窗 = 前庭窗 - 耳咽管 , 圓窗

. 內耳 ( 迷路 ) - 耳蝸 , 三個半規管 - 骨性迷路 . - 膜性迷路

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)

Figure 15.25b

耳咽管

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