Function of the Sensory Organs Huang Qin Chapter 10

Function of the

Sensory Organs

Huang Qinannyhq2000@yahoo.com.cn

Chapter 10

information(internal and external world)

awareness

sensory system:process afferent sensory information

Different energy forms of information: Pressure Temperature Light Odorant Sound wave Chemical

Skin Muscle viscera

Visual Auditory Vestibular Chemical

special sensory system

Section A Sensory Functions of Nervous System

Section B Special Sensory System Vision Hearing

Sensory Physiology

Some General Principles

Sensory System:

Section A Sensory Functions of Nervous System

sensory receptor ： structure that receive stimulus from the external or internal environment

neural pathway (conduct information : receptors brain or spinal cord)

some part of the brain (deal primarily with processing the information)

General Principles

sensory information awareness: no awareness:

hothotblood pressure fluctuateblood pressure fluctuate

sound waves sound waves

receptor potentials

action potentials electrical impulse CNS hearing sound waves

Hearing Sensory system Telephone equipment

Receiver (physics)(physiology)

code

Sensory Processing steps:

General classes of receptors (by the sensitive type of energy) Mechanoreceptor Thermoreceptor eletromagnetic receptor Chemoreceptor Nociceptor ( 伤害性 ~)

Sensory receptors

Each of the sensory receptors responds much more readily to one form of energy than to others.

Adequate stimulus : the type of energy to which a particular receptor

responds sensitively in normal function. light energylight energy sound sound energy light receptor lightenergy light receptor light a poke in eyea poke in eye

1.Adequate stimulus of receptors

Sensory receptor （ energy forms ---electrical language ） 1.separate cell 2.specialized ending of afferent neuron

感受器电位发生器电位

Receptor potentialgenerator potential

2.Transduction of receptors

Receptor/generator potential

不具有“全或无”性质有总和现象呈电紧张形式短距离扩布

action potential

（ energy forms ---electrical language ） 基本信息：刺激的模式、强度、部位、时间 刺激的强度 感受器 单一神经纤维上冲动频率 传输的神经纤维数目

3.Coding action of receptors

Adaptation

4. Adaptation of receptors

Rapidly adapting receptors: clothes pressing on one’s skinclothes pressing on one’s skin Slowly adapting receptors: joint and muscle receptorsjoint and muscle receptors ： ： standing for long timestanding for long time

Visual Function of EyeAdequate stimulus: electromagnetic wave of 370-740 nm

外层：角膜、巩膜 中层：脉络膜、睫状体、虹膜 内层：视网膜

Optical system ：Cornea Aqueous humorCrystalline lensVitreous humor (body)

Optics characteristics of dioptric system of eye

scatter

concave lens

focus

convex lens

Reduced eye

ab/AB=bn/Bn ab=AB*bn/Bn

Simplifiedschematically

The parallel rays focus on the retina (6 m away)

The scattering rays focus behind the retina (within 6 m)

1. lens change to convex ：near object→blurred image→Via the optic nerve to the visual cortex→midbrain →Parasympathetic fibers→contraction of the ciliary muscle→loose of the zonular fibers→increases curvature of the lens→the image moves forward to the retina → clear vision

Accommodation of eye

meters

6 meters

Near point ： means the minimum distance that the eye can see the object clearly.

depends on ：flexibility of the lens

AgeThe flexibility decreases, the accommodation decreases too, the near point moves away from cornea. (presbyopia)

2.pupillary constriction ：function: control the light --- eye reduces spherical and chromatic aberrations

Parasympathetic fiber in the oculomotornerve→Contraction of the sphincter of iris

3.convergence of the eyeball (eye axle)

Function: ensures the rays from the object to fall on the corresponding part of each retina (diplopia, double vision)

Oculomotor nerve→Contraction of the two medial rectus muscles

Pupillary light reflex

Means that the size of pupil changes with the intensity of rays.

Rays → retina → tectum of midbrain→ E-W’s nucleus → Parasympathetic fiber in

the oculomotor nerve → Contraction of the sphincter of pupil （ both side ）

Significance ： regulates the ray amount entering eye ， protects the retina

diagnose

1.5 ~ 8.0 mm

concave lensmyopia

hyperopia

Astigmatism

convex lens

normal

cylindrical lens

abnormal accommodation

near object

far object

眼的折光能力和调节能力异常 1. 近视： 原因：眼球前后径过长或眼折光过度，使远处 物体发来的平行光线聚焦于视网膜之前 而致物象模糊，近点移近。 矫正 : 凹透镜

2. 远视： 原因：眼球前后径过短，少数因眼折光能力不 足，使远处物体发来的平行光线聚焦于 视网膜之后而致视物模糊，近点移远。 矫正 : 凸透镜

3. 散光： 原因：折光表面不呈正球面，如角膜，远物发 来的平行光线有的聚焦于视网膜的前方， 有的聚焦于视网膜的后方，引起视物模糊 或变形。 矫正：适当的柱面镜

Structure of retina and two photosensory transduction system

Retinal layers ：①pigment epithelial layer(melanin granule and vitA)protection and nutrition( to Photoreceptor cell)

Retina

Outer segment: (visual pigment) rod: thin,rod-like cone: conical

Inner segment:

Cell body:

Synaptic terminals:

② Photoreceptor cell layer 视锥视杆

rod cone

光 - 电转换的关键部位：外段静息电位：约为 -30mV ～ -40mV

机制：无光照时视杆细胞的外段膜对 Na+ 有 较大的通透性，使 Na+ 有一定程度的 内流所致

视杆细胞外段的超微结构和感受器电位

感受器电位：超极化型慢电位机制：光量子被视紫红质吸收→视蛋白变构→传递蛋白激活→磷酸二脂酶激活→

cGMP 大量分解→外段膜 Na+ 通道开放减少-→ 超级化型感受器电位 - 电紧张形式→视终足，影响终足处的递质释放。

Na+

--- -

③bipolar cell layer （双极细胞）Connect to synaptic terminals

and ganglion cell

④ ganglion cell layer ( 神经节细胞 )

Two photosensory transduction system items cone system rod system distribution center(more) peripheral(more) transmit : convergence low high visual pigment iodopsin(3) rhodopsin light sensitivity bad better vision photopic scotopic visual acuity good bad Resolving power good bad color vision yes no animal species chicken Owl

Mechanism of photosensory transduction in Rods

No VitA: nyctalopia(night blindness)

scotopsin

rhodopsin

11-cis-retinene

VitA

11-trans-retinene

dark light rhodopsin

Mechanism of photosensory transduction in Rods

No VitA: nyctalopia(night blindness)

3 proteins

rhodopsin

11-cis-retinene

VitA

11-trans-retinene

dark light iodopsin

bright

dark

compose

rhodopsin in rods

decompose

视网膜的视觉信息处理（ Information disposal of retina ）光照→感光细胞产生感受器电位→电紧张性扩布 →突触前膜释放递质→双极细胞发生慢电位变化→神经节细胞产生动作电位→视神经→视觉中枢→产生视觉。

Dark adaptationthe process that when a person goes into a dark room ， he can see something after sometime.

Rhodopsin synthesis increases

Light adaptation

the process that when a person goes into a light place ， he can see something clearly after a few seconds.

(Rhodopsin decomposes, cone system is working)

Tricolor theory of color vision iodopsin: red-sensitive cones green-sensitive cones blue-sensitive cones

combination of blue, green and red cones

trichromat dichromat

monochromat( 全色盲 )

Visual acuity ：means the maximal ability that eyes distinguish

the minimum distance of two points.Photo receptor cell

Visual field the entire field of vision

of an individual eye which only looks on one point.

nasal halves

temporal

- Define sensory receptor and sensory transduction.-How is imformation about stimulus intensity coded by the nervous system?- Describe accomriodation of eyes.-Compare the characteristics of rods and cones.-Describe the mechanism of photoreceptor cell potential generation.-List the sequence of events that occurs between the entry of a sound wave into the external auditory canal and the firing of action potentials in the cochlear nerve.- Describe vestibular apparatus and edequaate stimulus.-What is the relationship betweet head movement and cupula movement in a semicircular canal?

C10 SENSE ORGANS