Transcript C9 Function of the Sensory Organs

Chapter 10
Function of the
Sensory Organs
Huang Qin
[email protected]
information(internal and external world)
Different energy forms
sensory system:
of information:
process afferent sensory information
Pressure
Temperature
Light
Odorant
awareness
Sound wave
Chemical
 Skin
Muscle
viscera
 Visual
Auditory
Vestibular
Chemical
special sensory system
Sensory Physiology
Section A Sensory Functions of Nervous System
Some General Principles
Section B
Special Sensory System
Vision
Hearing
Section A
Sensory Functions of Nervous System
General Principles
Sensory 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)
sensory information
awareness:
no awareness:
hot
blood pressure fluctuate
Sensory Processing steps:
Hearing Sensory system
sound waves
Telephone equipment
sound waves
receptor potentials
action potentials
code
CNS (physiology)
hearing
electrical impulse
Receiver (physics)
sound waves
Sensory receptors
 General classes of receptors
(by the sensitive type of energy)
Mechanoreceptor
Thermoreceptor
eletromagnetic receptor
Chemoreceptor
Nociceptor (伤害性~)
1.Adequate stimulus of 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 energy
sound energy
a poke in eye
light receptor
light
2.Transduction of receptors
Sensory receptor （energy forms ---electrical language）
1.separate cell
2.specialized ending of afferent neuron
发生器电位
感受器电位
generator potential
Receptor potential
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
3.Coding action of receptors
（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
4. Adaptation of receptors
Adaptation
Rapidly adapting receptors:
clothes pressing on one’s skin
Slowly adapting receptors:
joint and muscle receptors：
standing for long time
Visual Function of Eye
Adequate 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
Optics characteristics of dioptric system of eye
Optical system：
Cornea
Aqueous humor
Crystalline lens
Vitreous humor
(body)
scatter
concave lens
focus
convex lens
Reduced eye
ab/AB=bn/Bn
Simplified
schematically
ab=AB*bn/Bn
The parallel rays focus on the retina
(6 m away)
The scattering rays focus behind the retina
(within 6 m)
Accommodation of eye
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
meters
6 meters
Near point：means the minimum distance that the
eye can see the object clearly.
depends on ：
flexibility of the lens
Age
The 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 oculomotor
nerve→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.
1.5 ~ 8.0 mm
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
normal
far object
myopia
abnormal
accommodation
concave lens
near object
hyperopia
Astigmatism
convex lens
cylindrical lens
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
Retina
Structure of retina and two photosensory
transduction system
Retinal layers：
①pigment epithelial
layer
(melanin granule and vitA)
protection and nutrition
( to Photoreceptor cell)
② Photoreceptor cell layer
视杆
Outer segment: (visual pigment)
rod: thin,rod-like
cone: conical
Inner segment:
Cell body:
Synaptic terminals:
视锥
rod
cone
视杆细胞外段的超微结构和感受器电位
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
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
Na+
-→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。
---
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
 distribution
center(more)
 transmit :
convergence
low
 visual pigment
iodopsin(3)
 light sensitivity
bad
 vision
photopic
 visual acuity
good
 Resolving power
good
 color vision
yes
 animal species
chicken
rod system
peripheral(more)
high
rhodopsin
better
scotopic
bad
bad
no
Owl
Mechanism of photosensory transduction in Rods
dark
rhodopsin
rhodopsin
light
scotopsin
11-cisretinene
VitA
11-transretinene
No VitA: nyctalopia(night blindness)
Mechanism of photosensory transduction in Rods
dark
rhodopsin
iodopsin
light
3 proteins
11-cisretinene
VitA
11-transretinene
No VitA: nyctalopia(night blindness)
rhodopsin in rods
dark
bright
compose
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 adaptation
the 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.
temporal
nasal halves
C10 SENSE ORGANS
- 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?