C9 Function of the Sensory Organs

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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?