1 Sensory Physiology Sensory Physiology Dr. ZHANG Xiong Dept. of Physiology ZJU School of Medicine Http:// /10.202.77.12 What is a sense? Part 1. Summary of sense What is a sense? A sense of warmth, hunger, pain, light, etc. A part of reflex arc which carry on the basal function of nervous system How to produce a sense? Invoked by a kind of stimulation and produced by brain
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1
Sensory PhysiologySensory Physiology
Dr. ZHANG Xiong
Dept. of Physiology
ZJU School of Medicine
Http:// /10.202.77.12
What is a sense?
Part 1. Summary of sense
What is a sense?A sense of warmth, hunger, pain, light, etc.
A part of reflex arc which carry on the basal function of
nervous system
How to produce a sense?Invoked by a kind of stimulation and produced by brain
2
Definition of ReceptorsSpecialized cells or group of nerve
Receptors and Sense Organs
Specialized cells or group of nerve endings that respond to stimuli
TypesMechanoreceptorChemoreceptorEl t ti tElectromagnetic receptorThermoreceptorNociceptor
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Definition of Sense OrgansA i li d t t h t llA specialized organ or structure where receptor cells are concentrated and supported by affiliated cells
TypesEye--VisionEar--HearingInner Ear--EquilibriumNose--SmellTongue--Taste
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Physiological Properties of Receptors
Ad t ti lAdequate stimulusParticular form of energy to which a receptor is most sensitive- Mechanoreceptor- Chemoreceptor
Electromagneticreceptor (photoreceptor)- Electromagneticreceptor (photoreceptor)- Thermoreceptor- Voltage receptor- etc.
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Sensory transductionSensory transduction
Receptor potential
An intermediate step between stimulus
and nerve impulse
Graded according to stimulus intensity
Generator potential
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Stimulus features are electrically
encoded
Frequency code
Population code
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AdaptationWhen a maintained stimulus of constant strength is applied to a receptor, the frequency of the action potentials in its sensory nerve declines over a period of time
Rapidly adapting receptorRapidly adapting receptor
Slowly adapting receptor
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Part 2. Visual Sense
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Visual Sense Organ- Eye
Eye -photoreceptor
Structure of the Eye
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Function of the Eye
Refracti e s stemRefractive system
Receptor system-
Retina
Refractive system
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Refraction of Light in the Eye
Function of refractive System
13
Reduced eye model
It will help to make a clear images in retina for the
Accommodation of Refractive Function
It will help to make a clear images in retina for the
objects in the different distance.
Accommodation of lens
Accommodation of PupilsAccommodation of Pupils
Convergence of Eyeballs
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Accommodation of Lens
Accommodation of Lens
Controlled by theControlled by the parasympathetic nerves
Parasympathetic nerves(+)→ciliary
l imuscle contraction →lens ligament relaxation → lens becomes thicker → refractive power↑
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Far point of visionFar point of vision
The farthest point at which an object can be
seen distinctly by the eye
Near point of vision
The nearest point at which an object can be
seen distinctly by the eye
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Accommodation of Pupils
Near reflex of the pupilNear reflex of the pupil
The pupil constricts when an individual
looks at a near object
Pupillary light reflex
Consensual light reflex
Convergence of Eyeballs
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Abnormalities of Refractive Function
Myopia
(Nearsightedness)
Hyperopia
(Farsightedness)
Astigmatism
Presbyopia
Myopia
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Hyperopia
Astigmatism
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Presbyopia
Receptor system-Retina
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Photoreceptive Function of Retina
PhotoreceptorRod
Rhodopsin
Coneh d i lik iRhodopsin-like pigments
red-sensitive pigmentgreen-sensetiveblue-sensitive
Rod cell -- Scotopic Vision SystemNot color sensitiveMore sensitive to light (more rhodopsin)g ( p )Mainly peripheral distribution
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Cone cell -- Photopic Vision System
Color sensitive (3 types of rhodopsin-like pigments)Less sensitive to lightLess sensitive to light Mainly distributed in fovea
Mechanism of photoreceptor
Photochemistry of rhodopsin
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R l f i i A i hRole of vitamin A in the
formation of rhodopsin
Nyctalopia (Night
blindness)
Generation of a
hyperpolarized
receptor potentialp p
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Color vision by the conesTrichromacy theory
Blue green or red-sensitive pigmentBlue, green or red sensitive pigment
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Color Blindness
Red-green color blindnessRed-green color blindness
Blue weakness
Inheritance of red-green color blindness
A typical pedigree of inheritance of red-green color blindness shows the pattern of transmission.
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Information Process in Retina
Depolarizing andDepolarizing and
hyperpolarizing cells
Bipolar cell
Ganglion cell
Action potential
60 rods and 2 cones
converge on 1 cell
Action potential conduction
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Some Phenomena Related with Vision
Visual acuity
The visual ability to
resolve fine detail
Some Phenomena Related with Vision
Dark adaptation
Light adaptation
MechanismsChanges in concentrations of 11-cis-retinalChange in pupillary sizeNeural adaptation
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Some Phenomena Related with Vision
Visual field
not circular
White＞yellow＞
d＞red＞green
Blind spot
Some Phenomena Related with Vision
Binocular vision and stereopsis
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Video Review
General Questions
Terms:
Receptor potential
Visual acuity
Dark adaptation
Describe the mechanism of accommodation of the eyeDescribe the mechanism of accommodation of the eye.
What are the differences between scotopic vision system
and photopic vision system?
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