Physiology XiaoLan HU (胡晓兰), MD & PhD Associate Professor of Department of Physiology Email: [email protected]
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Physiology
XiaoLan HU (胡晓兰), MD & PhD
Associate Professor of Department of Physiology
Email: [email protected]
Section 1: Physiology of the Receptor and
Sensory Organs
Section 2: Somatic Sensation
Section 3: Visual Function of the Eye
Section 4: Function of the Auditory System
Section 5: Vestibular function
Functions of the Sensory Organs
To master the physiological characteristics of sensory receptors
To master dioptric system of eye and its regulation
To master photosensory and transduction system of eye
To master the pathways of sound wave into the inner ear
To master the functions of inner ear
To understand some conceptions (see vocabulary)
To understand the function of vestibular organ
To learn the characteristics of the smell and taste receptors
Objectives
What is Receptor?
Pacinian corpuscles Meissner's Corpuscles Muscle spindle
1.By Location Exteroceptor
Visceral receptor
Proprioceptor
Classification of Receptors
2. By Stimulus Type
Mechanoreceptor
Thermoreceptor
Nociceptor
Photoreceptor
Chemoreceptor
3. By Complexity
Simple receptor
Complex receptor
What is adequate stimulus of the receptor?
What is sensory threshold Intensity threshold
Temporal threshold
Area threshold
Discrimination threshold
What is transducer function of the receptor?
Receptor potential and generator potential
Features of receptor potential: like local potential
Not “all or nothing”
Electrotonic propagation
Temporal & spatial summation
What is coding function of the receptor?
What is adaptation of the receptor?
Classification:
rapidly adapting receptor
slowly adapting receptor
What is somatic sensation? Classification: Superficial somatic sensation
Deep somatic sensation:
What is proprioceptor?
What is proprioception?
Muscle spindle Tendon organ
What is touch and pressure senses?
What is temperature senses?
What is pain sense? Characteristics of nociceptor:
No adequate stimulus.
Slowly adapting receptor.
Classification of nociceptor:
Mechanical nociceptor:
Mechanical temperature nociceptor
Polymodal nociceptor:
Algogenic substance:
Exogenous algogenic substance
Endogenous algogenic substance
The basic process of pain
Section 3: Visual Function of the Eye
Optic characteristics of dioptric system
Dioptric System
Four refractive interface
light must pass though four
medium with different
refractive power, and have to
pass though four refractive
interface with different diopter
What is reduced eye ?
ab
AB
bn
Bn =
Using reduced eye, we can calculate the image size on the retina.
What is accommodation of crystalline lens?
See the far object: ciliary muscles
relaxation, suspensory ligament
tension, lens become flat
See the near object: ciliary muscles
contraction, suspensory ligament
relaxation, the lens become convex
forward and backward
What is accommodation of pupil?
Types:
Pupillary accommodation reflex,
Pupillary light reflex,
Consensual pupillary light reflex
What is convergence reflex?
What is emmetropia?
What is ametropia?
Myopia
Hyperopia
Astigmatism.
Structure of Retina
From outside to inside:
Pigment layer
Photoreceptor cell layer
Bipolar cell layer
Ganglion cell layer
The structure of rod and cone cells
Connection of two photosensitive cells with bipolar cells
Rods Cones
Quantity Many(1.2x108) Few(6x106)
Outer segment Like rod Like cone
Distribution More numerous in periphery Concentrated in fovea
Connection Much convergence in retina Little convergence in retina
Visual pigment Rhodopsin Three cone pigments
Function Night vision Day vision
Low acuity
Vision in shades of gray
High sensitivity
High acuity
Color vision
Low sensitivity
What is physiological blind spot?
Distribution of cones and rods in the retina
Cones
Rods
Nasal retina Temporal retina
Distance from the fovea nu
mb
er o
f th
e ro
ds
an
d
con
es
Blind
Blind spot test
Place your eye a distance from the screen about 20 ~
30cm, then close the left eye，and staring at the circular
with the right eye, the cross will disappear at a certain
position.
Cones system Rods system
Distribution Fovea and macular 6mm far away from the fovea
Synaptic
connections cone-bipolar-ganglion rod-bipolar-ganglion
Characteristic of
connections Single Convergent
Characteristics
of function
Low sensitivity High sensitivity
Bright light Dim light
High acuity Low acuity
Photopic vision ,color Scotopic vision, no color
Photopigment Porphyropsin , iodopsin and
cyanopsin Rhodopsin
Mechanism of Photoreception of the Rod
1. Photochemical Reaction of Rhodopsin
.
Rhodopsin opsin + retinal
light
Mechanism of Photoreception of the Rod
2. Receptor Potential of Rods.
Trichromatic theory of color vision
Red, green, blue are called trichromacy
What is color blindness ?
Total color blindness Types:
Partial color blindness
Sex-linked condition:
Genes on X chromosome, so more common in men.
red blindness
green blindness
Non-sex-linked condition
Blue blindness
Total color blindness
What is color feebleness ?
What is visual acuity?
What is visua1 angle?
How to judge visual acuity?
What is dark adaptation?
What is light adaptation?
What is visual field?
Size of visual field: white > yellow and blue > red > green
Temporal visual field > Nasal visual field
What are afterimage and fusion phenomenon?
What are binocular vision and stereoscopic vision?
What is hearing?
What is auditory threshold?
What is maximum auditory threshold?
What is auditory sensation area?
The structure of ear External ear：auricle and external auditory meatus
Middle ear：tympanic membrane， ossicular chain
（malleus, incus stapes），chorda tympani, auditory tube
Inner ear: cochlea and vestibule
Auricle:
collect sound waves
help to distinguish the direction of sound
External auditory meatus:
sound wave conduction
resonance effect
Functions of the External Ear
Feature: A translucent
membrane, shallow funnel shape,
with a certain tension, high
sensitivity, good frequency
response.
Function: can truly transmit
the vibration of sound wave to
the ossicular chain .
Tympanic membrane
ossicular chain
Feature:
connected by malleus, incus,
stapes in sequence。
Function:
Enhanced vibration pressure,
reduce the amplitude of vibration,
prevent the round window
membrane damage due to the
excessive amplitude of vibration
auditory tube
Feature:
A tube connecting tympanic membrane
and pharyngeal cavity
Function:
①Adjust the air pressure balance of
both sides in tympanic membrane ,
maintain the normal position, shape and
vibration of tympanic membrane
②cilia movement on mucosa of
auditory tube can excrete the secretion
in the middle ear.
Pathways of Sound Wave into the inner ear
air conduction: normal way
bone conduction: unnormal way
Air conduction
Sound waves
External auditory meatus
Tympanic membrane
Ossicular chain
Oval window
Vestibular duct
Air in the drum
Round window
Tympanic duct
main way
Bone conduction Sound waves
Vibration of temporal bone
Vibration of endolymph in cochlea
Function of Inner Ear
Component: composed of cochlea and
vestibular organ
Function: convert the mechanical vibration
in cochlear into nerve impulses on auditory
nerve fibers
Cochlea Fluids in the cochlea is different , the Fluids in the scala
vestibuli and scala tympani are perilymph, but the Fluid
in scala media is endolymph.
Organ of Corti Organ of Corti contain about 16,000 cochlear hair cells.
The top of each hair cell has hundreds of cilia, and the
bottom of hair cells is rich in the auditory nerve endings
Vibration of Basilar Membrane and
Traveling Wave Theory
• When sound wave vibration reach to oval
window , the pressure changes can cause the oval
window membrane to move. this will cause the
basilar membrane to vibrate. the vibration begin
from the bottom of the basilar membrane,
according to traveling wave theory, the vibration
of basilar membrane will spread to the top of the
cochlea.
When the basilar membrane move, can cause a shearing
action between the tectorial membrane and the organ of
Corti, cause hair cells to bend
Hair cell excitation
Bioelectric phenomenon of the cochlea
What is endocochlear potential or endolymphatic
potential?
What is cochlear microphonic potential (CM)?
What is action potential of auditory nerve?
Section 5: Vestibular function
Receptor cell of Vestibular
scanning electron microscope of hair cells
Adequate stimulus of vestibular
The crista ampullaris of semicircular canal can sense
angular acceleration and deceleration
The macula of utricle can sense linear acceleration in
horizontal direction
The macula of saccule can sense linear acceleration in
perpendicular direction
Vestibular response
What is vestibular postural reflex?
What is vestibular autonomic reaction?
What is nystagmus?
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