Physiology

XiaoLan HU (胡晓兰), MD & PhD

Associate Professor of Department of Physiology

Email: huxiaolan1998@yahoo.com.cn

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?