独中高中生物Chapter 12 Receptors and sensation

Chapter 12
Receptors and sensation
2018
Ong Yee Sing

Objectives
• To understand the definition and types of receptors.
• To comprehend the structure of retina and visual.
• To comprehend the structure of cochlea and hearing.
• To comprehend the structure of vestibule and semi-circular canal and
balance.
• To understand the smell receptor and the production of smell.
• To understand taste receptor and the production of taste.
• To recognize the receptors of skin.

Receptors
• Specialized
nervous
structures or
more complicated
sense organs
• To receive
changes in the
surrounding and
stimuli刺激.
• Convert stimuli
into nerve
impulses
外接受器内接受器本体接受器
muscles, tendons, joints and
internal ear
the internal organs and blood vessels
skin, nose, tongue, eye and ear

Stimuli and responses
Stimulus Receptor
Afferent
neuron
Central
nervous
system
Efferent
neuron
effector
接受器
中枢
神经
系统
效应器
Create nerve impulses Feel and Analyse Carry out responses
感觉神经元运动神经元

Eyes and vision
• Eye is the
receptor which is
sensitive to light
and forms image
to generate
vision视觉.

Layers of eye ball wall
• the outermost layer is sclera巩膜
• Contains mainly collagen and some
elastic fiber
• Protection
• the middle layer is choroid脉络膜
• Vascularized and with pigment
melanin黑色素
• Provide nutrient and oxygen
• Limit uncontrolled reflection
• the inner layer is retina视网膜
• Contains light-sensitive cells
• Intercept light stimuli
Choroid
Sclera
Retina
Photoreceptor

Quiz
• Innermost layer of eyeball is
A. iris
B. retina
C. ciliary body
D. pupil

Structure of retina
• Contains two types of
photoreceptor (light
sensitive cells):
• rod cell视杆细胞
• cone cell视锥细胞
• The rod cell and cone
cell are connected to
nerve fibers.

TEM of retina
• (1) rods and cones layer. It is located below the
pigment epithelia which has been cut away
during the preparation and is not visible on this
image (black space on top). Below the rods and
cones layer you can find the
• (2) outer nuclear layer (ONL) which contains the
nuclei of the rods and cones.
• The adjacent (3) outer plexiform layer (OPL) is
followed by the (4) inner plexiform layer (IPL),
which contains numerous cell types, including
horizontal cells, bipolar cells and amacrine cells.
• At the very bottom you can see the (5) inner
nuclear layer (INL), followed by the (6) ganglion
cell layer with two (7) blood vessels shown at left
and (8) nerve fibers (which form the optical
nerve).

Distribution of rods and cones in the human
retina.
• Graph illustrates that cones are
present at a low density throughout
the retina, with a sharp peak in the
center of the fovea.
• Conversely, rods are present at high
density throughout most of the
retina, with a sharp decline in the
fovea.
• Boxes at top illustrate the appearance
of cross sections through the outer
segments of the photoreceptors at
different eccentricities.
• The increased density of cones in the
fovea is accompanied by a striking
reduction in the diameter of their
outer segments.

Spectral sensitivity of rod and cone cells

Formation of vision
• The rod and cones cells create nerve
impulses in the presence of light.
• Impulse is transmitted through nerve
fibers.
• Nerve fibers gather to form optic
nerve.
• Optic nerve sends the impulse to the
cortex of cerebrum.
• In the visual area of cortex, vision is
produced

Blind spot盲点
• Blind spot is where the optic disk
(optic nerve head) located within
the retina.
• There are no photoreceptors (i.e.,
rods or cones) in the optic disk.
• No image detection occurs in this
area.
黄点

Quiz
• The blind spot is a part of the eye's _____.
A) cornea
B) retina
C) fovea
D) lens

Rod cells
• More rod cells than cone cells.
• They spread all over the retina
but they are not found in the
fovea.
• The further away from the fovea,
the more the rod cells.
• Rod cells only produce black and
white vision (no colour).
• Sensitive to low light.
• Nocturnal animals have more rod
cells.

Visual pigment of the rod cells
• Greek rhodon ‘rose’ + opsis ‘sight’
• The rod cells contain the visual pigment感光色素
called rhodopsin视紫红质
• Rhodopsin ⇄ retinene视黄醛 + opsin视蛋白
• Rhodopsin will rapidly break down (bleach) into
retinene and opsin in the presence of light.
• During the process, energy released stimulate
light sensitive cells to produce nerve impulse.
• In the dark, retinene and opsin will recombine
into rhodopsin.
light
dark

Vision in the dark
• Rods are more sensitive to light so rod cells are the primary photoreceptor
in dim light.
• Since, rhodopsin is broken down in bright light, it takes awhile for the rod
cells to resynthesize rhodopsin and regain sensitivity.
• Dark adaptation暗适应refers to how the eye recovers its sensitivity in the
dark following exposure to bright lights.
• Since retinene is synthesized from vitamin A, a lack of vitamin A will lead
to night blindness夜盲症.
暗视
黄昏黎明视觉
明视

Cone cells
• Cone cells are less common than rod
cells.
• Cone cells are mainly concentrated at
fovea of the retina.
• Fovea is the part of the retina which gives
the highest acuity (sharpness) vision.
• The further away from fovea, the fewer is
the distribution of the cone cells.
• Cone cells are sensitive to strong light.
• Diurnal animals白天活动的动物 have more
cone cells.

Diagrammatic cross section through the
human fovea
• The overlying cellular layers and blood vessels are displaced so that
light rays are subject to a minimum of scattering before they strike
the outer segments of the cones in the center of the fovea, called
the foveola.

Quiz
• Because the fovea has a large concentration of cones, information
about ______ will be processed here.
A) dim light
B) movement
C) color
D) shape

Colour vision色觉
• Cone cells can distinguish colours.
• There are three types of cone cells each
containing a visual pigment respectively.
• The three types of visual pigment are
red, green and blue pigments.
• They have different sensitivity toward
different colour of light.
• The colour of an object that we see
depends on the quantity of stimulated
cone cells due to the overlapping action
spectra.

Quiz
• How many different types of cone code for colour in the fovea of the
retina?
A. Two
B. One
C. Three
D. None (there are no cones in the fovea - only rods)

Colour blindness
• Colour blindness is the
decreased ability to see color
or differences in color.
• The most common cause of
color blindness is an inherited
fault in the development of one
or more of the three sets of
color sensing cones in the eye,
as they are either lost, or their
action spectra greatly overlap.
reduced sensitivity to green light
(most common)
reduced sensitivity to red light reduced sensitivity to blue light
(rarest)

Red-green colour blindness
• The most common colour
blindness.
• This defect is due to the
shortage of red and green
cone cells or these cone cells
cannot distinguish green and
red colour.

X-linked recessive
• Red-green color blindness is in the
majority of cases provoked through
a defective X-chromosome.
• This concludes if a man is a carrier of
a defective X-chromosome he will
suffer from color blindness.
• On women the not defective
chromosome is in charge and
therefore she is not colorblind but a
carrier for color blindness.
• A women needs two defective X-
chromosome to be affected.

Total colour blindness
• Total colour blindness is a complete absence of
color vision.
• A person completely unable to distinguish any
color – seeing things only in grayscale (shades of
black and white).
• This phenomenon is seldom seen.
• Monochromacy is caused by the total absence of
either 2 or 3 of the cone cells, or all cone cells,
reducing vision to one dimension.

Comparison of rod and cone cells

Eyes of arthropods节肢动物
• Arthropods have
either simple eye
(ocellus)单眼 or
compound eye复
眼.

Summary
• Rod cells are sensitive to low light and only produce a black and white
image.
• Dark adaptation occurs as opsin recombines with retinene to form
rhodopsin.
• Night blindness can be resulted from a deficiency in vitamin A.
• Cone cells provide colour vision and sharp image.
• Deficiencies in the cone cells can lead to colour blindness such as
green-red colour blindness and total colour blindness.

Objectives
• To comprehend the structure of cochlea and hearing.
• To comprehend the structure of vestibule and semi-circular canal and
balance.

The ear
• The ear is both the
organ for hearing and
balance.
• Hearing – cochlea耳蜗
• Balance – semi-
circular canal and
vestibule

Quiz
• Chewing gum, yawning, and swallowing in elevators and airplanes
help to move air through the ______ tubes, which equalizes air
pressure upon ascent and descent.
A. optic
B. tympanic
C. cochlear
D. auditory (eustachian)

Structure of the ear and cochlea
外耳中耳内耳
pinna

Quiz:
Write your name, class no, class and date.

Structure of the cochlea
• Greek kokhlos “land
snail”
• Located in the inner ear.
• Three ducts filled with
lymph
• Form a labyrinth内耳迷路

The three longitudinal parallel canals
• Vestibular canal前庭管
• Uppermost - connected to the oval
window and the tympanic canal
• Contains perilymph
• Cochlea duct蜗管
• Middle
• Contains endolymph
• Contains organ of Corti
• Tympanic canal鼓管
• Lowermost - connected the round
window and the vestibular canal
• Contains perilymph

The windows
• Oval window卵圆窗 fenestra
vestibule
• Vibrations that contact the
tympanic membrane
travel through the three
ossicles and into the inner
ear through the Vestibular
canal.
• Round window圆窗
• Allow movement of the
fluid within the cochlea as
the stepes moves into the
oval window.

Quiz
• The canals contained in the spiral-shaped tubular cochlea include
_____________.
A. the vestibular, cochlear, and tympanic canals
B. the utricle and saccule
C. all branches of the organ of Corti
D. the eustachian canal and the eerie canal

organ of Corti
柯蒂氏器
organ of Corti =
• basilar membrane底膜+
• sensory hair cells感觉毛状细胞 +
• tectorial membrane盖膜
(Reissner’s membrane)
• basilar membrane
• separates the tympanic canal
from the cochlear duct
• supports a layer of sensory hair
cells

Quiz
• In the ear, the ___________ membrane forms the lower wall of
the cochlear canal.
A. semicircular
B. tectorial
C. tympanic
D. basilar

Transmission of sound
Sound
wave
Pinna外耳壳
Auditory
canal外耳道
ear drum
鼓膜 vibrates
Three cranial
bones听小骨
amplifies the
vibration
Oval window
卵圆窗
Endolymph
内淋巴液 vibrates
Tectorial
membrane盖膜
vibrates
Sensory hair cells
毛状细胞 vibrates
and generate
nerve impulses
Perilymph
外淋巴液 of the
vestibular canal
前庭管 vibrates
Vibration
transmitted to the
whole cochlea
Basilar membrane
地膜 vibrates
Auditory nerve听
神经
Cerebral cortex
大脑皮层
Hearing centre
听觉中枢
Outer ear Middle ear Inner ear

Quiz
• In the ear, when the cilia of the hair cells bend, nerve impulses
travel to the oval window.
A. True
B. False

Transmission of sound in the inner ear
No Step Type of info
1. Sound waves are transmitted into the auditory canal and causing the eardrum to vibrate. Sound wave
2. The three small cranial bones amplify the vibrations about 20 times, pass the vibrations to
the oval window which connects to inner ear.
Mechanical
vibration
3. The vibrations cause the perilymph in the vestibular canal to vibrate and transmitted rapidly
to whole cochlea
Wave
4. Vibration of perilymph causes the basilar membrane to vibrate. Wave
5. Vibration of basilar membrane causes the tectorial membrane that is flowing in the
endolymph in the to stimulate the sensory hair cells of organ Corti to flap or swing.
Wave
6. The swinging is then changed to nerve impulse which is sent to hearing center of cerebral
cortex through auditory nerve and produce hearing.
Nerve
impulse

Quiz
• Sound information is transmitted as vibrations (waves). Which of the following is
a correct order of structures used to transmit these vibrations to the Organ of
Corti? None of the lists are necessarily complete in terms of listing all structures
involved.
A. oval window to middle ear ossicles to round window to endolymph to
perilymph
B. oval window to middle ear ossicles to round window to perilymph to
endolymph
C. middle ear ossicles to tympanic membrane to endolymph to perilymph to
basilar membrane
D. tympanic membrane to middle ear ossicles to oval window to perilymph to
basilar membrane
E. tympanic membrane to middle ear ossicles to oval window to endolymph to
perilymph

How can we tell the difference in sounds?
• Sounds of different
frequencies stimulate hair
cells in different parts of
the organ of Corti,
allowing us to perceive
the subtleties of sounds
such as speech and music.
• We can also tell the origin
of the sound as sound will
not reach both ears at the
same time due to the
difference of distance
from the source to our
left and right ear.
• Some Owl species have
asymmetrically set ear
openings

Quiz
• Loud noises cause the fluid of the cochlea to vibrate ___________.
A. to a lesser degree
B. to a greater degree
C. there is no effect on degree of vibration

Quiz
• What is the punchline
(funny bit) of this
comic?
• Dogs, as many other
animals, have a
difference range of
frequency of sound
where they can hear.

Conclusion
• Hearing is initiated: Eardrum → ossicles → oval window → perilymph
→ cochlear duct → endolymph → basilar membrane → tectorial
membrane → hair cells.
• Nerve impulses generated by the hair cells are sent to hearing center
of cerebral cortex through auditory nerve.
• Sounds of different frequencies stimulate hair cells in different parts
of the organ of Corti.
• The origin of the sound is interpreted based on the time difference of
stimulation occurs in the left and right ear.

Sense of balance
• Sense of balance helps
prevent humans and animals
from falling over when
standing or moving.
• Balance is the result of a
number of body systems
working together:
• the eyes (visual system)
• ears (vestibular system =
semicircular canal半规管 +
vestibule前庭) and
• Proprioception receptors

Function of vestibule and semicircular canal
• detect the location of the
head
• maintain balance
• Vestibule
• tilting倾斜
• static equilibrium静态平衡
• Semilunar canal
• rotation旋转
• dynamic equilibrium转动平衡
• lack the auditory function

Quiz
• The sense of balance includes ___________ equilibrium.
A. horizontal and vertical
B. auditory
C. dynamic and static
D. amplitude and pitch

Quiz
• ___________ equilibrium is required when the body is moving.
A. Horizontal
B. Vertical
C. Dynamic
D. Static

Structure of the semicircular canal
• It is composed by three semi-
circular tubules which are arranged
in three planets at right angles to
each other.
• The orientations of the canals cause
a different canal to be stimulated by
movement of the head in different
planes.
• Species that are agile and have fast
locomotion have larger canals
relative to their body size than those
that move slowly.

Within the canals
• The canals are filled with endolymph.
• At the base of each canal is a swelling called ampulla壶腹.
• On the ampulla are the sensory hair cells感觉毛细胞and enclosed by
gelatinous mass胶质物.

Quiz
• The base of each of the three semicircular canals in the ear is called
the ______.
A. eustachian
B. ampulla
C. spiral organ (organ of Corti)
D. otolith

Detection of rotation
• The sensory hair
cells are
stimulated and
produce nerve
impulse.
• Nerve impulses
are sent to the
brain through
the auditory
nerve.
• When the head rotate to a certain direction, endolymph in the tube will
move to opposite direction.
• This causes the direction of gelatinous mass changed.

Response of detection
• The impulse sent to cerebellum
小脑 for the muscle to produce
corresponding reaction in order
to balance the body.
• The impulse sent to cerebrum大
脑 for regulating the direction of
movement.

Motion sickness
• When a rotation suddenly stops.
• Endolymph inside keep on moving due
to inertia.
• Nerve impulse continues to transmit.
• The ears, however, no longer detects
motion.
• The disagreement between visually
perceived movement and the vestibular
system's sense of movement cause the
dizziness feeling.

Quiz
• One form of motion sickness results because of continuous
movement of __________ in the ear.
A. fluid in the semicircular canals
B. otoliths in the utricle and saccule
C. gelatinous material in the ampullae
D. air in the eustachian tube

Structure of the vestibule前庭
• vestibular apparatus =
• utricle椭圆囊+ saccule球状囊
• The utricle, which lies
horizontally, and saccule,
which is oriented vertically.
• Both the utricle and saccule
contain endolymph, sensory
hair cells, gelatinous mass
and otoliths耳石.

hair cells long microvilli (hatched circles) on
the utricle
SEM image of the hair cells long microvilli
(hatched circles) on the utricle, revealing
long stereocilia (up to 5 µm in length)
partially surround a 9-µm kinocilium. (b)
TEM image through the elongate hair cells
and peripheral nerve bed. (c) The top of the
cell, buttressed by a long microvillus. cm,
cell membrane; cp, cuticular plate; hc, hair
cell; jc, junctional complex; lmv, long
microvilli; n, nucleus; ps, phagosomes; pnf,
peripheral nerve fibres; smv, short
microvilli.

Function of the vestibule
• The left and right utricular maculae are in the same, approximately
horizontal, plane.
• These can help to sense the situation of head by detecting linear
acceleration and the pull of gravity and maintain balance at rest.

Mechanism of detection
• The endolymph moves.
• The gravity pulls the gelatinous matrix and
the otoliths to one side.
• The hair cells are stimulated.
• Nerve impulses are sent to the brain(both
cerebellum and cerebrum) through the
auditory nerve.

Quiz
• Movement of the otoliths within the utricle and the saccule is
important for static equilibrium in the ear.
A. True
B. False

Conclusion
• The sense of balance is the result of a number of body systems
working together: the eyes, the ears (vestibular system = semicircular
canal + vestibule) and the proprioception receptors.
• The vestibule detects tilting of the head while the semilunar canal
detects rotation of the head.
• The semilunar canal contains ampulla.
• The vestibule contains otoliths.

Olfactory receptor嗅觉接受器
• Latin olfacere ‘to smell’
• located at the upper
nasal mucosa
• mainly composed of
hairy olfactory cells.
• A chemoreception that
forms the sense of
smell.
• Detect of hazards,
pheromones, and food

Quiz
• What is the purpose of the Olfactory System?
A. Recognise the things we eat
B. Sense of smell perceived by the brain
C. Recognise the things we see
D. Work out what we are hearing

Olfactory cells嗅觉细胞
• Ciliated with olfactory cilia嗅毛

Quiz
• The sense of smell is dependent on ______ cells.
A. optic
B. auditory
C. olfactory
D. proprioceptor
E. odiferous
There are many different types of olfactory cells
and the smell we perceive depends upon the
combination of olfactory cells that are stimulated.

Nasal lining. Coloured scanning electron micrograph (SEM) of the olfactory
epithelium that lines the nasal cavity, showing olfactory cells (green)
surrounded by numerous cilia (hair-like projection, brown).

Formation of smell
• Vaporized odor molecules
enter the nostrils and
dissolve in the mucus.
• The olfactory cilia is
stimulated.
• The olfactory cell generate
nerve impulse.
• The olfactory nerve
transmits the nerve
impulses into the brain.
• Smell (olfaction) is created.

Taste receptor
• Tongue is the taste organ.
• Papillae乳头突 (sg. Papilla) are found
on the surface on the tongue.
• Many taste buds味蕾 (taste
receptors) are found on the two
lateral sides of papilla.
• Taste buds are formed by a group of
taste receptor cells.
• Also a chemoreceptor.
Coloured SEM showing papilla.

Taste buds
Taste buds of circumvallate
papillae of the mature
cynomolgus (TEM observation)

Quiz
• Taste buds are located primarily on the ______.
A. upper palate
B. tongue
C. gums
D. turbinates of the nose
E. uvula

Quiz
• Taste buds are pockets of cells that ____________.
A. lie flat on the surface of the tongue epithelium
B. extend through tongue epithelium and open at a taste pore
C. lie along the walls of papillae
D. lack microvilli
E. all of the above

Formation of taste
• Saliva dissolves chemical
substances from the
food.
• The microvilli of the taste
receptor cells in the taste
buds are stimulated.
• Nerve impulse is
produced and
transmitted to brain
(gustatory cortex味觉皮层)
via gustatory nerve.

Quiz
• The _________ bear receptor proteins for certain molecules; when
molecules bind to these receptor proteins, nerve impulses are
generated in associated sensory nerve fibers that are interpreted in
the brain as tastes.
A. taste buds
B. thermoreceptors
C. taste pores
D. papillae
E. taste receptor cells

Receptors in skin
• Skin receptors
include touch,
heat, cold,
pressure, pain
and so on.

Quiz
• Skin contains receptors for ____________.
A. touch
B. pressure
C. pain
D. temperature
E. all of the above

Functions of skin receptors
Receptors Function(s)
Meissner’s
corpuscle
Touch
Ruffini’s
corpuscle
Pressurized touch
Pacinian
corpuscle
Pressure
Krause
bulbous
corpuscle
Cold
Free nerve
ending
Cold, heat and pain
Krause
bulbous
corpuscle
(cold)

Meissner’s Corpuscle
Krause bulbous
corpuscle
Ruffini’s corpuscle

Quiz
• The sense of fine touch is due to ___________.
A. Pacinian corpuscles
B. Meissner corpuscles
C. end-bulbs of Krause
D. Ruffini end organs
E. all of the above
The sense of fine touch is due to Meissner
corpuscles and Merkel disks. Pacinian corpuscles,
end-bulbs of Krause, and Ruffini end organs are
general pressure receptors.

Quiz
• Pain receptors ______________.
A. are highly specialized nerve endings
B. are free nerve endings
C. have unique neurotransmitters and neuron paths
D. are perceived independently from the brain
E. all of the above are true

Distribution of receptors
• Receptors are distributed unevenly
over the body.
• Finger, tongue, nose and lips all are
very sensitive towards touch.
• Foot pad, thigh and the back portion
of upper arm are least sensitive
towards touch.
• The front portion of upper arm has
numerous temperature receptors
which are sensitive to cold and heat.

Quiz
• Receptors for a particular sensation, such as touch, are spread evenly
throughout the skin surface.
A. True
B. False

Summary
• Smell is detected by the olfactory receptors in the nasal cavity.
• Taste is detected by the taste receptor cells of the taste buds on the
papillae of the tongue.
• Skin receptors detects touch, pressure, and temperature.
Receptors Function(s)
Meissner’s corpuscle Touch
Ruffini’s corpuscle Pressurized touch
Pacinian corpuscle Pressure
Krause bulbous corpuscle Cold
Free nerve ending Cold, heat and pain

TEM of Vestibule hair cells
Left: TEM image showing the normal ultrastructural appearance of
both types of vestibular hair cells in the fused anterior and lateral
cristae of the Ecl mouse. Vestibular hair cells have a characteristic
shape and innervation pattern, i.e., a flask-shaped type I hair cell (I)
surrounded by a typical chalice and a rod-shaped type II hair cell (II).
Inset: Detail of a cross-section of the apical surface of a hair cell
showing the normal appearance of the stereocilia and the kinocilium.
Scale bars = 10 μm, 1 μm in inset.

hair cells on the utricle
SEM image of the hair cells long microvilli
(hatched circles) on the utricle, revealing
long stereocilia (up to 5 µm in length)
partially surround a 9-µm kinocilium. (b)
TEM image through the elongate hair cells
and peripheral nerve bed. (c) The top of the
cell, buttressed by a long microvillus. cm,
cell membrane; cp, cuticular plate; hc, hair
cell; jc, junctional complex; lmv, long
microvilli; n, nucleus; ps, phagosomes; pnf,
peripheral nerve fibres; smv, short
microvilli.

AAV8 vector (Penn Vector Core) transduces vestibular
and cochlear hair cells with different efficiencies. (A)
Diagram of the mouse inner ear and viral injection
through the round window of the cochlea. The
vestibular sensory epithelia [AC, ampullar crista(e) of
the three semicircular canals; SM, saccular macula; UM,
utricular macula] and cochlear sensory epithelium (OC,
organ of Corti) are drawn in pink and in red,
respectively. Details of an AC and the OC are presented
on the left side and right side of this diagram,
respectively, with the hair cells (IHCs, OHCs, and VHCs)
drawn in red. The AAV8-Sans-IRES-GFP (Penn Vector
Core) recombinant virus injected through the cochlear
round window of a mouse on P2.5 transduces the vast
majority of VHCs (B, Upper) and transduces cochlear
IHCs and OHCs more efficiently in the apical region than
in the basal region of the cochlea (C, Upper), as shown
by the GFP labeling (green) on P8.5. All hair cells are
stained red by an anti-myosin VI antibody. Higher
magnification views of the AC (B, Lower) and the OC (C,
Lower) from the cochlear apical region are shown.
(Scale bars: Upper, 50 μm; Lower, 10 μm.)

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