Download 15.4 Structure and functions of the eye

15 Detecting environmental conditions
•
15.1 Irritability
•
15.2 The five senses
•
15.3 The eye
•
15.4 Structure and functions of the eye
•
15.5 The control of the amount of light entering the eye
•
15.6 The accommodation of the eye
•
Mind Map
15.1 Irritability
Irritability
15.1 Irritability
Irritability
Ability
senses our
surroundings
responds to
surroundings
15.1 Irritability
Body
Part B
Running
Lion is coming
Part C
Part A
15.1 Irritability
Body
Central
Nervous
Part
B
System
(CNS)
Running
Nerve
Lion
is coming
Stimulus
Nerve
Part A
Receptor
Response
Part C
Effector
15.1 Irritability
Receptor
Stimuli
CNS
Effector
Response
15.1 Irritability
Receptor
Stimuli
Nerve
CNS
Nerve
Effector
Response
15.1 Irritability
A change in
External
environment
Pressure, touch, pain,
movement of air, heat,
cold, light, sound,
chemicals substances
Stimuli
Internal
environment
Blood pressure,
water potential and
CO2 conc. in blood,
tension in muscles
15.1 Irritability
Receptor
Stimuli
Nerve
CNS
Nerve
Effector
Response
15.1 Irritability
Stimulus
1 stimulates
Receptors
Interpret as
sensation
Receptor
Central
2
Nervous
produces
nerve impulses System
Nerve
(CNS)
15.1 Irritability
Stimulus
Receptors
1
Detect stimuli
2
produce nerve
impulses
15.1 Irritability
Stimulus
Sensation
Light
Sight
Sound
Hearing
Chemicals in air
Smell
Chemicals in food
Taste
Change in temp.
Touch
Pressure
Pain
Heat or cold
Texture
Pressure
Pain
15.1 Irritability
Receptor
Stimuli
Nerve
CNS
Nerve
Effector
Response
15.1 Irritability
Gland
Secretion
2
Muscle
Muscle
contraction
1
Effector
Response
15.1 Irritability
Behaviour
Lower animals
Innate
Higher animals
Same stimulus
with different responses
Modified by learning
15.2 The five senses
Five senses
15.2 The five senses
Sight
Hearing
Taste
Smell
Touch
15.2 The five senses
2
Touch
receptor
3
Cold
receptor
4
Heat
receptor
1
Pain
receptor
What kinds of receptor are
found in the skin?
Touch
Skin
Pressure
5
receptor
15.2 The five senses
Distribution
of receptors
Uneven
Touch
Skin
Even
15.2 The five senses
Sight
Hearing
Taste
Smell
Touch
15.2 The five senses
Taste
Taste bud
Tongue
15.2 The five senses
Taste
Epithelium
Soluble
chemicals
in food
Gives the
sensation of
taste
Brain
15.2 The five senses
Four basic taste
sensations
Sourness
Saltiness
Taste
Bitterness
Sweetness
15.2 The five senses
Sight
Hearing
Taste
Smell
Touch
15.2 The five senses
Nose
Smell
Upper
epithelium
Nasal cavity
15.2 The five senses
Smell
Upper
epithelium
Mucus
Nasal cavity
15.2 The five senses
Brain
Smell
Gives sensation of smell
Smell
receptor
Mucus
Soluble chemicals
in gas
Air
15.2 The five senses
Smell
Nose
Detects
soluble
chemicals
Sense
Tongue
Taste
2
Detects
harmful
substances
Stimulates
appetite
Initiates secretion of
3
digestive juices
1
Flavour of food
15.2 The five senses
Sight
Hearing
Taste
Smell
Touch
15.2 The five senses
Hearing
Middle
Ear
Outer
Ear
Ear
Inner
Ear
15.2 The five senses
Hearing
Pinna collects
the sound wave
Passes along
auditory canal
Pinna
Auditory
Eardrum
canal
Air vibration
Strikes on the
eardrum
Result
Eardrum
vibrates
15.2 The five senses
Hearing
Vibration of
ear bones
Transmittion
of vibration
Eardrum
Ear
bones
Oval window
Oval
window
15.2 The five senses
Hearing
Sensory hair cells
are stimulated
Vibration of fluid
in cochlea
Auditory
nerve
Nerve impulses
are produced
Auditory nerve
transmits impulses
Cochlea
Oval window
15.3 The eye
The Eye
15.3 The eye
Tear gland
Eye muscles
Optic
nerve
Eye ball
Skull
15.3 The eye
For
protection
Skull
15.3 The eye
Eye muscles
Contract or relax
the eye can be
rotated
15.3 The eye
Transmits
impulses to the
brain
Optic
nerve
15.3 The eye
Tear gland
Tears
Keep the
eyes moist
Kill germs
15.4 Structure and functions of the eye
Structure &
functions of
15.4 Structure and functions of the eye
Wall of
eyeball
15.4 Structure and functions of the eye
Three layers
in the wall of eyeball
1
Sclera
2
Choroid
3
Retina
15.4 Structure and functions of the eye
Tough
1
Keeping the
shape of eyeball
2
Sclera
Protection
For muscle
attachment
3
15.4 Structure and functions of the eye
Internal
reflection
of light
Choroid
15.4 Structure and functions of the eye
Internal
reflection
of light
Absorbs light
Black pigment
Choroid
15.4 Structure and functions of the eye
Supply nutrients and oxygen to the eyeball
Contains
blood vessels
Choroid
15.4 Structure and functions of the eye
Walls of
eyeball
15.4 Structure and functions of the eye
Conjunctiva
protects
Cornea
15.4 Structure and functions of the eye
Allows light to pass
1
transparent
Light
Refraction of light
2
curved
Cornea
15.4 Structure and functions of the eye
15.4 Structure and functions of the eye
Cornea
is continuous with
Sclera
15.4 Structure and functions of the eye
Lens
Suspensory
ligament
Ciliary
muscle
15.4 Structure and functions of the eye
For focusing
Lens
15.4 Structure and functions of the eye
Change the thickness of the lens
Change the tension of
suspensory ligaments
Relaxes
Or
Contracts
Ciliary muscle
For
focusing
15.4 Structure and functions of the eye
Controls the amount of
light entering the eye
Pupil
Iris
Controls the size of pupil
15.4 Structure and functions of the eye
1 Help in refracting light
2 Maintain the shape
of the eyeball
Aqueous
humour
Diffusion of food
and oxygen to the
lens and the cornea
Vitreous
humour
3
15.4 Structure and functions of the eye
Retina
Sclera
Choroid
Retina
15.4 Structure and
functions of the eye
Sclera
Choroid
Retina
Light
Cone
Rod
Light-sensitive
cells
Optic nerve
15.4 Structure and
functions of the eye
How do you perceive
the colours?
Cone
Three types of cones:
blue cones
green cones
red cones
15.4 Structure and
functions of the eye
How do you perceive
the colours?
Cone
If blue light strikes
on blue cones,
blue colour can be
perceived.
It is the same for red
cones and green cones
15.4 Structure and
functions of the eye
15.4 Structure and functions of the eye
How do you perceive the colours?
Blue cone
Green cone
Red cone
+
-
-
Blue
-
+
-
Green
-
-
+
Red
+
+
+
White
-
-
-
Black
All colours in between are produced by stimulation of
various combinations of the different types of cones
15.4 Structure and
functions of the eye
Rod
It is sensitive to light
of low intensity
for dim light vision
15.4 Structure and functions of the eye
Yellow
spot
Blind spot
15.4 Structure and functions of the eye
Clearest image
detection with
greatest colour
discrimination
The density of
cones is the highest
in the yellow spot
Yellow
spot
No rods
present
15.4 Structure and functions of the eye
No image can be
detected
No
photoreceptors
A point that optic
nerve leaves the
eyeball
Blind spot
15.4 Structure and
functions of the eye
Not enough vitamin A in diet
No visual
purple
formation
Difficult to
see in the
dark
Rod
contains visual purple
for dim light vision
Night
blindness
15.4 Structure and functions of the eye
Image formation
and eye
accommodation
15.4 Structure and functions of the eye
Light rays reflected from an
object pass through cornea,
aqueous humour, lens and
vitreous humour
15.4 Structure and functions of the eye
Image formed is real, upside down
and smaller than the object
Image
15.4 Structure and functions of the eye
Image
Image is detected
by rods & cones
on retina
Nerve impulses
are produced
15.4 Structure and functions of the eye
Image
Impulses pass along
the optic nerve to
the cerebrum for
interpretation
Vision is
produced
cerebrum
15.4 Structure and functions of the eye
Experiment 15.1
To dissect and examine an ox’s eye
1. Obtain an ox’s eye from a
butcher.
2. Examine the eye muscles
and the optic nerve.
3. Remove the fat from the
back of the eye.
15.4 Structure and functions of the eye
Experiment 15.1
To dissect and examine an ox’s eye
4. Cut through the cornea at right angles. Pick up
the flaps of the cornea and examine the iris.
15.4 Structure and functions of the eye
Experiment 15.1
To dissect and examine an ox’s eye
5. Cut through the iris and
into the sclera to about
half-way around the walls
of the eye. Examine the
inner parts of the eye.
15.4 Structure and functions of the eye
Experiment 15.1
To dissect and examine an ox’s eye
6. Remove the lens. Place it on a piece of paper. Observe
the words underneath. Then press the lens to feel its
elasticity and observe the words through the lens again.
What changes do you observe?
7. Remove the vitreous
humour. Identify the
blind spot.
15.5 The control of the amount of light entering
the eye
15.5 The control of the amount of light entering
the eye
Pupil
Iris
Circular Radial
muscles muscles
15.5 The control of the amount of light entering
the eye
Under bright light
Circular muscles contract
and radial muscles relax
The size of pupil becomes smaller
Prevents photoreceptors on retina
from being over-stimulated
15.5 The control of the amount of light entering
the eye
Under dim light
Circular muscles relax
and radial muscles contract
The size of pupil becomes larger
Allows more light to pass through
the lens to form a clearer image
15.6 The accommodation of the eye
15.6 The accommodation of the eye
Lens
Compare the
two figures
In figure A,
A
Focal
length
* Thicker lens
* Shorter focal length
B
15.6 The accommodation of the eye
The ability of the eye
to adjust the thickness of the lens
for viewing near & distant objects
is called accommodation
15.6 The accommodation of the eye
Near object
3. Lens becomes thicker
2. The tension of suspensory
ligament is reduced
1. Ciliary muscles contract
15.6 The accommodation of the eye
Distant object
3. Lens becomes thinner
2. The tension of suspensory
ligament is increased
1. Ciliary muscles relax
15.6 The accommodation of the eye
Summary
Near object
Distant object
Ciliary
muscles
Contract
Relax
Suspensory
ligaments
Tension
decreases
Tension
increases
Lens
Thicker
Thinner
15.6 The accommodation of the eye
15.6 The accommodation of the eye
Distant
Near or Far
object ?
object
but not
clear
Short sight
because the image cannot be
focused onto the retina
15.6 The accommodation of the eye
Correction
Wearing
concave lens
Short sight
15.6 The accommodation of the eye
Correction
Long Sight
Wearing
convex lens
Near
object
cannot see the near object clearly
15.6 The accommodation of the eye
If a certain type of cone is missing,
certain colours may not be distinguished
Common type is red-green colour
blindness
It is a hereditary disease
Detecting of
environmental conditions
is called
irritability
stimulus
detected by
nerve
impulses
sent to
brain or
spinal cord
examples
include
hearing
taste
sight
smell
touch
sense organ
sense organ
sense organ
sense organ
sense organ
ear
tongue
eye
nose
skin
1. aqueous
humour
5. sclera
6. cornea
2. vitreous
humour
3. retina
produce
response
common
eye defects
structures include
to
effectors
include muscles
and glands
mainly by
five senses
change in external or
internal environment
is called
receptors
Mind Map
1. circular
muscles
7. choroid
8. lens
9. iris
4. optic
nerve
consists of
10. pupil
2. radial
muscles
for
controlling the
size of pupil
1. long sight
2. short sight
3. colour
blindness