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1. 1.1 Sense Organ and Their Functions
1. Living organisms have sense organ.
2. These sense organs help us to detect changes in environment.
3. Different sense organs will detect different stimuli.
4. Stimuli are changes that occur in environment.
5. Senses are the ability of sense organs to detect stimuli.

4. a. The skin detect touch, pressure, heat or cold
b. The nose detect smell
c. The ear detect sound
d. The eye observes by seeing
e. The tongue detect taste

5. 5 different type
of senses in human

6. The relation between the stimuli, the five senses and
sense organs.
Activity Sense Sense
organ
Stimuli
a. Touch Skin Cold
b. Smell Nose Chemical
c. Taste Tongue Chemical
d. Hearing Ear Sound
e. Sight Eye Light

7. Eye
- Sensitive to light
Ear
- Sensitive to sound
Tongue
- Sensitive to
chemicals in
food and
liquids (taste)
Skin
- Sensitive to
touch
Nose
- Sensitive to chemical
in the air (smell)

8. Respond to stimuli

9. Response to stimuli
1.When stimulus is detected by a
sense organ, information is sent
to the brain.
2. A suitable response will then
be produced.
3. The brain is the control centre
that control all the action.
4. The brain is linked to all parts
of body by nerves.

10. 5. Nerve send signals to brain
when get response.
6. Nerve send signals from
sense organ to brain.
7. When the brain get message it
will interpret and produce a
suitable respond

11. Stimulus Sense organ Nerve Brain
NervesResponse
Skin nerve
Brain nerve

12. Structure and function of the eyes

13. Structure and function of the eyes
Cornea – refracts light
Iris – controls how much light enters pupil
Lens – focuses light onto retina
Retina – contains light receptors, some sensitive to light of
different colours
Optic nerve – carries impulses to the brain

14. • 3 layered of eyes wall
i. sclera (tough, outer layer)
ii. choroids (black, middle layer)
iii. Retina (innermost layer of the eye)
• The structure of the pupil is adapted to sense light. The
amount of light which enters the eye must be carefully
controlled for the eye to function properly.
This achieve through altering the pupil.
• in bright places – pupil smaller, iris bigger
• in dark places – pupil bigger, iris smaller

15. The Pupil reflex
• The role of iris and pupil is to regulate the
intensity of light that reaches the sensitive
retina
• Circular muscle – arranged around the
pupil
• Radial muscle – run outwards from the
pupil

17. In bright light
•The circular muscle contract
•The radial muscle relax
•The pupil constricts(narrows)
•Less light is able to reach the
retina to avoid damage

18. In dim light
•The radial muscle contract
•The circular muscle relax
•The pupil dilates (widens)
•More light is able to reach the
retina

19. The Formation of Images
How do we see?????????
1. Light rays travel
from the object
to eye
2. The light rays pass through the
eye, they are refracted by some
cornea, aqueous humour,
lens and vitreous humour 3. An upside down
image (flag) is
formed on the retina
4. The photoreceptors on
the retina send nerve impulses
along the optic nerve to the brain
5. The brain interprets the impulses and allows
us to see the object

20. ACCOMODATION
OF EYES
WHEN FOCUSING ON FAR AND NEAR
OBJECTS

21. Object
Eye lens
Cornea
Pupil
Retina
Image
Nerve
to brain

25. DISTRIBUTION OF RODS AND
CONES IN THE RETINA

26. The rod and cone cells in the
retina
Rods and Cones - Cells which are sensitive to light
•Rod cells – responsible for night visions
- respond to light of low intensity
- located mainly around the periphery of
retina
•Cone cells – responsible for colour vision
- only respond to light of high intensity
- most of the cones in the fovea
- 3 types of cone – sensitive to different
wavelength

30. Accomodation
The changes that occur in the eye when focusing on
far and near objects.
•Focusing – As light enters the eye, it must be
refracted (bent). So that we can see the image clearly
•The ciliary muscles, suspensory ligament and lens
are involved in accomodation in the eye

31. Looking at a distant object
• The ciliary muscle relax
• The pressure inside the eye pulls the
suspensory ligaments tight (taut)
• The lens is pulled into an elliptical (thin)
shape

32. Lens become thinner
Light from
Distant object
LOOKING AT A DISTANT OBJECT

33. LOOKING AT A NEAR OBJECT
• The ciliary muscle contract to counteract the
pressure inside the eye
• The suspensory ligament are not pulled and
become slack
• Lens become more spherical (fatter)

34. LOOKING AT A NEAR OBJECT
Lens become thicker
Light from
Near object