The document discusses the human nervous system, detailing its structure and functions, which include controlling voluntary and involuntary actions. It also explains the sensory organs and their roles in detecting stimuli such as sight, sound, taste, smell, and touch, along with the mechanisms involved in these processes. Additionally, the document highlights the importance of these systems in maintaining homeostasis and responding to environmental changes.

1. CHAPTER 1 :
STIMULUS AND RESPONSE
SCIENCE FORM 3
BY TEACHER HAYATI, SIGS JB

2. 1.1 HUMAN NERVOUS SYSTEM

3. HUMAN NERVOUS SYSTEM
• The human nervous system is an
important control system in body
coordination.
• Other than sight, thinking and body
movement, the human nervous system
also controls and coordinates organ
functions in the body and maintains a
balanced internal environment through a

4. STRUCTURE OF THE HUMAN
NERVOUS SYSTEM
•Central Nervous
System
•Periferal Nervous
System

6. FUNCTIONS
OF THE
HUMAN
NERVOUS
SYSTEM
• The human nervous system
controls and coordinates
organs and parts of the body
by
• detects stimuli
• sends information in the
form
of impulses
• interprets impulses
• produces appropriate
responses

7. VOLUNTARY AND
INVOLUNTARY ACTIONS
•The responses of the human
body to stimuli can be divided
into voluntary actions and
involuntary actions.

8. VOLUNTARY ACTIONS
• Voluntary actions are conscious
actions and conducted under one’s
will.
• All voluntary actions are controlled
by the brain.
• Examples of voluntary actions
include reading, writing, speaking,
eating, drinking, walking, running
and exercising.

9. VOLUNTARY ACTIONS

11. INVOLUNTARY
ACTIONS
•Involuntary actions are
actions that occur
immediately
without conscious
control or prior
thoughts.
•Involuntary actions can be
classified into two.

12. INVOLUNTARY ACTIONS
Involving medulla
oblongata
• Heartbeat
• Breathing
• Peristalsis
• Secretion of saliva
Involving spinal cord (reflex
actions)
• Withdrawing hand
when it accidentally touches a
hot
object
• Withdrawing foot when it
accidentally
steps on a sharp object

13. INVOLUNTARY
ACTIONS
INVOLVING
MEDULLA
OBLONGATA

14. INVOLUNTARY
ACTIONS
INVOLVING
MEDULLA
OBLONGATA
Size of the pupil

15. INVOLUNTARY ACTIONS
INVOLVING SPINAL CORD
(REFLEX ACTIONS)

17. IMPORTANCE OF THE NETWORK OF
HUMAN NERVOUS SYSTEM IN DAILY
LIFE
• The network of the human nervous system controls and
coordinates the organs and parts of the body to carry
out processes in the body such as breathing and body
movements.
• A damaged nervous system normally causes a person
to become temporarily, partially or completely paralysed.
• For example, if the nerves in the muscles of a leg or hand
are injured, the person will face difficulty in moving his
leg or hand. In the case of a more serious problem, he
might have to depend on machines to carry out his
physiological processes such as breathing or heart
beating. Humans are blessed with a nervous system, so
they should use and take good care of it.

18. 1.2 STIMULI AND
RESPONSES IN HUMANS

19. STIMULI AND RESPONSES
IN HUMANS
• These changes are called stimuli.
• Examples of stimuli include light, sound
and
chemical substances.
• Humans use their sensory organs to
detect stimuli.
• Humans have five sensory organs: eyes,
ears, nose, skin and tongue

20. EYES

21. STRUCTURE OF HUMAN EYE
Ciliary muscles
Eye Lens
Iris
Pupil
Cornea
Sclera Choroid
Retina
Yellow spot
Optic nerve
Blind spot
Vitreous humour
Aqueous
humour
Suspensory
ligament

22. Front view of eye
Eyelid
Pupil
Sclera
Iris

23. Side view of eye

24. FUNCTION
- Allow light to enter the eye
- refracts and focuses light
onto the retina
CORNEA
-Transparent layer at the front
of the eye
- Curved shape

25. CONJUNCTIVA
- Thin transparent
membrane covering
the exposed part of
the eye

26. AQUEOUS HUMOUR
- Watery,
- transparent
fluid
- Fills the space
between cornea and
lens

27. FUNCTION
- Helps focus images on the retina
- Helps maintain the shape of the
eyeball

28. PUPIL
- A small opening in
the centre of the
iris

29. FUNCTION
•Enables light to
enter the eye
•Controls amount of
light entering the eye

30. IRIS
- Part of the choroid
layer which can be
seen from the front
of the eye as a disc-
shaped structure
- Consists of muscles
- Coloured, for
example, brown
green or blue

31. FUNCTION
•Controls the size of
the pupil thus controlling the
amount of light entering the
eye

32. CILIARY MUSCLE
- Consists of the
ciliary muscle
- Part of the
choroid layer

33. Contracts and
relaxes to
change the
thickness of the
lens
FUNCTION

34. SUSPENSORY
LIGAMEN
Consists of fibres
attaching the lens to
the ciliary body

35. EYE LENS
Transparent and
elastic convex lens
which focuses light
onto the retina

36. Vitreous humour
Transparent jelly-like
substance which
maintains the shape of
the eyeball and focuses
light onto the retina

37. SCLERA
Strong layer that maintains the shape of the eye and protects it

38. CHOROID
Black layer that prevents
reflection of light in the eye
and
supplies oxygen and
nutrients
to the eye

39. Layer containing
photoreceptors which
detects light and
produces
nerve impulses
RETINA

40. YELLOW SPOT
Part of the retina which
is most sensitive to light
as it has many
photoreceptors

41. BLIND SPOT
Part of the retina which is
not sensitive to light as
there are no
photoreceptors and
an exit point for
all optic nerve fibres.

42. OPTIC NERVES
Nerve fibres which carry nerve impulses from the retina
to the brain to be interpreted.

43. WHAT ISTHE COLOUR OFTHE
OBJECT SEEN?
• The retina has two types of photoreceptors: rod
cells and cone cells
• Rod cells are sensitive to different light intensities
including faint light but are not sensitive to the
colours of light.
• Cone cells are sensitive to the colours of light
under bright conditions.
• There are three different types of cone cells, with
each is sensitive to red light, green light and blue
light.

45. Mechanism of Sight

46. EAR

47. The Human Ear
Outer
- Pinna
- ear canal
(filled with
air)
- eardrum
Middle
- ossicles
- oval window
- Eustachian tube.
(filled with air)
Inner
-Cochlea
- semicircular
canals
- auditory nerve
(contain fluid)

49. EARLOBE
Collects and
directs sound
waves into the
ear canal

50. EAR CANAL
Directs sound waves
to the eardrum

51. EARDRUM
(THIN MEMBRANE)
Vibrates according to the
frequency of the sound
waves received and
transfers the vibrations to
the ossicles

52. OSSICLES
(made up of three small
bones)
Amplify sound vibrations
and transfer them to the
oval window

53. OVAL WINDOW
Collects and
transfers sound
vibrations from
the ossicles
to the cochlea

54. EUSTACHIAN
TUBE
Balances the air
pressure on both
sides of the
eardrum

55. COCHLEA
(contains fluid)
Detects and converts
sound vibrations into
nerve impulses

56. SEMI CIRCULAR
CANALS (contains fluid)
Detect the position of
the head and help to
balance thebody

57. HEARING MECHANISM

59. NOSE

62. STRUCTURE
OFTHE NOSE
• The nose is the sensory organ of
smell.
• Smells are chemical
substances present in the air.
• About 10 million sensory
cells for smell are located at the
roof of the nasal cavity

63. FUNCTION OF SENSORY
CELLS OF SMELL
• Sensory cells for smell are tiny and
covered with a layer of mucous.
• Chemical substances in the
air will dissolve in this layer of
mucous and stimulate the cells to
produce nerve impulses.
• The nerve impulses are then sent to
the brain to be interpreted to
determine the type of smell.

65. Chemicals
in the air
Air enters nasal
cavity through
nostrils
Chemicals
dissolve in the
mucus layer
Receptors
stimulated by the
chemicals
Receptors
(olfactory nerve)
send messages to
the brain
Brain interprets the
messages as a
specific smell
The detection of Smell

66. TONGUE

67. STRUCTURE OFTHETONGUE
• The tongue is the sensory organ of taste.
• There are tiny nodules known as papillae on
the surface of the tongue.
• The surface of a papillae is covered by hundreds
of taste buds.
• Each taste bud contains 10 to 50 taste
receptors.
• These taste receptors can detect five types
of basic tastes which are sweet, salty, sour,
bitter and umami

69. DIFFERENT AREAS OFTHETONGUE ARE
MORE SENSITIVETO SPECIFICTASTE
• Areas of the tongue are sensitive to all five
tastes.
• However, different areas of the tongue have
different sensitivities towards specific taste.
• For example, the area in front of the tongue is
more sensitive to sweet taste whereas the sides
are more sensitive to sour and salty tastes.
• The area at the back of the tongue is more
sensitive to bitter taste.
• The area at the centre of the tongue, however is
more sensitive to umami taste.

71. UMAMI
• Umami is classified as a basic taste because
there are taste receptors that can only detect
umami taste.
• This is the same as other basic tastes such as
sweet, salty, sour and bitter.
• Umami taste is related to delicious tastes such
as the taste of meat in soups or the taste of
fermented foods such as cheese and
mushrooms or monosodium glutamate (MSG).

72. FUNCTION OFTASTE BUDS
• When food is chewed, part or all the
chemical substances in the food dissolve in
the saliva.
• These dissolved chemical substances will
diffuse into the taste buds through their
pores and stimulate the taste receptors in
them to produce nerve impulses.
• These nerve impulses are then sent to the
brain to be interpreted as sweet, salty,
sour, bitter, umami tastes or a
combination of the basic tastes.

73. Chemicals in
food released
by chewing
Chemicals
dissolved by
saliva
Taste receptors
stimulated by
chemicals in saliva
Taste receptors
send messages to
the brain
Brain interprets
the messages as a
specific taste
Detection of Taste

74. SKIN

75. SKIN
• The skin is the largest
sensory organ in the
human body.
• The human skin is made
up of a thin outer layer
known as epidermis and
an inner layer known as
dermis.

76. The Structure of Human Skin
Three layers:
Epidermis Dermis
Hypodermis
(fat layer)

77. EPIDERMIS
• Outer layer of the skin.
divided into three layers.
• Outermost layer is made up of
dead cells.
• Tough and water-resistant .
• It also protects the sensitive cells
under it
• Prevents the entry of germs into
the body.

78. DERMIS
• Inner layer of skin.
• Blood vessels, glands and
receptors are found
• The glands ~sweat glands and
sebaceous glands.
• Receptors~ touch receptors,
pain receptors, heat receptors,
cold receptors and pressure
receptors.

79. HYPODERMIS
(FAT LAYER)
is a layer directly
below the dermis and
serves to connect the
skin to the fibrous
tissue of the bones
and muscles.

80. SKIN
• The skin has five types of
receptors at different
positions to detect different
stimuli.
• When the receptor in the skin
is stimulated, nerve impulses
are produced and sent
through
the nervous system to the
brain to be interpreted and to

81. Receptors in the Skin
1. Cold receptors
sensitive to cold.
2. Heat receptors
sensitive to heat.
3. Pain receptors
- nearest to the
epidermis.
- nerves endings. 4. Touch receptors
- sensitive to slight
pressure
- found more
abundantly in
certain parts
(fingertips).
5. Pressure receptors
- sensitive to pressure.
- located the furthest
from the epidermis.
- stimulated when any
object presses hard
against the skin.

82. SENSITIVITY OF THE SKIN ON DIFFERENT
PARTS OF THE BODY TOWARDS STIMULI
• The sensitivity of skin towards stimuli
depends on the number of receptors and
the thickness of the skin epidermis.
• For example, the tip of the finger is very
sensitive towards touch because at the tip of
the finger, there is a large number of touch
receptors and the epidermis is thin.
• The tongue, nose and lips are also very
sensitive to touch.
• The elbow, the sole of the foot and the back
of the body are less sensitive to touch.

84. LIMITATIONS OF SIGHT
• Limitation of sight is the
limitation in the ability of the
eye to see objects.
• We cannot see very tiny
objects such as
microorganisms as well as
very distant objects such as
planet Jupiter.
• Limitations of sight include
optical illusions and blind
spot.

86. OPTICAL ILLUSION
• Optical illusion occurs when
an object that is seen differs
from
its actual state.
• Optical illusion occurs because
the brain is unable to
accurately interpret the object
seen by
the eye due to distractions
around theobject.

87. OPTICAL ILLUSION

88. OPTICAL ILLUSION

89. OPTICAL ILLUSION

90. OPTICAL
ILLUSION

91. OPTICAL
ILLUSION

92. OPTICAL
ILLUSION

96. BLIND SPOT

97. BLIND SPOT
We are unaware of the presence of the blind spot in the eye
because it is not possible for theimage of the same object to fall on
the blind spots of both eyes simultaneously. Carry out the following
simple activity to investigate the blind spot.

98. Various devices used to overcome the limitations of
sight.
-ELECTRON MICROSCOPE

99. TELESCOPE

100. LIGHT
MICROSCOPE

101. BINOCULAR

102. X-RAY
MACHINE

103. ULTRA SOUND
MACHINE

104. TASK
Gather information on the use
of these devices from the
Internet, magazines, books,
newspapers and other sources.
Present the findings using
multimedia presentation.

105. EYE DEFECTS
Defects of vision:
(a) short
sightedness.
(b) long
sightedness.
(c)
astigmatism.
In normal vision, light is focused accurately on the
retina to form an image on the retina.This will
produce a clear and sharp image on the retina.

106. A SHORT
-SIGHTED PERSON
1. Can see nearby objects clearly but distant objects appear blur
due to the image of the object which falls in front of the
retina.
2. The eyeballs are too long and the eye lenses are too thick.
This is because the ciliary muscles are too weak to make the
eye lens thinner.
3. Can be corrected by wearing concave lenses.

109. CONCAVE LENSES

110. A LONG-SIGHTED PERSON
1. Can see distant objects clearly but nearby objects appear
blur because the image of a near object falls behind the
retina.
2. The eyeballs are too short and the eye lenses are too
thin.This is because the ciliary muscles are too weak to
make the eye lens thicker.
3. The defect can be corrected by wearing convex lenses.

113. CONVEX LENSES

114. ASTIGMATISM
Caused by irregular curvature of the cornea or the lens.
The light rays from an object is split and focused at different
points in the eye.
Some light may be focused on the retina, some light will be
focused in front or behind the retina.
Causes blurred vision for both near and distant objects
Can be corrected with cylindrical lenses

119. LIMITATIONS
OF HEARING
• Limitations of hearing are limitations in
the ability of the ear to hear sound.
• We can only hear sounds of frequencies
between the range of 20 Hz to 20 000 Hz.
• The ears are unable to detect sounds
which lie outside this frequency range.
• The frequency range of hearing of every
individual is different.
• When a person gets older, the frequency
range
of his hearing gets narrower as his
eardrum becomes less elastic.

120. FIRST
STETHOSCOPE
• The first stethoscope made of
wood was invented by Rene
Laennec at Necker-Enfants
Malades Hospital, Paris in 1816.

121. Stethoscope helps us to
listen to the
heartbeats.

122. Stethoscope

123. A loudspeaker amplifies
sound so that it can be
heard
from far away.

124. LOUD SPEAKER

125. MICROPHONE

126. DEFECTS OF
HEARING
• Defects of hearing occur when the
sense of hearing of a person does
not function well.
• Defects of hearing are normally
caused by damage to the ear due
to infection by microorganisms,
injury, ageing process or
continuous exposure to loud
sounds.

127. FACTORS OF
HEARING DEFECT

128. WAYS TO CORRECT THE HEARING DEFECT
• Damages to the outer ear and middle ear can be
corrected easily. For example, the clearing of
foreign objects in the ear canal.
• Punctured eardrum and damaged ossicles can also
be corrected using medicine or surgery.
• Damage to the inner ear is more difficult to
correct.
• A damaged cochlea can be corrected using a
cochlear implant but a damaged auditory nerve
cannot be corrected using medicine or surgery.

131. HEARING AID

132. 1.3 STIMULI AND RESPONSES IN
PLANTS

133. STIMULI AND
RESPONSES IN
PLANTS
• Like humans and animals, plants
can also detect stimuli and
respond to them.
• The stimuli that can be detected
by plants include light, water,
gravity and touch.
• The responses of plants can be
divided into two which is tropism
and nastic movement

134. TROPISME
• Tropism is a directional response of plants to stimuli
such as light, water, gravity and touch coming from a
certain direction.
• A certain part of a plant will grow towards or move away
from
the detected stimulus.
• The part of a plant which grows towards a stimulus is
known as positive tropism whereas the part of a plant
which grows away from a stimulus is known as negative
tropism.
• The directional response of plants normally occurs
slowly and less significantly.

135. PHOTOTROPISM
• Phototropism is the response of plants towards
light.
• Shoots of plants show positive phototropism
which is growth towards the direction of light
• As plants need light to carry out photosynthesis,
positive
phototropism ensures that shoots and leaves of
plants obtain enough sunlight to make food
through photosynthesis

137. HYDROTROPISM
• Hydrotropism is the response of plants towards
water.
• Roots of plants show positive hydrotropism
which is growth towards the direction of water
• Positive hydrotropism allows roots of plants to obtain
water to carry out photosynthesis and absorb
dissolved mineral salts to stay alive.

139. GEOTROPISM
• Geotropism is the response of plants towards
gravity.
• Roots of plants show positive geotropism
which is
downward growth towards the direction of
gravity.
• Positive geotropism allows the roots of plants
to grow
deep into the ground to grip and stabilise the
position
of the plant in the ground.
• On the other hand, shoots of plants show
negative geotropism which is upward growth
in the opposite direction of gravity.

141. THIGMOTROPISM
• Thigmotropism is the response towards
touch.
• Tendrils or twining stems show positive
thigmotropism when they cling onto
whatever objects or other plants they
come into contact
• This response enables plants to grow
upwards to obtain sunlight and grip
objects to obtain support.
• Roots show negative thigmotropism
since they avoid any object that obstructs

142. THIGMOTROPISME

143. NASTIC
MOVEMENT
• Nastic movement is the response
towards a stimulus such as touch
but does not depend on the direction
of the stimulus.
• Nastic movement occurs more
rapidly than tropism. For example,
the Mimosa sp. responds to touch by
folding its leaves inwards when
touched as shown in Photograph
1.21.
• This nastic movement serves as a
defence of the Mimosa sp. against its
enemies and strong wind.

144. NASTIC MOVEMENT

146. 1.4 IMPORTANCE OF RESPONSES
TO STIMULI IN ANIMALS

147. STEREOSCOPIC
VISIONS

149. MONOCULAR VISIONS

152. STEREOPHONIC HEARING
• Stereophonic hearing is hearing using both ears.
• Stereophonic hearing allows us to determine the
direction of the sound accurately.
• The importance of stereophonic hearing to humans is
to determine the location of a source of sound.
• Stereophonic hearing helps predators to determine
the location of their prey.
• Conversely, stereophonic hearing also helps prey to
determine the location of their predators and to
escape from them.

153. HEARING
FREQUENCIES
OF ANIMALS

154. SENSORY ORGANS
ENSURE THE
SURVIVAL OF
ANIMALS ON
EARTH
Secretion of
pheromone

155. LATERAL LINE

156. Producing electric field

157. TASK