CHAPTER 1: THE WORLD THROUGH OUR SENSES
1.1 Sensory Organs and Their Functions
Sensory Organs and Their Stimuli
1. Humans being have five main sensory organ, which are skin, nose, tongue, ears and eyes.
2. Sense detects stimuli, that is changes in surroundings (around us). 3. Five senses: i. sight
v . smell
4. Senses are part of the body called sensory organs.
5. Changes or object that can detect by our senses are called stimuli. 6. The ability of the sensory organs to detect stimuli is called senses. 7. All the sensory organs are complete with sensory receptors, that is the nerve endings that can detect stimuli.
Stimuli Sense Sensory organ
Light(Brightness, colour) Sight Eye
Sound Hearing Ear
Touch, heat, cold, pain, pressure Touch Skin
Sweet, sour, bitter, salty Taste Tongue
Smell or odors Smell Nose
The World through our
senses Light and sight Sound and hearing Stimuli and responses in plants
Properties of light
Properties of sound
Reflection and absorption
Nastic movement (move
run away) Science Form 2 note 2012 Laman web.
1.2 The Pathway from Stimulus to Response PMR 05
Figure 1.2 The summary of the pathway from stimulus to response 1. Our sensory organs are used to detect stimuli (Singular: stimulus). A stimulus is anything that causes a reaction in a living organism, e.g. Pain, heat, sound, chemicals.
2. When a stimulus is detected, receptor cells in the sensory organ will be triggered and generate impulses.
3. These impulses will be transmitted through the nerve and than to the brain.
4. The brain will further process and interpret the impulse signals as specific information than the organism has to respond to.
5. This information is than sent back to the sensory organ through the nerve to provide responses.
Stimulus → Sensory organ → Nerves → Brain → Nerves →Response Stimulus
Response Science Form 2 note 2012 EXERCISE
Sense of Touch PMR 07
Go to www.brainpop.com/health/integumentary/skin/index.weml Watch a movie on the skin. For easy access, go to www.icd.com.my 1. The sense of touch is the sense that is sensitive towards the touch stimulus provided by specific objects.
2. Organ involve in the detection of touch stimulus is the skin. 3. Structure of human skin:
a) The skin divided into three layer epidermis, dermis, fat layer (subcutaneous layer @ adipose layer @ fat layer)
b) Receptors are cell in our body that detected stimuli.
c) Our body have different types of receptors. These are:
i. pain receptor
ii. touch receptor
iii. heat receptor
iv. cold receptor
v. pressure receptor
1 Eye 2 Tongue 3 Ear 4 Nose 5 Skin
Detected by sense of
touch Science Form 2 note 2012 d) The pain receptor is in the epidermis.
e) The touch, heat and cold receptors are in the dermis. The pressure receptors are in the fat layer.
f) Each type of receptor can...