The World through Our Senses 1.1 Sensory Organs 1.2 Sense of Touch 1.3 Sense of Smell 1.4 Sense of Taste 1.5 Sense of Hearing 1.6 Sense of Sight 1.7 Light and Sight 1.8 Sound and Hearing 1.9 Stimuli and Responses in Plant Teacher Nurul
1.1 Sensory Organs Sensory Organs and Their Stimuli How do we know what is going on around us? Humans have five senses. help us to detect objects and the changes in the surroundings. Our five senses are the sense of sight, smell taste hearing sight touch
1.1 Sensory Organs Sensory Organs and Their Stimuli Sensory organs Stimuli Found in parts of the body Changes/ objects that can be detected by our senses Let’s go to the garden!
1.1 Sensory Organs Name the sense and the sensory organ in each of the photographs.
1.1 Sensory Organs Stimuli Sense ( deria ) Sensory organ Touch, heat, cold, pain & pressure Cold Skin Smell or odours Chemical Nose Sweet, sour, bitter & salt Chemical Tongue Sound Sound Ear Light (brightness or colour) Light Eye
1.1 Sensory Organs response The way in which a living thing acts upon receiving a stimulus <ul><li>How would you respond when you: </li></ul><ul><li>hear the bell ring? </li></ul><ul><li>eat hot and spicy food? </li></ul><ul><li>(d) smell a marigold, a foul smelling flower? </li></ul><ul><li>(e) see an empty plastic bag lying on the floor in front of you? </li></ul>
1.1 Sensory Organs Stimulus Receptors in Sense organ Nerves Brain Nerves Response Pain response Skin nerve Brain nerve Effectors (Muscles, glands)
1.1 Sensory Organs The Pathway from Stimulus to Response
1.2 Sense of Touch The organ that detect touch sense is skin. Skin give respond to stimuli like touch, pain, heat, cold and pressure. Our skin is 2mm thick and consists of 2 layers which epidermis and dermis. The sensitivity of the skin depends on the number of sensory receptors and the thickness of the epidermis.
1.2 Sense of Touch Epidermis (upper layer) <ul><li>made of dead cells </li></ul><ul><li>waterproof </li></ul><ul><li>act as a protective layer to </li></ul><ul><li>preventing the entry of bacteria </li></ul><ul><li>into the tissues. </li></ul>Dermis (lower layer) Consists of living cells, blood capillaries, nerve and sweat glands Consists receptor or nerve ending, enable skin to detect stimuli
1.3 Sense of Smell Nose is the sensory organ of smell . Sensory cells are found in the upper roof of the nose cavity. Smell from chemical substances dissolves in the mucus of the nose. Mucus in the nose stimulates the sensory cells of smell and sends impulses to the brain through nerve cells.
1.3 Sense of Smell Air Sensory cells Nasal cavity Nostril
1.3 Sense of Smell How do our nose detect smell???... Smells are carried by certain chemicals in the air. When we breathe, these chemicals go through our nose. It will then dissolve in mucuos – the moisture layer that covers the smell receptors on the upper part of the nose. The dissolved chemicals stimulate the smell receptors . The stimulated smell receptors then send messages to the brain. The brain identifies the smells. touch smell taste hearing sight
1.3 Sense of Smell Chemical substance Smell reseptors dissolve in mucus Nerves Brain (interpret the massage) Nerves Smell is identified
1.4 Sense of Taste The tongue is the sensory organ of taste . Our tongue able to detect and differentiate different taste such as sweet, salty, sour and bitter.
1.4 Sense of Taste When we eat or drink, foods or drinks dissolved in saliva are detected by the taste receptors in our tongue. On the surface of tongue has groups of sensory cells called taste buds for detecting different tastes. Different areas of the tongue are more sensitive to specific tastes.
1.4 Sense of Taste bitter sour sour salty salty sweet
1.4 Sense of Taste Chemical substance (food) Taste reseptors dissolve in saliva Nerves Brain (interpret the massage) Nerves Taste is identified
1.4 Sense of Taste All our senses work together, but the sense of smell and taste are special partners. When we eat, our nose smells the food and our tongue gives us the taste of the food. Together, they help us to sense most, if not all, of the flavors contained in the food we eat. Will the food taste as good as it normally does when our nose is blocked?
1.4 Sense of Taste It difficult to taste the food you eat when you get a flu.
1.5 Sense of Hearing Ear is the sensory organ of hearing. Our ear has 3 main parts: a. the outer ear , filled with air b. the middle ear , filled with air c. the inner ear , filled with liquid
1.5 Sense of Hearing Outer ear Middle ear Inner ear
1.5 Sense of Hearing pinna ear cannal eardrum ossicles coclea Eustachian tube auditory nerve semicircular canals oval window
1.5 Sense of Hearing Part of ear Structure Functions Pinna Made of cartilage and skins. Shape like a funnel Collects and directs sounds into the ear canal Ear canal A long tube, lined with hairs Directs sounds to the eardrum Eardrum A thin membrane Vibrates when sound waves hit it Ossicles Three small bones Amplify vibrations and transfer them to the oval window Oval window A small, thin membrane Transfers vibrations of the ossicles to the cochlea Cochlea A coiled tube, filled with fluid. Contains receptors Detects vibrations and converts then into nerve impluses Eustachian tube A tube that connects the middle ear to the throat Equalises air pressure on both sides of the eardrum, preventing it from damage Auditory nerve Nerve fibers that connect to the brain Cariies nerve impulses to the brain Semicircular canals Three semicircular canals situated at right angles to each other Detect position and movement of head to help us keep our balance
1.5 Sense of Hearing Pinna get sound Auditory canal Eardrum vibrate Ossicles vibrate Oval window Liquid in cochlea vibrate Sound waves Auditory nerve
1.8 Sound & Hearing Sound produced by vibrations of an objects . When sound is produced kinetic energy is changed to the sound energy. Sound can travel through solids , liquids and gases . Sound cannot travel through vacuum . Sound travels faster trough solids than liquids or gases because the particles in a solid are very close together.
1.8 Sound & Hearing Sound can be absorbed by a soft surface such as soft board on the walls of a cinema hall. Soft and rough surfaces are good absorbers of sound. Sound can be reflected when sound hits hard and smooth surfaces like walls. A reflected sound is called an echo. A large tunnel and a cave are examples that can give out echoes.
1.8 Sound & Hearing Defects of hearing and ways to correct them Hearing loss can be occur from wax blockage, a punctured eardrum, birth defects or ear infections. The damage is often temporary and can be treated medically or surgically.
1.8 Sound & Hearing Defects of hearing and ways to correct them Other hearing loss can be caused by the processes of aging, bacterial infections, a severe blow to the side of the head, extended exposure to loud sound or a tumour in the inner ear. This damages cannot be treated medically but can be corrected using hearing aids.
1.8 Sound & Hearing Limitations of hearing Our ears can only hear sounds which have a frequency of about 20 Hz to 20 000 Hz. Different people have different ranges of hearing. Some devices that are used to overcome the limitations of hearing such as earphones and stethoscopes.
1.8 Sound & Hearing Stereophonic hearing Stereophonic hearing is hearing with both our ears. Stereophonic hearing helps us to determine the direction from which a sound comes.
1.6 Sense of Sight The eye is the sensory organ of sight and it is sensitive to light . Human beings have a pair of eyes situated in the socket of the skull. Each eye is surrounded by fatty tissues.
1.6 Sense of Sight Light enter the eye through the cornea and aqueous humour to the pupil and to the lens of the eye. The convex lens focusses the light rays onto the vitreous humous and the retina to produce a clear image. cornea aqueous humour pupil lens vitreous humous retina optic nerve
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
1.7 Light & Sight Light plays an important part in our life because without light we cannot see. The properties of light are: (a) its travels in straight lines. (b) its can be reflected. (pantul) (c) its can be refracted. (bias)
Properties of Light Light travels in a straight line Light can be reflected Light can be refracted Light can be dispersed
1.7 Light & Sight Light travels in straight lines . This causes the formation of shadows and eclipses of the sun and the moon.
1.7 Light & Sight Light can be reflected . The image in a plane mirror is due to the mirror reflecting light from the object to the observer. This is because the light bounces off the surface of an object. A smooth and shiny opaque surface reflects more light than a rough surface.
1.7 Light & Sight The image in a plane mirror the angle of reflection = the angle of incidence
1.7 Light & Sight When light travels from one medium to another, its speed changes. This causes the light to bend or change its direction means the light is refracted .
1.7 Light & Sight When light ray travels from a less dense medium (air) to a more dense medium (glass) the refracted ray bends towards the normal . mirror air ray normal
1.7 Light & Sight When light ray travels from a more dense medium (glass) to a less dense medium (air) the refracted ray bends away from the normal . mirror air ray normal
1.7 Light & Sight When light ray travels medium perpendicularly the light ray passes straight through the medium without being bent or refracted. mirror air ray normal air
1.7 Light & Sight A stick which partly immersed in water to appear bent at the surface of the water.
1.7 Light & Sight <ul><li>Defects of vision and ways to correct them </li></ul><ul><li>People who cannot see well are said to have defects in their vision. </li></ul><ul><li>The common defects of vision are: </li></ul><ul><li>shortsightedness , </li></ul><ul><li>long-sightedness , </li></ul><ul><li>astigmatism , </li></ul><ul><li>colour-blindness and </li></ul><ul><li>presbyopia </li></ul>
What do you see? Do you know what MYOPIA is?! 1.7 Light & Sight
1.7 Light & Sight Shortsightedness (myopia) Able to see near objects clearly but cannot see distant object. To correct this defect, the person has to wear concave lenses .
SHORT SIGHTEDNESS NORMAL VISSION SHORT SIGHTEDNESS 1.7 Light & Sight
1.7 Light & Sight A distance object cannot be seen clearly because the image is focused in front of the retina. This is because the eye lens is too thick or the eyeball is too long. It is corrected by using a concave lens to diverge the rays of light on the retina.
NORMAL VISSION LONG SIGHTEDNESS Do you see the difference? Is this what we call HYPEROPIA?! 1.7 Light & Sight
1.7 Light & Sight Longsightedness (Hypermetropia) A longsightedness person can see distant objects clearly but cannot see near object. To correct this defect, the person has to wear convex lenses .
1.7 Light & Sight A near object cannot be seen clearly because the image is focused behind of the retina. This is because the eye lens is too thin or the eyeball is too short. It is corrected by using a convex lens to converge the rays of light on the retina.
1.7 Light & Sight Astigmatism Astigmatism is a common vision defect caused by the irregular surface of the cornea. Things look blur to a person with astigmatism. This defect of vision can be corrected using cylindrical lenses.
1.7 Light & Sight Now test your eyes for astigmatism by looking at the figure below. If one or more lines in the chart appears clearer and black but the others appear blurred, then you have astigmatism. astigmatism image normal image
1.7 Light & Sight Can you see the craters on the moon ? Can you see microorganism in the air?
1.7 Light & Sight Limitation of Sight Our sense or sight has its limitations. We cannot see objects that are very tiny, such as bacteria, viruses and atoms with our naked eye. We also cannot see the stars and planets that are very far from Earth. Examples of limitations of sight are: (a) optical illusions (b) blind-spot
1.7 Light & Sight Optical illusions The image formed in the eye is accurate but the brains plays a trick and makes the image misleading.
1.7 Light & Sight Blind-spot (scotoma) The blind spot is the point on the retina where the optical nerve leaves the eye. Close your left eye and stare at the cross mark in the diagram with your right eye. Now slowly move toward the diagram. Keep looking at the cross mark while you move. At a particular distance, the spot will disappear (it will reappear again if you move even closer). The spot disappears because it falls on the optic nerve head, the hole in the photoreceptor sheet.
1.7 Light & Sight Stereoscopic and monocular vision Stereoscopic vision Monocular vision Location of the eye Differences Size of the field of vision Overlapping field of vision Importance of vision Examples At the front of the head Small Large area of overlapping fields <ul><li>Can estimate distance </li></ul><ul><li>accurately </li></ul><ul><li>see things in three </li></ul><ul><li>dimensions </li></ul>Tigers, owl, human beings One on each side of the head Very large Small area or no overlapping area <ul><li>Can see predators in all </li></ul><ul><li>directions </li></ul><ul><li>cannot judge distance </li></ul><ul><li>accurately </li></ul>Pigeons, rabbits, cows, fish
1.7 Light & Sight Devices to Overcome the Limitations of Sight Optical instruments Used to study small objects and specimens mounted on slides Used to study stars in the sky Used to observe distant objects Used by submarine to look out above the surface of the sea Used to scan and see the fetus of a pregnant mother
1.9 Stimuli & Responses in Plants Respond in plants to stimulus is known as tropism . <ul><li>Phototropism </li></ul><ul><li>Def.: Respond of plant to light </li></ul><ul><li>+ve phototropism Shoots grow towards light </li></ul><ul><li>-ve phototropism Roots grow away from light </li></ul><ul><li>+ve phototropism helps green plants to make food by photosynthesis </li></ul>
1.9 Stimuli & Responses in Plants <ul><li>Hydrotropism </li></ul><ul><li>Respond to water by plants </li></ul><ul><li>+ve hydrotropism Roots grow towards water </li></ul><ul><li>-ve hydrotropism Shoots grow away from water </li></ul><ul><li>+ve hydrotropism helps the roots to get water </li></ul><ul><li>Roots are attracted more by water than by gravity. </li></ul>
1.9 Stimuli & Responses in Plants <ul><li>Geotropism </li></ul><ul><li>Respond to gravity by plants </li></ul><ul><li>-ve geotropism Shoots grow upwards against gravity </li></ul><ul><li>+ve geotropism Roots grow downwards towards gravity </li></ul><ul><li>+ve geotropism helps the roots to get water and to anchor the plants firmly into the soil for support </li></ul>
1.9 Stimuli & Responses in Plants <ul><li>Thigmotropism </li></ul><ul><li>Some plants with soft stems climb up a support when they touch it </li></ul><ul><li>They climb by twining, by using tendrils or thorn/hooks </li></ul><ul><li>This respond to touch by plants is called thigmotropism </li></ul><ul><li>Thigmotropism helps plants to get sunlight for photosynthesis </li></ul>
1.9 Stimuli & Responses in Plants <ul><li>Nastic movements </li></ul><ul><li>A movement made by plants in response to stimuli that may come in any direction </li></ul><ul><li>The leaves of the mimosa plant close up when they are touched </li></ul><ul><li>A nastic movement response helps to protect the plant from injury </li></ul>