6 The degree of sensitivity of the skin depends on the: 1.Thickness of the epidermisThe thinner the epidermis, the more sensitive the skin is to the stimulus2. Number of receptors present PMR 05The more receptors found on the skin the more sensitive is that part of the skin.
7 Other functions of the human skin. Water proofprevent water loss from skin.Prevents entry of microorganisms that cause illnesses.Remove waste productsexcess water, urea and mineral salts.Produces Vitamin D in the presence of the sunlight.Stabilise body temperature
8 Fill in the blank with the suitable terms given in the box. Receptors thickness thinner sense of touch touch more number The skin is an organ of __________________There are five types of __ ___ in the skin sensitive to various stimuli.The sensitivity of the skin depends on the ___________ of the epidermis and the ____________ receptors on the skin.The ____________ the epidermis, the more sensitive it is to stimulus.The ________ receptors there are on the skin, the more sensitive it is to stimulus.Blind people use their ____ to help them read Braille
14 Sense of smellWhen we have a cold or flu, a lot of mucus is produce. The smell receptors are surrounded by this thick layer of mucus and vary little of chemical vapor gets to the smell receptors. Therefore, the smell receptors do not get stimulated enough to effectively function as a sensory organ of smell.
15 The sensitivity of the nose towards stimuli is influenced by the following factors: PMR 05 The strength of the smell. A stronger smell will be detected by the nose easily compared with a weaker smell.The presence of mucus in the nose. A lot of mucus will reduce the sensitivity of the nose.
16 Human ear A human ear has three main part. the outer ear, filled with air.The middle ear, filled with air.The inner ear, filled with liquid
24 FUNCTIONS OF DIFFERENT PARTS OF THE HUMAN EAR OUTER EARPinnacollects and directs sound waves into the ear canal.ear canal / auditory canaltransmits sound waves to the eardrum.Eardrumvibrates and transmits sound waves to the ossicles.MIDDLE EAROssiclesintensify the vibrations of the sound waves by 22 times before transmitting to the oval window.Eustachian tubebalances the air pressure at both side of the eardrum.oval windowtransmits sound vibrations from the middle ear to the inner ear.INNER EARCochleatransforms sound vibrations into impulses.semicircular canalsbalance the body position.auditory nervessend messages to the brain which interprets the messages as sound.
25 Stereophonic hearing Stereophonic hearing is hearing using both ears. The advantages of stereophonic hearing:enables the direction of the source of hearing to be detected more accurately.This is because the ear nearer the source of sound receives sound louder and earlier than the other ear.Animals that have stereophonic sound can detect the presence of preys and predators more quickly.
26 Properties of sound sound can transferred through; solids liquids gasescannot be transferred through in vacuum.(particles in solids and liquids are closer each other compared to the molecules in gases. Vacuum is space that does not have any particles.)
27 ANIMAL Frekuansi snake 100-800Hz frog 50-10 000Hz dog 10-50 000Hz cat The range of frequencies of hearing in man is 20 Hz until Hz. The following table shows the range of frequencies of hearing of several animals:Different people have different limitations of hearing.ANIMALFrekuansisnakeHzfrogHzdogHzcatHzbatHzgrasshopperHzwhale10-50HzHuman20hz – hz
29 Reflection and absorption of sound Sound can be reflected or absorbed by the surface of an object.The sound reflected repeatedly from one surface is known as echo.Surfaces that are smooth, even and hard are good sound reflectors and produce loud echo. For examples, concrete, plank, metal and mirrorSurfaces that are rough, hollow and soft are good sound absorbers and produce weak echo. For examples cloth, sponge, cork, rubber, carpet and cushion.
30 To overcome the limitations of hearing, we use the stethoscopeenables doctor to detect the soft heartbeats of patients.ii. hearing aidscollects sound signals before being sent to the middle ear.iii. amplifierboosts weak sound signals.
39 FUNCTIONS OF DIFFERENT PARTS OF THE HUMAN EYE Structure / characteristicFunctionScleraMaintains the shape of the eyeballProtects the eyeballcornearybbChoroidsConjunctivairispupilLens PMR 04Transparent and elastic convex lensRefracts and focuses light onto the retina.ciliary musclesupportive ligamentvitreous humouraqueous humourRetina PMR 2011optic nerve
48 Mechanism of Sight PMR 03, 07 ii. focusing distant object. The eye lens focuses the image onto the retina by changing the thickness of the eye lens. The thickness of the lens is changed by the cilliarry muscles.i.Focusing near objectsTo focus near objects onto the retina, the cilliarry muscles contract. The eye lens become thicker.ii. focusing distant object.To focus distant objects onto the retina, the cilliarry muscles relax. The eye lens becomes thinner.
70 Experiment short sightedness & long sightedness InstructionsFirst, I want you to form groups of four. In your group, discuss why some people wear glassesNext, I want you to look at the first picture on the screenClick and drag the picture from left to right. Observe what happens to the imageThen, repeat the activity on the second and third pictures
71 QuestionsWhy do some people wear glasses?What is the cause of short sightedness?Where does the image fall when a short sighted person look at a far object?What kind of lens is used to correct short sightedness?
72 Formative Assessment Types of Defects Able to see close/near objects (clear/blur)Able to see distant object (clear/blur)Types of lens used to correct defects1) Short sightedness2) Long sightedness3) Astigmatism
73 Complete the diagram Short sightedness Long sightedness The image falls _______ of the retinaThe image falls ______of the retina
80 Blind spotThe blind spot is a spot on the retina of the eye that cannot detect light stimulus.The image of the object formed at the blind spot cannot be seen by the eye because there are no light-sensitive cells (photoreceptors) at the blind spot.