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Sense and Control Year 9 Science Sight Eyes provide what many would regard as the most important of all our senses—sight. The eye contains several parts similar to a camera. Both perform similar tasks—focusing on and capturing images. Eyes and Cameras The Eye Eye Protection Eyebrows and eyelashes help keep dust out. Tear ducts produce tears to flush out any foreign particles. Eyes are set back in depressions in our skulls called orbits to give them some protection from being knocked. Protective eyewear should always be used in science classes when handling or heating chemicals that could spit or spill from their containers. Eye Protection Protective eyewear should always be used in science classes when handling or heating chemicals that could spit or spill from their containers. If a foreign substance does get into your eye, flush it immediately with water while trying to keep your eye open to allow water to contact the affected area. An eyewash bottle should be available for this purpose. Why two eyes? Two eyes allow us to judge distance more accurately. Each eye sees a slightly different view and the brain combines the two images to create a 3D view. This is known as binocular vision. Colour vision The retina contains specialised cells called rods and cones. Rods are more sensitive and only respond to light and dark. Cones need more light to be active and come in three types; red, blue and green. A scanning electron microscope photograph of rods and cones Colour Blindness People who lack one or more types of cones cannot tell the difference between colours, or are colour blind. 1 in 15 males is colour blind 1 in 1000 females is colour blind Ishihara Test for Colour Blindness Ishihara Test for Colour Blindness The individual with normal colour vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) colour blindness will see a 2 revealed in the dots. Animal Eyes The eyes of different animals are highly specialised. rabbit’s eyes are positioned on the sides of its head so that it can see most of its surroundings without moving its head and attracting attention. The eagle has excellent eyesight and can detect a rabbit from three kilometres away Animal Eyes Owls have both eyes at the front to allow better judgement of distance when swooping on prey. Insects may have multiple lenses to provide an all-round view. Spiders have four, six or eight eyes, and scorpions have between six and twelve. Eye Defects In some people the lens has become less elastic and is unable to focus images at exactly the right position in the eye. Myopia (short-sighted) Hyperopia (long-sighted) Presbyopia – a person looses the ability to focus at short distances due to age. Eye Defects Hearing Parts of the human ear Hearing Sound Waves The human ear can detect sound waves. The sound waves cause small but rapid pressure changes to anything they strike. The ear turns these pressure changes into electrical impulses, which are then sent by nerves to the brain for interpretation. The Ear Describe the structure and function of the following parts of the ear and Indicate the section of the ear that each part fits into. Eardrum Hammer, anvil and stirrup. Oval window Cochlea Auditory nerves Semicircular canals Two Ears Two Ears Two ears help us determine the direction of a sound. If a sound reaches both ears at the same time, our brain tells us that the source of the sound is directly in front of, behind or above us. If a sound reaches the left ear before the right ear, the brain tells us that the source of the sound is to our left. Why do we have two ears? Think of some of the adaptations some animals have with their different ear shapes and sizes. Ear Problems Prolonged exposure to loud sounds can flatten the hairs of the cochlea. As the hairs recover so does your hearing, but not completely. Deafness can be cause by a build up of wax, jamming of the ossicles together, birth defects, noise and infections Hearing Problems Explain the cause and effects of flattening of the hairs of the cochlea. Explain the cause and effects of a rip to the eardrum. Ear Protection List ways to minimise hearing problems. Hearing Technologies. Hearing aids work to amplify sounds and transmitting them to the auditory canal. Hearing Technologies. Cochlea implants replace the inner ear. A microphone sends information to a speech processor which sorts out information and sends it to a receiver that stimulates the cochlea. Messages are then sent to the brain. Touch The skin is an organ containing millions of nerve endings that transmit information about touch, pain and temperature to the brain. The Skin The skin is bodies protective outer boundary. It is the largest organ of your body. It has many functions including: Protecting the body from germs Helps control your body temperature Stops you from dehydrating Forms vitamin D in sunlight Releases water and other waste Detects pain, pressure, heat and movement. Skin Conditions A wart is a raised rough, dry lump on the surface of the skin. A mole is a raised dark coloured growth of the skin. Freckles are dark spots of melanin. Pimples are caused when the sebaceous gland secretes to much or into a hair follicle or the follicle is blocked. Skin Cancers Basal cell carcinomas – usually are red flaky lumps on the skin. Squamous cell carcinomas – red scaly sores that spread. Melanomas – the most deadly skin cancer that spreads rapidly. Where is the skin most sensitive? Method 1 Attach two toothpicks to a ruler as shown. 2 Make sure your partner cannot see while you touch both toothpick points to a region of skin. Ask your partner how many points they feel. 3 Move the toothpicks closer to each other and test again. Progressively move the toothpicks closer together until only one can be felt. 4 Test other regions of the skin the same way. Some possible areas to try are the back of the hand, palm, inside forearm, back of forearm, leg, foot, back of neck. 5 Swap jobs and have your partner test you. Where is the skin most sensitive? Where is the skin most sensitive? Distance between two points in mm. Part of the skin Your partner You Palm Knee Cheek Forehead Back of hand Sense of smell Smell Smell is detected when tiny particles enter the nose and dissolve in its moist lining. The dissolved substances trigger olfactory nerves, which send messages to the brain. Smell fatigue Aim To investigate the phenomenon of smell fatigue. Equipment A safe, strong-smelling substance, a watch, a small container. Smell Fatigue Method 1 Obtain a sample of a safe, strong-smelling substance in a container that can be sealed. 2 Carefully take a small whiff of the substance. Do not breathe in too deeply. 3 Re-seal the container and wait 30 seconds before taking a similar whiff. Rate the strength of the smell from 0 (no smell) to 5 (the strength of your first smell). 4 Continue to take a whiff every 30 seconds, giving the strength of the smell a rating each time until you have about six ratings. Smell fatigue Describe what happens to the strength of what you smell after several whiffs. Construct a graph to display your ratings. Taste The tongue is covered bumps, called papillae. The taste buds are embedded between the papillae. Humans can detect five taste sensations: sweet, sour, salty, bitter and umami (savoury). Taste Bud Taste Saliva in our mouths dissolves samples of food so taste buds can detect taste and send messages to the brain. Flavour When we eat, our senses of smell and taste work together to detect flavour. As much as 80% of what we perceive as flavour is actually smell. Flavour is largely the smell of gases emitted from food that has just been taken out of your mouth. Brand name versus no name Aim To compare the taste of various products and investigate the role of smell in the taste process Equipment Samples of various edible substances; blindfold; new plastic cups ‘brand name’ chocolate, ‘no name’ chocolate, brand name lemonade, ‘no name’ lemonade, brand name biscuits, ‘no name’ biscuits Brand name versus no name Method 1 Work with a partner or group and blindfold one person. 2 Give the blindfolded person a taste of a ‘brand name’ and ‘no name’ pair of foods, and record their observations. 3 Repeat for the other food items. 4 Repeat the tests, but have the tester pinch his or her nose shut while tasting. Responding Through our senses we constantly receive information. Responding to this information allows us to react, enhancing our chances of survival. Sense Receptors Stimulus Location of receptor Heat or cold Thermoreceptors in the skin Water levels in the blood Osmoreceptors in the brain and arteries Pressure and touch Mechanoreceptors in the skin Sound Cochlear cells in inner ear Light Photoreceptors in retina of eye Chemicals Chemoreceptors on the tongue and nose Gravity Semi circular canals in the ears Stimulus-Response Model A stimulus is something acting on an receptor that causes a change in the organism. A message is then sent to a effector, which is anything that causes a response (eg a gland or muscle). Feedback Information on the stimulus-response so the organism can adjust any further responses. Coordination The total response of an organism to stimulus, possibly involving several parts of the body. The Nervous System The nervous system has two parts: • the central nervous system • the peripheral nervous system. The central nervous system (CNS) is made up of the brain and spinal cord. They act as a control centre, receiving messages from all parts of the body, examining the data received, and then sending out messages to tell parts of the body what to do. The Nervous System The peripheral nervous system (PNS) is made up of sensory receptors and nerves. These continuously inform the CNS of changing conditions, and transmit the decisions made by the CNS back to effector organs. Messages are passed through the system by nerve cells called neurons. Neurons Specialised cells that transmits and receives messages in the form of electrical impulses. Sensory Neurons Sensory neurons, have specialised endings sensitive only to stimuli such as heat and light. These form part of the body’s larger sense organs (eyes, ears etc.), which function by collecting different energy forms. The sensory neuron then converts this energy into an electrical impulse. Other Neurons The connecting neurons or interneurons, transfer these electrical messages within the CNS. A third type, motor neurons, transfer messages from the CNS to effector organs such as muscles. The Nervous System Use page 241 of your textbook to answer these questions. 1. What is the CNS? 2. What is the PNS? 3. What are neurons? 4. Name the three types of neurons and describe their functions. Synapse There are small gaps between the neurons known as synapses. Messages move across the gap by chemical compounds called neurotransmitters. Drugs like cocaine and ecstasy increase the production of neurotransmitters resulting in a heightened state of alert. Synapse Reflex arc A stimulus is detected by the receptors and is sent along a sensory neuron to the spinal cord. The message then is carried by a motor nerve to the effector, without involving the brain. Reflex Arc The Endocrine System Chemical Control Hormones The endocrine system uses chemical messages called hormones to transfer information around the body. These hormones are responsible for controlling many changes that occur in our bodies such as growth, reproduction water balance and the rate of chemical reactions in cells. Hormones Hormones travel to all parts of the body but only cells targeted respond to the hormone. A hormone has a specific shape that fits chemically on the targeted cells membrane. Why hormones? The circulation of hormones takes time but once the hormone has reached the cell the effects are long lasting Control of blood glucose levels The Brain The brain is made up of around 25,000 billion neurons which are connected to as many as 1000 others. This huge number of neurons form specific circuits Structure of the brain The brain is made up of three main parts. The cerebellum controls complex muscular movements like cycling walking and running. The medulla controls vital involuntary functions like heartbeat and breathing. The cerebrum makes up 90% of the brains volume and is divided into the left and right hemispheres. The Human Brain Right Hemisphere Characteristics Intuitive •Responds to demonstrated instructions •Problem solves with hunches, looking for patterns and configurations •Looks at similarities •Is fluid and spontaneous •Prefers elusive, uncertain information •Prefers drawing and manipulating objects •Prefers open ended questions •Free with feelings •Prefers collegial authority structures Simultaneous •Is a lumper: connectedness important •Is analogic, sees correspondences, resemblances Draws on unbounded qualitative patterns that are not organized into sequences, but that cluster around images Left brain characteristics Rational •Responds to verbal instructions •Problem solves by logically and sequentially looking at the parts of things •Looks at differences •Is planned and structured •Prefers established, certain information •Prefers talking and writing •Prefers multiple choice tests •Controls feelings •Prefers ranked authority structures Sequential •Is a splitter: distinction important •Is logical, sees cause and effect Draws on previously accumulated, organized information The Pituitary Gland The pituitary gland plays an important role in controlling growth. It not only releases hormones but also instructs other cells to release their hormones. The gland receives instructions from the hypothalamus in the brain linking the endocrine and nervous systems. Dissection Rules Stay safe Follow all directions Always cut away from yourself and others. Leave the brain on the tray at all times Clean up when instructed