Unit 5 Nervous System And The Senses

Science Interactive LTD Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk Science Interactive LTD Copyright 2005 Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150 PowerPoint slides . Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images , graphics , challenging exercises and questions . Units can be used in the classroom via an interactive whiteboard , data projector or used during individual study via a PC or school network . Unit 19: The Transitional Metals Unit 18: Metals and their Properties Unit 17: The Alkali Metals Unit 16: The Periodic Table and its Elements Unit 15: Genetic Engineering Unit 14: Evolution and Human Impact Unit 13: Inheritance and Selection Unit 12: Mitosis and Meiosis Unit 11: Flow of Energy and Elements through the Environment Unit 10: Water Transport in Plants Unit 9: Photosynthesis in Green Plants Unit 8: Drugs and Bad Body Maintenance Unit 7: Hormones and the Endocrine System Unit 6: Human Homeostasis Unit 5: Nervous System and the Senses Unit 4: The Respiratory System Unit 3: Healthy Body and Immunity Unit 2: The Circulatory System Unit 1: The Digestive System Unit 38: Cells, Tissue, Organs and Organs systems Unit 37: Natural Forces Unit 36: Sound and Hearing Unit 35: The Alkaline Earth Metals Unit 34: The Earth and Plate Tectonics Unit 33: Earth and Space Unit 32: Newton's Forces and the Effects of Forces Unit 31: Radioactivity Unit 30: Light and the Electromagnetic Spectrum Unit 29: Electricity Unit 28: Generating Electricity and its Domestic Use Unit 27: Energy Unit 26: Rates of Reaction Unit 25: The Noble Gases, their Properties and Uses Unit 24: The Halogens, their Uses and Compounds Unit 23: Ionic and Covalent Compounds Unit 22: Elements, Molecules and Compounds Unit 21: Rock Cycle Unit 20: Crude Oil and its Products

Unit 5

Nervous System and Senses

The role of the nervous system and its key organs.

The roles of the parasympathetic and sympathetic nervous system.

The role of the receptors, effectors, sensory and motor neurones.

The nature of the synapse and its neurotransmitters.

How drugs affect the nervous system.

The role of human reflexes and the reflex arc as a protective mechanism against injury.

The role of human senses.

The function of the human eye.

The function of the human ear.

The role of other types of senses and receptors of the nervous system.

Nervous, System, Neurone, Sympathetic, Parasympathetic, Reflex arc, Sensory, Motor, Sight, Hearing, Taste, Touch, Smell, Relay, Receptor, Effector, Senses, Synapse, Electrical, Chemical & Neurotransmitter. Unit 5: Nervous System and the Senses web: www.science-interactive.co.uk email: sales@science-interactive.co.uk Science Interactive LTD PO BOX 50764 LONDON NW6 9AT Click mouse to begin Science Interactive LTD Copyright 2005 Understand: Keywords:

The Nervous System The nervous system controls and coordinates all your basic voluntary and involuntary actions. It also enables us to enjoy all those human qualities or emotions like self awareness, empathy, speech, intelligence, memory, humour and love. The main parts of the nervous system include your b_______, spinal column, peripheral nerves and sense organs, for example the eyes and ears. The main building block of the nervous system is the neuron or nerve cell. What is the other system which controls your body's actions ? Parts of the nervous system: Science Interactive LTD Copyright 2005 Word bank: brain The peripheral nerves connects the very far extremities of the body to the brain through a network of neurons. Relays information like sound, touch and smell. Peripheral nerves Humans have five main senses. Our senses inform us of events that happen around us. Our senses detect stimuli like sound, temperature, touch, smell and light. Senses Conveys all nerves to and from the brain. The spinal cord or vertebrate contains many thousands of nerves in a protective bone channel. The brain coordinates the entire nervous system. It controls all the voluntary and involuntary actions as well as intelligence speech and memory. Notes Diagram Human brain Spinal cord

Coordination of the body one The central nervous system, comprising of the b______ and spinal cord is connected to a vast network of effectors (muscles and glands) and sensors (colour, taste temperature and sound) by nerves cells called neurons . Your brain coordinates all basic information provided by sensors located around the body and intrinsic thoughts formed in the brain and determines an appropriate response. Therefore it is able to make sense of all the thousands of bits of data that it continuously creates or receives and processes. Why is the brain compared to the CPU of a computer ? Organisation of the nervous system: Science Interactive LTD Copyright 2005 Word bank: brain The spinal cord contains many nerves that carry information to and from your brain. Sever your spinal are you will be paralysed for life. Spinal cord Effectors like muscles in the arm respond to nerve impulses. These can also be glands which release hormones like adrenalin and thyroxine into the bloodstream. The brain coordinates your actions and is responsible for your memory, intelligence and speech. It weighs over 2 kilograms in the average adult. Sensors respond to information like light, colour, sound and touch and send electrical messages to the brain. These messages reach the brain via the spinal cord. Notes Diagram Sensors Brain Effectors

Coordination of the body two All involuntary actions that support life ( i.e. heart rate, blood pressure & hormone levels ) are coordinated by your n_________ system. This coordination can be divided into two different parts: Parasympathetic and sympathetic parts of your nervous system. One responds (sympathetic), the other calms (parasympathetic) Answer these questions using this diagram. The nervous system: Science Interactive LTD Copyright 2005 Word bank: nervous Questions on the nervous system. Sympathetic Parasympathetic What part of the nervous system takes control of the body when you become aggressive ? What part of the nervous system does heroin affect the most ? What part of the nervous system does alcohol affect the most ? If there is no pupil reflex after a traffic injury what does this tell you about the brain ? Which part of the nervous system do anti-blood pressure drugs treat ?. During an asthma attack which part of your nervous system is responsible for constricting your airways ? When you are asleep which system almost causes organ shut down ? When you are meditating, which system will you try and control ? Which part of the system causes increases in your heart rate ? Which part of the nervous system is in use after eating a meal ?

The voluntary part of your nervous system is controlled by you. Your brain takes a decision and the nervous system forwards the appropriate m________ or impulses to the right muscle groups. When you get an itch on your scalp, for example, a chain of events follows, leading to you scratching the itch. All this information is collected, sent and processed by your n________ system. How is this response different to the blink reflex that protects your eye from dust or dirt ? Voluntary part of the nervous system: Coordination of the body three Science Interactive LTD Copyright 2005 Word bank: message nervous Effector Coordinator Response Receptors located in your skin detect an itch on your scalp. This begins the process. You have many other types of receptors in your skin. The receptor cells send an electrical message along a sensory neurone through the spinal cord to your brain. The brain receives the message that you have an itch and decides on the right response. The message is sent to your muscles in your arm, elbow and hand from the brain by motor neurones. It tells your elbow and hand to scratch the itch The response in this case is to relieve the itch or irritation and scratch the itchy scalp. The cycle is complete. Notes Diagram Stimulus Receptor

Producing the right response The reactions coordinated by the nervous system, all occur in a similar way. A chain of events begins with s________, which are detected by receptors, coordinated by the nervous system, with effectors like muscles producing the response. Imagine if you trod on a broken piece of glass. What is the stimulus, How is this detected by receptors in your skin, What is the effector producing which response ? Stimulus Receptor Coordination Effector Response: Science Interactive LTD Copyright 2005 Word bank: stimuli Effector Coordinator Response A stimulus can include a bright light, touch, hot or cold or a sound. These stimuli are detected by our senses. Receptors found in our senses and our skin are specialised and highly adapted to respond to the external stimuli. The peripheral nerves and the central nervous system function together to coordinate and respond to stimuli. An effector, like a muscle will contract when a nerve message is sent to produce the correct response. The response in this case prevents further injury from the sharp object. You respond even without thinking ! Notes Diagram Stimulus Receptor

Human senses Our senses inform us of events that happen around us. Our senses detect different types of stimuli and we respond. Humans have five main s_______. These are smell, touch, taste, hearing and v______. Our brain is able to coordinate all the information our senses collect and make appropriate responses automatically. Interestingly, accommodating vision alone takes large amounts of the brain’s capacity. This is considered as the most important human sense. Imagine you were blind, how would your other senses compensate ? Human senses: Science Interactive LTD Copyright 2005 Word bank: senses vision Our ears responds to sound or vibrations, giving us a sense of the pitch and loudness of a sound. How do ears collect sound ? Hearing The nose responds to chemicals in the air that we breathe. Our sense of smell is most associated with memory. Smell Our skin can respond to a number of stimuli including touch and pressure. Where is the skin most sensitive ? Touch Your tongue responds to taste chemicals in our food, for example, bitter, sweet, salt and sour. Why is taste a protective sense ? Your eyes respond to light rays and colour giving us a picture of our surroundings. It is the most important sense that we have. Vision Taste

The nerve cell The main building block of the nervous system is the neuron or nerve cell. Nerve cells are very different from other cells. Although they do have a cell membrane, n_______ and cytoplasm like other cells, their shape reflects their communicating function. Part of the cell is stretched to form the axon which can be over one metre long . They carry information using electrical signals. The nerve cell: Science Interactive LTD Copyright 2005 Word bank: nucleus The messages that are carried by the neurons are called nerve impulses. These are electrical signals. They travel at relatively high speeds along the axon of the nerve cell. An impulse can be repeated if the stimulus repeats. They travel along the same nerve, one after another. In multiple sclerosis, the insulating fatty sheath breaks down and the electrical impulses slow or even stop. People with this disease loose the use of their muscles, even those you use to breathe over a relatively short time period. This disease is fatal for all those individuals diagnosed. How nerve messages are carried Nerve cells are very different from other cells. Their shape reflects their function. Part of the cell is stretched to form the axon which carries electrical signals. Nervous tissue forms a complex number of pathways allowing communication from sensors to the brain and effectors like muscles and endocrine glands. Notes Diagram Nerve cell and tissue

Motor and sensory neurons There are two types of neurone that are found in the nervous system: Organisation of the nervous system: Sensory neurone: Carries messages from receptors to brain. Motor neurone: Carries messages from brain to effectors. Science Interactive LTD Copyright 2005 Axon Dendron Cell Myelin Nerve impulse Sense body Dendrites Nucleus sheath Myelin fibres Axon body sheath receptor Nerve impulse Cell Muscle Axon Dendron Cell Myelin Nerve impulse Sense body Dendrites Nucleus sheath Myelin fibres Axon body sheath receptor Nerve impulse Cell Muscle Motor neurones carry information from the brain via the spinal cord. They convey information to effectors that produce a response like moving a muscle or releasing a hormone. Their cell body is located in the central nervous system. Sensory neurones carry information to the brain via the spinal cord. They convey information from touch, temperature or pain rectors embedded in the skin. Their nerve endings (dendrites) are located in the central nervous system. Notes Diagram Sensory neuron Motor neuron

The synapse The brain contains millions of neurones forming a vast and complicated network of neural pathways. Where the end of one neurone connects to another, there is a small gap called a synapse . When an impulse reaches the end of an axon, a chemical is produced. This chemical is called a neurotransmitter . It d_________ across the gap and starts an e________ impulse in the next neurone. How a synapse works: Science Interactive LTD Copyright 2005 Word bank: diffuses electrical The chemical neurotransmitter is manufactured at the terminal axon and is released into the synaptic gap. It then begins to diffuse across the gap to the next neurone or effector like a muscle or gland. It takes about one hundredth of a second to diffuse across the membrane. When the neurotransmitter lands on the next neuron or effector, it triggers the next impulse or a response. How do stimulants and depressants affect our synapses ? Notes Diagram The synapse The synapse up close

The synapse There are many millions of synapses in the brain that carry on the impulses between neurones. Our s___________ are affected by drugs (stimulants and depressants) like painkillers, cocaine or alcohol. Painkillers like paracetamol or aspirin block pain, by stopping the release of chemical neurotransmitters. Drugs like cocaine can i_________ the amount of neurotransmitter between the synapses giving the users a ‘drug high.’ How do depressants like alcohol affect our synapses ? Drugs affecting synapses: Science Interactive LTD Copyright 2005 Word bank: synapses increase Painkillers like aspirin or paracetamol act to block or reduce the amount of neurotransmitter released in the synapse therefore stopping the pain pathway. Name three types of pain killers ? Depressants Hallucinogens like LSD affect the brain and a persons perception in many ways. LSD causes a massive over stimulation of your synapses causing the main known effects; seeing hallucinogenic images. Hallucinogens Stimulants increase the amount of synaptic neuro-transmitter. This increases their intended effects on the body giving the users a drug high. Stimulants include nicotine, caffeine and amphetamines. There are billions of synapses in the brain connecting billions of different nerve cells. Certain drugs like stimulants can affect how the nerve synapse works and functions. Notes Diagram Synapses as junctions Stimulants

The reflex arc one You have many reflexes that are able to protect you from injury or danger. These responses or reflexes occur very quickly and without you t___________. This is because the reflex pathway through the nervous system misses the b_____. A reflex begins with a stimuli like extreme heat and ends in a rapid response like muscle contraction You have three main reflexes: Blink reflex, Cough reflex and Pupil reflex. Reflex arcs in humans: Science Interactive LTD Copyright 2005 Word bank: thinking brain To control the amount of light entering the eye, our pupils varies their size depending on how much light is available. How long does it take you to adjust to light, when you awake from sleep? Pupil reflex The cough reflex protects our airways when food enters our trachea instead of our food pipe. This reflex is essential so that that airways remain free from food. Name a reflex in a newborn not found in adults ? To protect the eye against injury from objects moving towards the delicate eye surface. What would happen if you couldn’t blink and how would this affect the eye ? Function Diagram Blink reflex Coughing reflex

The reflex arc two Reflexes in humans are a protective adaptation that helps us survive and avoid serious injury. A reflex is a rapid response to a stimuli that follows a particular route from stimulus (hot object) to response (moving away your hand.) This pathway is called the reflex arc . How does the blink reflex help protect your delicate eyes ? The reflex arc: Science Interactive LTD Copyright 2005 Word bank: skin spinal effector Response Effector Motor neurone Interneuron Sensory neurone Receptor Stimulus Step Muscle or gland. Muscle movement causes release of the hot object. No further injury is caused to the body. Carries message to the e_______. Carries message through cord. Carries message to s_____ cord. Temperature receptor in s____. Hot object Function (complete table)

Your senses Your surroundings or the environment you are in are always changing. Humans and animals need to respond to environmental stimuli like light, taste, sound, touch and smell. We have different receptors to detect these changes in our environment. Any change is called a s________. These receptors to the stimuli are found in very different parts of our body, for example in our sense organs like the eyes and ears and in our s______. Describe in detail all the different stimuli that the skin responds to ? Human senses: Science Interactive LTD Copyright 2005 Word bank: stimuli skin Skin Ears Nose Tongue Eyes Touch Hearing Smell Taste Sight

Eyesight the eye The eye allows c_________ and light vision so that you can make sense of your environment and your place in it. The eye relies on a number of specialised cells and tissues to focus an image, determine its colour, size, shape and position and send this information to the b______. Why does having two eyes give you better perception of your environment and the distance between objects ? The human eye: Science Interactive LTD Copyright 2005 Word bank: brain retina colour Optic nerve Fovea Retina Vitreous humour Aqueous humour Lens Iris Pupil Cornea Tissue Optic nerve: carries information to the brain. Helps see objects in close detail. Helps keep shape of the eyeball. Contains all rod and cone cells to detect light and c_______. Helps keep shape of lens. Focuses light image onto r________. Controls the amount of light entering the eye. Allows light through the eye. Protects the lens and begins to focus incoming light rays. Function (complete table)

Eyesight forming an image one The human eye is our link to the outside world conveying millions of i________ every year to our brain, that allows us to understand and manipulate our own environment. A large part of the brain is dedicated to understanding the images collected and sent by the eyes. The eye is like a simple c________, with a lens that focuses an image. Both camera and eyes are also able to control the amount of incoming light . The image formed by both the eye and the camera are also the same: It is upside down, smaller and also virtual ! Forming an image: Science Interactive LTD Copyright 2005 Word bank: images camera The camera forms an image which is upside down, smaller than the real object and virtual. This image is captured using photographic film. Camera Eye Picture Diagram The eye forms an image which is upside down, smaller than the real object and virtual. This image is sent to the brain via the optic nerve. Notes

Eyesight forming an image two Although most of the bending of light rays is done by the curved cornea, the lens focuses the object on the eye’s r_______. The shape of the lens is controlled by the ciliary muscles and the suspensory ligaments. Light is first bent by the c________, then by the clear l______. The image is focussed, inverted onto the r______, where the rod and cone cells detect light and colour. These cells convert the image into e___________ impulses which are sent via the o_____ nerve to the brain. The brain interprets this image according to your experiences. It also corrects the image so it is no longer upside down. Forming an image: Science Interactive LTD Copyright 2005 Word bank: retina cornea lens electrical optic The ciliary body contracts when your eye focuses a near object. The lens is therefore allowed to form a fat shape. The ciliary body relaxes when your eye focuses a distant object. The lens is therefore pulled into a thin shape. Ciliary muscle Suspensory ligaments are allowed loose by the contracted ciliary muscles. This allows the lens to form a fat shape so that it can focus a near object like a book. Lens is fat, because rays from near objects need to be bent more to form a sharp image on the surface of the eye’s retina. Near object Distant object Diagram Lens is thin, because the rays from distant objects need to be bent less to form a sharp image on the surface of the eye’s retina. Lens Suspensory ligaments are pulled tight by the relaxed ciliary muscle. This pulls the lens into a thin shape so that the lens can focus a distant object like a stop sign. Suspensory ligaments

Eyesight Correcting sight The image that is formed on the eye’s retina, needs to be sharp and is focussed by the lens. In many people, the lens is unable to form a sharp image. In long sighted people, the lens is too weak and the focal point falls behind the r______. Long sighted people require glasses that use convex lenses. In short sighted people, the lens is too strong, forming an image which is in front of the retina. Short sighted people need to wear glasses with c________ lenses. Do contact lenses work in the same way ? Correcting eyesight: Short sighted Long sighted Concave lens Convex lens Science Interactive LTD Copyright 2005 Word bank: retina concave People wear glasses to correct faults in their eyesight. A pair of glasses help us to produce a focussed image on the eyes retina. Without glasses, life would be much more difficult. Notes Short sighted Diagram 20/20 vision Normal vision Long sighted

Hearing the ear You are surrounded by sound waves, some of them are from background noise and some from words spoken to you by your friends. Your ears work by converting these sound w________ into nerve impulses. Your ear is a collection of tissues that are highly adapted to collect and process these sound waves, so you can make sense of sound. How is the outer and middle ear adapted to collect and funnel waves to the inner part of the ear ? The human ear: Science Interactive LTD Copyright 2005 Word bank: waves sound cochlea transmits T_________ message to the brain. Auditory nerve Contains sensory hair cells which respond to vibrations, sending impulses to the brain. Cochlea Oval window causes the fluid in the c______ to vibrate. Oval window Vibrations are passed through three small bones. Ear bones Ear drum vibrates. Ear drum Funnels sound. Ear canal Collects s_________. Outer ear Function (complete table and draw arrows) Tissue

Hearing detecting sound Each part of the human ear has a specific function in processing sound. The outer ear f_______ the sound waves which then travel to the eardrum. Sound vibrations are then passed to the inner ear drum via three small b______ called the anvil, stirrup and hammer. Sound vibrations are then passed from the inner ear drum to the cochlea. Vibrations then travel down the coiled cochlea causing tiny hair cells to move, triggering nerve impulses to the brain. The higher the pitch, the further down the cochlea the vibrations travel. How does sound over 90 decibels begin to damage hearing over long periods of time. How can we protect our hearing ? The ear in detail: Science Interactive LTD Copyright 2005 Word bank: funnels bones Inner ear Hair sensory cells Outer ear: Shaped like a funnel, the sound waves are collected by the outer ear or pinna and funnelled onto the eardrum. Middle ear: The vibrations from the ear drum vibrates the three little bones located in the middle ear called the anvil, stirrup and hammer. Inner ear: These vibrations are passed onto the inner ear drum, which causes fluid in the cochlea to vibrate The cochlea contains thousands of hair sensor cells which respond to the pitch and loudness of a sound. Sensory hair cells found in the cochlea can be damaged by loud or very high pitched sounds. Your ear also has three semi-circular canals which detect motion and control your balance. Outer ear Middle ear

Smell Your sense of smell or nose is able to sense chemicals in the atmosphere. Your sense of smell is thousands of times more sensitive than your sense of taste. We can detect lots of different smells, from pleasant smells produced by f_________ or perfumes to unpleasant smells produced by rotting foods or sewers. The ‘smell producing chemicals’ that enter your nose, land on its moist surface and stimulates, the millions of tiny sensors that line the nose. These sensors send e________ impulses to the brain which is then able to interpret them. Smell is vital in avoiding off foods or animal waste, exposure to which could make us unwell. During a cold your food tastes really bland, what does this tell you about the role of smell in taste ? Detecting smell: Science Interactive LTD Copyright 2005 Word bank: flowers electrical Perfume The human nose allows us to determine if different foods or substances have a smell. A pleasant smell, for example something rich in sugar or a perfume produces a positive response in humans. Unpleasant smells tells us to avoid those areas or foods. Blue cheese and many other foods that we eat have an unpleasant smell and is an acquired taste. The human nose allows us to smell foods and other objects. Smell is very closely associated with taste. Notes Diagram Nose Blue cheese Off food

Taste Your sense of taste comes from your tongue. Your t_______ is able to sense chemicals in the foods and drinks that you eat. Your taste is many thousands less sensitive than your sense of smell. We can detect four different tastes, sour , salty , b______ and sweet . The ‘taste producing chemicals’ that enter your mouth through eating and drinking, land on the moist tongue surface and stimulate thousands of tiny sensors that line the tongue. These sensors send electrical impulses to the brain which is then able to interpret them. Taste is vital in avoiding off foods, and rewarding us mentally, when we eat sugary foods containing lots of energy. Try mapping out on your tongue where you can detect the four tastes i.e. salt, sweet, sour or bitter ? Detecting taste: Science Interactive LTD Copyright 2005 Word bank: tongue bitter Sour Salt The human tongue can tell four different tastes; Bitter, Salt, Sour and Sweet. This allows us to determine what tastes good and perhaps rich in sugar, making an ideal energy source or to what might tastes off. The bitter taste associated with strong coffee and alcohols like beer is an acquired taste. Children, although they like sour, sweet and salty foods often do not like bitter foods. The human tongue has a number of taste buds located in several areas so that we can taste the different foods. Notes Diagram Tongue Bitter Sweet

Touch and pressure Detecting t_______ and pressure is essential to protect our skin, muscles, joints and bones from serious crippling injuries. During a long film, you may start to feel uncomfortable due to the pressure of sitting on your behind for long periods. Your body will automatically shift your weight, avoiding excess p_________ on your joints and muscles. You do this even when your are asleep, to avoid developing bed sores. Also sensing touch is important to connect us with our environment, the things we move and the people close to us. Try mapping out on the number and location of touch receptors located on your hand. Where do you find the greatest concentration ? Detecting touch and pressure: Temperature Pain Touch Pressure Science Interactive LTD Copyright 2005 Word bank: touch pressure Your skin and other areas of your body can detect the lightest touch or intense pressure. This helps us communicate with other humans in our environment as well as change our body position. Found in the dermal layers of the skin are temperature, pain, touch and pressure sensors which all convey information to your brain. Notes Diagram Human skin Touch Pain

1: Define the following terms: Nervous system, Neurone, Reflex Arc, Senses, Receptor, Effector & Stimuli. 2: Look at the diagram of the three parts of the nervous system. Complete the table. 3: Explain why you should: a) What do we call the changes in the environment to which the nervous system responds. b) What do we call the cells that detect these changes in the environment. c) Suggest some of the advantages of being able to respond and react to changes in the environment. d) How many different types of receptors (e.g. temperature) do you have in your skin. e) Why do you have more touch receptors on the tips on your fingers than any where else on your skin. Extension questions and homework Science Interactive LTD Copyright 2005 Eye Spinal Cord Brain Function of each part in the nervous system Part

4: Match up the sense organs to the following senses: 5: a) Draw and label a general nerve cell. Include features like the cell body, dendrites, axon and myelin sheath. b) What does a sensory neurone and a motor neurone do and are there any differences between the two types of neurones. c) How is the electrical impulse continued from one nerve to the next. d) How do pain killers interact with the nerve impulse to block pain. e) Correct this sentence: A reflex arc is a conscious/automatic response to a stimuli/receptor. It happens very quickly/slowly and involves/does not involve the brain. This protects us from serious injury. 6: Look at the diagram. a) Identify the parts labelled X, Y & Z. b) What is the collective name give to the parts represented by X & Y. c) In which direction can the nerve impulse travel in the part labelled Y. d) Give one function of the part labelled X. 7: a) Give a single function of the following tissues; Lens, Ciliary body, Retina, Optic nerve, Iris, Pupil and Fovea. b) How doe the pupil and the iris work together to control the amount of light entering the eye. c) The lens in our eye is different to a rigid glass lens, it can change shape depending on the distance of the object that it intends to focus. How does it change shape to focus a near and far object. Internet: Go to google.co.uk and find out about spinal injury. Particularly look up and find out about multiple sclerosis, how this disease affects the neurones and electrical impulses. Also find out about spinal injury or paralysis and new research aimed at providing a cure for this injury. X Y Z Science Interactive LTD Copyright 2005 Heart Ear Eye Touch Sound Smell Tongue Pressure Skin Light Nose Chemicals