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The Body In Action A Movement The skeleton The skeleton provides a framework for support and muscle attachment. It also protects important organs such as the brain, lungs, heart and spinal cord. Bones Bones are mad of living cells that form flexible fibres. These cells are supplied with food and oxygen by blood vessels. This is why when you break a bone it will bleed. The fibres are surrounded by hard minerals, mainly calcium phosphate. Bones provide a strong, hard framework for your muscles and body organs. Freshly roasted chicken bones lose their flexibility because the living, flexible part has been destroyed. Acid soaked chicken bones become very pliable and lose their firmness because the acid has dissolved all the minerals from the bone. Joints Where bones of the skeleton meet, joints are formed. Joints allow the skeleton to bend and move in different ways. A typical Hinge joint A typical ball and socket joint Type of joint Examples Ball and socket Hip, shoulder Hinge joint Knee, elbow Type of movement Allows movement in different planes Allows moment in one plane only The structure of a joint At a joint, the bones are held together by ligaments. The joint allows smooth movement. Part of the joint Function Ligament Hold bones together Synovial membrane Makes and releases synovial fluid Synovial fluid Lubricates the ends of the bones , ensuring frictionless movement Cartilage Cushions the ends of the bones; acts as a shock absorber The human arm Muscles are attached to bones by tendons. When a muscle contracts (gets shorter), the tendon pulls on the bones and the arm moves. Tendons are inelastic ie they do not stretch very much so that the movement of the muscle will be passed on to the bone. Muscles can only contract and relax. Therefore most muscles work against each other in pairs. If one muscle straightens the arm, the other muscle bends it. Straight arm Bent arm Biceps muscle relaxed Biceps muscle contracted Triceps muscle contracted Triceps muscle relaxed B The need for Energy Energy needs The amount of energy needed by a person will vary according to their age, gender and lifestyle. If you take in more energy than you use in activity, your body will store fat. If you take in less energy in food than you require for activity, your body will lose fat. Breathing You need oxygen to release the energy from your food. In order to do this, a waste gas, carbon dioxide, is produced. You obtain oxygen and get rid of carbon dioxide by breathing. Your lungs are the organs that allow you to do this. Lung Structure The lungs are spongy organs that have a very large surface area. They feel spongy and will float in water because they have air in them. They are pinky red in colour because they have a good blood supply. Cartilage rings are found around the trachea and bronchi to prevent them from collapsing. The lining of air passages Air contains dust and germs that damage your lungs. The air you breathe is cleaned by cells lining the air tubes. These cells have tiny hairs or cilia that move in waves up to the mouth. A slippery liquid called mucus is made by the cells and this traps dirt. The mucus acts like a conveyor belt that is moved by the beating cilia. In this way dirt and germs are moved up to the mouth where they are swallowed. Gas exchange in the air sacs The bronchi divide into smaller and smaller tubes called bronchioles. Each bronchiole ends in an air sac that is lined in moisture. Oxygen dissolves in this moisture and diffuses from the lungs into the blood because there is a higher concentration in the sir sac than in the blood. Carbon dioxide diffuses in the opposite direction because there is a higher concentration in the blood than in the air sac. Why lungs are efficient gas exchange structures 1. They air sac are thin walled to let gases through easily. 2. The air sacs have many blood capillaries in close contact with them. 3. Because there are so many air sacs, they make a very large surface area. 4. The air sacs are lined with mucus that is moist so that the gases can dissolve. Breathing movements Movements of the chest help us to inhale (take in air) and exhale (give out air). The diaphragm and the intercostal muscles between the ribs are used to help us to breathe. Exhalation Inhalation Diaphragm relaxes and move up Diaphragm contracts and flattens Intercostal muscles relax Intercostal muscles contract Ribcage moves down and in Ribcage moves up and out Chest volume decreases Chest volume increases The heart Oxygen and food are carried to all the body’s cells by blood vessels. The heart pumps blood round the body. Facts about the heart 1. 2. 3. 4. 5. 6. The heart is made of muscle. There are four chambers in the heart Right atrium Left atrium Left ventricle Left ventricle The coronary arteries supply food and oxygen to the heart muscle. When these blood vessels get blocked, you suffer a heart attack. Heart valves stop blood flowing in the wrong direction and allow blood to flow in one direction only. Valves are found between the atria and ventricles and, also, as the blood leaves the heart, in the aorta and the pulmonary artery. The ventricles have thicker walls than the atria. The left ventricle has a thicker wall than the right ventricle because the left ventricle has to pump blood right round the body whereas the right ventricle only has to pump blood to the heart. A pulse indicates that blood is flowing through an artery. Blood flow through the heart Deoxygenated blood is blood low in oxygen returns to the heart via the vena cave. After travelling to all parts of the body, it enters the heart at the right atrium. The right ventricle then pumps blood out through the pulmonary artery to the lungs. In the lungs, the blood picks up oxygen and loses carbon dioxide. The oxygenated blood then returns to the heart via the pulmonary vein, entering the left atrium. The left ventricle pumps blood out through the aorta to the body. Arteries, veins and capillaries Blood is carries away from the heart in arteries. These arteries carry blood to the body’s organs and tissues. In the organs the arteries split up into a network of tiny tubes called capillaries. Substances are exchanged between the capillaries and tissues. Blood leaves the tissues in vessels called veins that carry the blood back to the heart. More about capillaries The capillary network allows efficient exchange of gases, food and waste because 1. They are narrow and thin walled which gives a greater surface area to allow fast diffusion of gases etc. 2. They are very long which also increases surface area. 3. No cell is ever far away from a capillary thus ensuring easy exchange of substances. Red blood cells and plasma Blood is made up of cells floating in liquid called plasma. The plasma also carries dissolved substances such as carbon dioxide, digested food and waste products. Red blood cells carry oxygen. Haemoglobin A red blood pigment called haemoglobin is found in red blood cells. Its function is to combine with oxygen to form oxyhaemoglobin. At the lungs haemoglobin haemoglobin combines with oxygen to form ox haemoglobin. At the tissues, oxyhaemoglobin releases oxygen and becomes haemoglobin again. At lungs Haemoglobin + oxygen --------------- oxyhaemoglobin -------------At tissues Gas exchange at the tissues Oxygen diffuses from the high concentration in the blood across into the body cells. Carbon dioxide diffuses from the high concentration in the tissues into the blood. C Coordination The eye The eye is the sense organ that you use to detect light. Part of the eye Function Cornea Tough but transparent layer Lens Focuses light on to retina Iris Coloured muscle that controls how much light gets into eye Retina Light detecting layer at back of eye; converts light to nerve impulses Optic nerve Carries nerve impulses to brain Judging distance with binocular vision As well as detecting pictures, your eye also allows you to judge distances. Your eyes are set in the front of your head. This gives you binocular vision which allows you to see things in three dimensions. Each eye sees the object slightly differently and two messages are sent to the brain which puts these two pictures together so that the object does not look flat. The Ear The ear is the sense organ you used to detect sound. cochlea Part of the ear Function Eardrum Thin membrane which vibrates when sound reaches it Middle ear bones Transmit vibrations across to cochlea Cochlea Converts vibrations to nerve impulses Auditory nerve Carries nerve impulses form cochlea to brain Semi circular canals Sends messages to brain re head movements; these impulses help to control balance The direction of sound Your ears, as well as detecting sound, can also help you judge the direction from which the sound is coming. Two ears are better than one at detecting the direction of sound. The sound of a ringing bell arrives at the left ear slightly faster then the right ear, thus giving an indication from where the sound is coming. Balance Your semi circular canals help you to balance. The semi circular canals are three fluid-filled tubes arranged at right angles to one another. This so that, when the head moves, fluid in one or more of the tubes will move. Information is sent from here to your brain to control your balance. The nervous system The nervous system is composed of the brain, the spinal cord and nerves. The brain sorts out information. The spinal cord sends information to the brain. The brain and spinal cord together make up the central nervous system (CNS). Sensory nerves carry information from the senses to the CNS. The CNC sorts this information out and then sends messages via motor nerves to the appropriate muscles which then contract. The brain The brain is the control centre of the nervous system. The brain is made up of three main parts: the cerebrum, the cerebellum and the medulla. Part of the brain Function Cerebrum Site of conscious thought, memory and intelligence Cerebellum Controls balance and muscular coordination Medulla Controls the rate of breathing and the heart rate Reflex Actions A reflex action is a rapid, automatic response to a stimulus. It is an involuntary action which does not always involve the brain. Reflex actions happen so quickly that there is often no time for the nerve impulses to reach the brain. Often the impulse only goes to the spinal cord and the brain becomes aware of the action only after it has happened. Relay neurone The reflex arc is an arrangement of nerve cells that makes sure you react quickly to hazardous stimuli. Some examples of reflex actions are pupils contracting in bright light, knee jerk and blinking. Sensory nerves cells send a message to the spinal cord. A relay nerve connects the sensory nerve to the motor nerve in the spinal cord. A message is sent down the motor nerve to make a muscle contract. D Changing levels of performance Aching muscles If you exercise for very hard or for a long time, eventually your muscles will ache. This is because they are not getting enough oxygen and because a waste product called lactic acid has built up in the muscles. This is called muscle fatigue. Anaerobic respiration in muscles If not enough oxygen is available for your muscles to carry out aerobic respiration, they are able to switch to anaerobic respiration to allow you carry on using the muscles for a while longer. Instead of producing CO2 and water as in aerobic respiration, your muscles produce lactic acid. This build up of lactic acid makes your muscles ache. With enough O2 glucose + O2---- CO2 + water With no O2 glucose ---- lactic acid How exercise affects pulse rate and breathing rate After exercise the breathing rate will increase. This is so that more oxygen is absorbed at the lungs. After exercise the pulse rate will increase. This is so that more food and oxygen van be carried to the muscles. The time taken for your heart rate, breathing rate and lactic acid levels to return to normal after exercise is called the recovery time. The time taken to recover is an indication of how fit you are. In general the longer it takes for your body to recover, the less fit you may be. The effect of training on fitness A trained athlete’s heart rate and breathing rate are usually lower than and untrained or unfit person. Another result of training is that and athlete’s heart and breathing rate do not increase as much as an untrained person during exercise. Therefore it is fair to say that training improves the efficiency of the heart and lungs. Also training lessens the recovery time.