THE MUSCULAR SYSTEM. Functions of Muscles. Types of Muscles

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1 1 THE MUSCULAR SYSTEM Muscles are tough elastic tissues made of cells called muscle fibres 656 muscles of the body account for 40% of the body s weight The Nervous System controls the action of muscles The circulatory system supplies the muscles with a rich blood supply which provides fuel for muscles. Functions of Muscles Muscles: Allow human movement Allow the development of strength, endurance and speed Help other body systems to do their work Protect and keep in place our abdominal organs Enable us to maintain good posture Help in the circulation of our blood Generate body heat when they contract Types of Muscles There are three types of muscle: Skeletal or Striated Muscles are also known as voluntary muscle because they are controlled consciously when the person decides to move. These muscles have many large, long, cylinder shaped, crossed-banned fibres each with many nuclei. The muscle ends are attached to bones by tough, flexible, connective tissue called tendons. Skeletal muscles form much of the legs, arms, chest, neck and face. They hold bones together and pull on them to make them move. Smooth Muscles are also called involuntary muscles because they work automatically. Their fibres are smaller than skeletal muscles; not striped, and with a single nucleus. They are arranged with connective tissue in continuous sheets. Smooth muscles are found in the intestines, stomach, bladder, alimentary canal, arteries, arterioles and iris diaphragm of the eye. Cardiac Muscles are also involuntary muscles because they work automatically. These muscles form the major part of the heart, and contracts and relax continuously to provide the pumping action.

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4 4 Locating the different types of muscles 1. Colour the organs with smooth muscles yellow. 2. Colour the organs with cardiac muscles red. 3. Colour the skeletal muscles blue.

5 Major Skeletal Muscles 5

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7 7 Muscle Trapezius Deltoid Pectorals Intercostal Muscles Abdominals Latissimus Dorsi Biceps Triceps Gluteals Quadriceps Hamstrings Gastrocnemius Main Actions Helps control the shoulder girdle Moves the head back and sideways Moves the arms in all directions Adduct the arm at the shoulder Used for deep breathing Moves the ribcage during breathing Rotate and raise the trunk Strengthens the abdominal wall Adduct and extends the arm at the shoulder Flexes the forearm at the elbow Extends the forearm at the elbow Extends the arm at the shoulder Abduct and extend the hip joint Flexes the hip joint Extends the knee joint and keeps it straight when standing Extends the hip joint Flex the knee joint Flexes the knee joint Points the toes Muscle Attachment to Bones Muscles are attached to bones by tendons. Tendons are strong flexible cords at the end of muscles. Tendons are fixed deeply into the bone and are very strongly attached. Tendons vary in shape and size. Some muscles are divided into more than one part and may end in two or more tendons, which may be fixed to different bones; e.g. biceps and triceps. Muscles make the bones around a joint move. Usually one bone stays fixed and the other moves. The end of the muscle that is attached to the fixed bone is called the origin (1). The end of the muscle that is attached to the bone which moves is called the insertion (2). How Muscles Work Muscles pull when they contract they do not push. A contraction is the shortening and bulging of a muscle. When muscles relax they return to their original length

8 8 Types of Contractions There are two main types of contractions Isotonic contractions Isometric contractions An Isotonic contraction is the change in length of a muscle and occurs when any part of the body moves. There are two types of isotonic contractions: A Concentric contraction is the shortening of a muscle. The ends of the muscle moves closer together. An Eccentric contraction is the gradual controlled release of a muscle contraction. The ends of the muscle moves further apart. When the arm bends a concentric contraction occur in the biceps and an eccentric contraction occur in the triceps When the arm straightens an eccentric contraction occur in the biceps and a concentric contraction occur in the triceps An Isometric contraction does not change the length of a muscle and do not cause movement. The muscles stay the same length and the ends of the muscle stays the same distance apart. When holding the shot putt in place an isometric contraction occurs in both the biceps and triceps.

9 9 The Role of Muscles in Movement Muscles work in pairs. When one muscle contracts to bring two bones together another muscle is needed to pull the bones apart. When a movement takes place one muscle contracts while another relaxes. Muscles take on different roles depending on the movement that is being performed. When muscles: contract to cause a movement they are called Prime Movers. relax to allow a movement they are called Antagonists. contract to steady parts of the body to give the working muscles a firm base they are called fixators. contract to reduce unnecessary movement when a prime mover contracts or refine a movement they are called synergists. Muscles are also named according to the role they play in movement: Flexors are muscles that bend a limb at a joint e.g. Biceps and Hamstring. Extensors are muscles that straighten a limb at a joint e.g. Triceps and Quadriceps Adductors are muscles that move a limb towards the midline of the body e.g. Latissimus Dorsi and Pectorals Adductors are muscles that move limbs away from the midline of the body e.g. Deltoid and Gluteals Muscle Tone Muscle tone is the tension of the muscular system. It is the state of readiness of the muscular system to do its job. When we are not moving some muscle fibres are contracted while others are relaxed. These contractions tighten the muscles a little, but are not strong enough to cause movement. Different fibres contract at different times in order to prevent tiredness setting in. Muscle tone is not constant but decreases in time of relaxation and increases dramatically in states of excitement such as fear, anger or stress. Poor muscle tone leads to posture defects, loss of strength and loss of muscle endurance, and makes recovery from disease or injury harder. Exercise increases muscle tone.

10 Muscle Fibres Muscles are made up of tiny threadlike fibres packed together in bundles. Skeletal muscles consist fast twitch fibres and slow twitch fibres. 10 Slow-twitch muscle fibres: have a very good oxygen supply work for a long time without tiring are not as strong as fast-twitch fibres take longer to contract are used in all types of exercises are used especially in aerobic activities Fast-twitch muscle fibres: do not have a good oxygen supply tire very quickly are stronger than slow-twitch-fibres contract very quickly are used for fast, powerful movements are used only in high-intensity exercises are used in anaerobic activities How muscle fibres work Muscles are usually an equal mixture of fast and slow twitch muscles. When jogging slowly, only a few slow twitch fibres contract to move the legs. When the speed is increased more slow-twitch fibres are used. As running becomes faster, fast-twitch fibres also start to contract to help out and more and more will start to work as running speed increases. At top speed all fast and slow twitch muscle fibres will be working. Many sports require the use of the different fibres at different times. For example, in football slow-twitch muscle fibres are used for jogging when not involved in the action and fast-twitch fibres are used for quick sprints. A person with more slow-twitch muscle fibres is more likely to be better at sports needing endurance such as cycling, running and swimming. A person with more fast-twitch muscle fibres is likely to be better at sprinting, throwing and jumping. Muscle fibres can be trained to contract more often (slow-twitch) or more powerfully (fast twitch).

11 11 Posture Posture is the way the body is held when sitting, standing or walking. Good posture is achieved by keeping our centre of gravity over our base of support so that most of our weight will be supported by the bones and the muscles help only a little to hold us upright. Good muscle tone in the lower back, leg and abdominal muscles will help muscle tone. Good Posture: Reduces the strain on our muscles, tendons and ligaments Allow our body systems to work more easily and makes us less tired Improves coordination Increases general health and confidence Poor Posture: Cause muscle and ligament strain Can lead to problems such as stiff neck, headaches, back ache, and displacement of internal organs Good Posture when standing Head balanced over body; chin in, back and neck stretched upwards Shoulders held straight, easily not stiffly Chest slightly up and forward Abdomen flat Pelvis level and balanced over feet Knees straight and relaxed, neither bent nor forced back Feet comfortably apart, weight evenly balanced, toes facing Ahead Ear, shoulder, hip and ankle should form a straight line Good Posture when sitting Feet flat on the floor, knees bent at approximately at 90 o. Height of seat should be adjusted to correspond to the length of the lower legs The seat should support thighs close to the back of knee Sit back in the chair to support the lower back When writing at a desk bend forward at the hips, and use the back rest occasionally to support the trunk Desk height should allow for forearms to rest comfortably without effort from the shoulder muscles Have a break every 20 minutes to gently exercise the arms and shoulders

12 12 Good Posture when walking Toes pointed ahead, feet parallel or with toes slightly pointing outwards Steps should be even, natural and rhythmic Arms swing easily and naturally Head is carried tall and straight without straining Do not drag legs or feet Good Posture when lifting Do not bend forward without bending the knees Keep the back flat and straight Bend at the hips and knees Keep the load close to the body Do not bend over the load Try to avoid lifting anything above the level of the elbows Extend the legs in order to lift objects Keep head up and eyes looking forward Effect of Exercise on the Muscular System During Exercise Blood flow to the working muscles is increased Muscles take up more oxygen from the blood Muscles contract more often and quickly More muscle fibres contract The temperature in the muscles rise Stores of ATP (adenosine triphosphate) and CP (creatine phosphate) in the muscles are used up Waste products such as carbon dioxide and lactic acid build up in the muscles Muscle fatigue sets in because of the build up of waste products Stores of glucose in the muscles are used up Our ability to carry on will be affected Overuse of muscle can lead to soreness and tiredness Over Time- due to a regular strength training programme Hypertrophy - Muscles increase in size and strength Muscle tone increases Lack of exercise cause muscles to: Atrophy get smaller and weaker (this also happens when recovering from an injury Decreases muscle tone