Describe (P2) and explain (M2) how the skeletal system responds to exercise. (P2, M2)
The condition of bone may be improved by exercise as it responds to mechanical stresses. These mechanical stresses usually take the form of pulling at their points of attachment being their origins and insertions. Where these mechanical stresses are applied, most it has been shown that more mineral salts are deposited and more collagenous fibres are produced. Therefore, both the density and size of bone in these areas may be increased and these changes in bone structure are stimulated by increased loads being placed on the skeleton. This has been borne out by greater bone mass being observed in weight lifters than in other lighter endurance athletes such as joggers. Other examples include racquet players who have been shown to have greater bone density in their playing arms. It has even been shown that if a leg is immobilised by being placed in plaster, due to a fracture, that even after a few weeks the bone becomes decalcified from lack of mechanical stress.
Whilst it may therefore be considered beneficial to utilise exercise to maintain healthy bones, great care must be taken with children whose bones and muscles are still developing. They should not be subjected to forms of sport involving high degrees of mechanical stress, partly because of the weaknesses that still exist within the bones, and also because of adverse effects on the development of these bones before maturity.
There are two main effects on bones as we grow older. Bones begin to lose calcium and this is one of the factors contributing to the condition called osteoporosis. Secondly, with age less protein is produced which alters the make-up of bone and sometimes creates brittle bones.
Explain why different classifications of joints allow different ranges of movement. (M1)
There are three different types of joints. These are as follows:
A fixed joint is a joint between two bones that does not move. A good example of this is in the skull - the skull plates do not move together or against each other, but they are connected or fused.
This type of joint allows no form of movement and as such has no range of movement. This is because it is used to protect a vital organ such as how the cranium, a fixed joint, is used to protect the brain, a major organ.
These joints are firmly held together by a thin layer of strong connective tissue. There is no movement between the bones such as the sutures of the skull and the teeth in their sockets.
A cartilaginous joint allows some slight movement. The ends of bones, which are covered in articular or hyaline cartilage, are separated by pads of white fibro cartilage and slight movement is made possible only because the pads of cartilage compress.
In addition, the pads of cartilage act as shock absorbers.
The intervertebral discs are examples of this type of joint.
This type of joint moves very little but not enough to have a range of movement. This is because they are normally found around vital organs similarly to that of the fixed joint like example the spinal cord.
Cartilagenous joints are joints where the articular surfaces of the bones forming the joints are attached to each other by means of white fibrocartilaginous discs and ligaments which allow only a limited degree of movement. Examples are the cartilaginous between the vertebrae, the cartilage in the symphysis which binds the pubic bones together at the front of the pelvic girdle and the cartilage in the joint between the sacrum and the hip bone.
- Freely movable/synovial joints-
A synovial joint is a freely moving joint, and is the most common type of joint in the body, and the most important in terms of physical activity, since they allow a wide range of movement. These types of joint are divided up according to the movement that they make possible.
Surrounding the joint is a membrane called the Synovial Membrane which is where Synovial fluid is formed. This fluid acts as a lubricator and is formed within the joint AND allows friction free movement.
A good example of this is the knee joint.
This type of joint allows 5 ranges of movement at a particular joint. This is to allow the participant to perform actions. These ranges of movements are:
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Adduction- this movement brings part of the body towards the centre of the body. Adduction is adding to the body.
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Abduction- this is the opposite action of adduction. The limbs are abducted from the centre of the body. This means taking away.
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Flexion-closing the angle at a joint. For example when throwing a ball the angle at the elbow is decreased.
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Extension- this is the opposite f flexion. It is when the angle increases between the bones at a joint.
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Rotation- the angles do not change but the joint moves in a circular motion.
These are freely movable joints. Most of the joints in the body are of the synovial type. The following are the main characteristics of a synovial joint:
- The ends of the bones are covered with a layer of smooth hyaline cartilage, called articular cartilage in the joint regions. This reduces fricton at the point.
- The joint is completely enclosed by a bag-like capsular ligament which holds the joint together and helps to contain the synovial fluid.
- The capsular ligament is lined with a synovial membrane. This membrane secretes synovial fluid into the synovial cavity and acts as a seal, waterproofing the joint. The synovial fluid lubricates the joint.
- In addition to the capsule, the bones are also attached and held together by strong, tough ligaments made of dense connective tissue. These ligaments prevent dislocation during normal movement.
- The articulating surfaces of adjacent bones are reciprocally shaped.
Synovial joints can be subdivided into the following groups according to the type of movement they carry out:
These joints are formed where the rounded head of one bone fits into the hollow, cup-shaped socket of another bone such as the shoulder joint and the hip joint. Such joints allow freedom of movement in all directions.
These joints occur where the convex surface of one bone fits into the concave surface of another bone, so making movement possible in one plane only. Examples of these joints are the knee and the elbow joints. Hinge joints have ligaments mainly at the sides of the joints. These ligaments prevent lateral movement and dislocation, allowing only flexion and extension.
This type of joint allows for gliding movements between flat surfaces as the surfaces slide over one another. Only a limited amount of movement is allowed such as the joints between the carpal bones, the joints between the tarsal bones and those between the articular processes of successive vertebrae.
A bony ring rotates round the pivot (axis) of another bone. This allows the head to turn from side to side. E.g. the neck.
These joints are made up of several joints between a numbers of different bones. The bones articulate with one another in different ways, allowing for a variety of movements such as the set of joints which operate the movement of the skull on the vertebral column. The condyles at the base of the skull fit into the facets of the atlas, allowing for the nodding movement of the head. While one moves one's head, the atlas is able to rotate round the odontoid process of the axis, allowing the head to turn from side to side. There are also other articulating surfaces, where the atlas and axis meet. All these joints together make a compound joint with its many possible movements in the neck region.
Analyse how the skeletal system responds to exercise. (D1)
Vital at every age for healthy bones, exercise is important for treating and preventing osteoporosis. Not only does exercise improve your bone health, it also increases muscle strength, coordination, and balance, and leads to better overall health.
Like muscle, bone is living tissue that responds to exercise by becoming stronger. Young women and men who exercise regularly generally achieve greater peak bone mass (maximum bone density and strength) than those who do not. For most people, bone mass peaks during the third decade of life. After that time, we can begin to lose bone. Women and men older than age 20 can help prevent bone loss with regular exercise. Exercising allows us to maintain muscle strength, coordination, and balance, which in turn help to prevent falls and related fractures. This is especially important for older adults and people who have been diagnosed with osteoporosis.
The best exercise for your bones is the weight-bearing kind, which forces you to work against gravity. Some examples of weight-bearing exercises include lifting weights, walking, hiking, jogging, climbing stairs, tennis, and dancing. Examples of exercises that are not weight-bearing include swimming and bicycling. While these activities help build and maintain strong muscles and have excellent cardiovascular benefits, they are not the best way to exercise your bones.
Short term effects
Short term effects on the skeletal system are demonstrated by changes within the joint. Movement of joints stimulates the secretion of synovial fluid. This fluid becomes less thick and the range of movement at the joint increases. With regular exercise, connective tissue improves in flexibility. Long-term responses of the skeletal system to exercise include maintenance of the improved range of movement around your joints.
Increased mineral content
Your bones are not static. They can become stronger and denser as a result of the demands you place on them through physical activity and exercise. Physical activity and exercise and increase the mineral content of your bones. They key factor regulating this is the mechanical force you apply during the activities you undertake. The types of exercise that help build stronger bones are strength training and weight-bearing exercises that work against gravity with differing degrees of impact, such as tennis, netball, basketball, aerobics, dancing, walking and running. You bones are strengthened as a result of the stress exercise imposes on them, which results in greater quantities of calcium and collagen being deposited within them. This helps to reduce the risk of osteoporosis. A strengthening in the supportive connective tissue surrounding your joints also occurs.
Thickening of the hyaline cartilage
Hyaline cartilage becomes thicker with regular exercise. This is the most common type of cartilage in the body. It is found mainly on the articulating surfaces of the bones and protects the bone surfaces from wear and tear. It also provides a certain amount of elasticity to absorb shock. It connects the ribs to the sternum and is found in certain structures of the respiratory system. This type of cartilage can become calcified with advancing age.
Task 2
Describe the muscular system, including all the major muscles, and how muscles move. (P3)
The muscular system is composed of specialized cells called muscle fibres. Their predominant function is contractibility. Muscles, where attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of , the on sperm cells, and movement of some white blood cells.
The integrated action of joints, bones, and skeletal muscles produces obvious movements such as walking and running. Skeletal muscles also produce more subtle movements that result in various facial expressions, eye movements, and respiration.
In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability. This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint. Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction.
A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle, in some they converge to a narrow attachment, and in some they are oblique.
Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.
Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves.
Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction.
Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries.
In the body, there are three types of muscle: skeletal (striated), smooth, and cardiac.
Skeletal Muscle
Skeletal muscle, attached to bones, is responsible for skeletal movements. The peripheral portion of the central nervous system (CNS) controls the skeletal muscles. Thus, these muscles are under conscious, or voluntary, control. The basic unit is the muscle fiber with many nuclei. These muscle fibers are striated (having transverse streaks) and each acts independently of neighboring muscle fibers.
Smooth Muscle
Smooth muscle, found in the walls of the hollow internal organs such as blood vessels, the gastrointestinal tract, bladder, and uterus, is under control of the autonomic nervous system. Smooth muscle cannot be controlled consciously and thus acts involuntarily. The non-striated (smooth) muscle cell is spindle-shaped and has one central nucleus. Smooth muscle contracts slowly and rhythmically.
Cardiac Muscle
Cardiac muscle, found in the walls of the heart, is also under control of the autonomic nervous system. The cardiac muscle cell has one central nucleus, like smooth muscle, but it also is striated, like skeletal muscle. The cardiac muscle cell is rectangular in shape. The contraction of cardiac muscle is involuntary, strong, and rhythmical.
Smooth and cardiac muscle will be discussed in detail with respect to their appropriate systems. This unit mainly covers the skeletal muscular system.
Muscle pairs
Antagonistic muscle pairs
The muscles do not work in isolation. They are assembled in groups and work together to bring about movement. They act only by contracting and pulling. They do not push, although they are able to contract without shortening, and so hold a joint firm and fixed in a certain position. When the contraction passes off the muscles become soft but do not lengthen until stretched by the contraction of the opposite muscles. They can act in the following ways to bring your body in to action.
The muscle that shortens to move a joint is called the agonist or prime mover. This is the muscle principally responsible for the movement taking place-the contracting muscle.
The muscle that relaxes in opposition to the agonist is called the antagonist. This is the muscle responsible for the opposite movement, and the one that relaxes as the agonist works. If it did not relax, movement could not take place. Antagonists exert a ‘braking’ control over the movement.
Synergists are muscles that work together to enable the agonist to operate more effectively. They work with the agonist to control and direct movement by modifying or altering the direction of pull on the agonist to the most advantageous position.
Theses muscles stop any unwanted movement throughout the whole body by fixing or stabilizing the joint or joints involved. They also help to maintain posture.
Types of contraction
In this type of contraction, no change in muscle length takes place. It occurs when a muscle is actively engaged in holding a static position, for example when stopping halfway up in a press up or squat position, or holding an abdominal plank position. With this type of contraction, the origin and insertion do not move and no movement occurs at the respective joint. This type of muscle work is easy to undertake but rapidly leads to fatigue and can cause sharp increases in blood pressure as blood flow is reduced. Strength gains achieved are also limited to the range in which the training has occurred.
This occurs when a muscle shortens against a resistance, for example in a bicep curl. The brachialis and bicep shorten, bringing your forearm towards your upper arm. Another example is the knee extension, perhaps straightening the leg on a leg extension machine in the gym. The quadriceps is the muscles that contract to extend the leg. Concentric contractions are sometimes known as the positive phase of muscle contraction.
This occurs when a muscle returns to its normal length after shortening against a resistance. Using the bicep curl as an example, this is the controlled lowering of your arm to the starting position. At this point your muscles are working against gravity and act like a breaking mechanism. In the leg extension example, this is the lowering of the weight back to the bent-leg starting position. This contraction can be easier to perform but it does produce muscle soreness. Eccentric contractions occur in many sporting and daily activities. Walking down the stairs and running downhill involve eccentric contraction can be a significant factor in the stimulus that promotes gains in muscle strength and size. Eccentric contractions are sometimes known as the negative phase of muscle contraction.
Muscle tone and posture
Muscle tone can be seen when muscles are in a state of slight tension and they are ready for action. Regular training tones muscles and helps to create good . In addition, muscles will hypertrophy (increase in size) and develop better .
Muscle tone developed by regular exercise makes daily tasks such as shopping and gardening easier. It also helps to prevent injury as good posture reduces the strain on muscles, tendons and ligaments.
Good posture helps with sporting performance as special positions are often crucial to success, eg the position throughout the golf swing.
People with good posture also feel better about themselves. An upright body position is often a sign of self confidence. People who are less confident will sometimes show this in their body language, for example by adopting a slouched posture.
Sliding filament theory of muscular contraction
Your individual muscle fibres are long, cylindrical, multinucleated cells that vary in length and breadth. The structures of individual muscle fibres, working from the outside inwards, include:
- Endomysium: this forms the fibrous sheath around the outside of the fibre.
- Sacrolemma: the cell membrane that binds the muscle fibre. It lies below the endomysium just above the nuclei of the cell.
- Sacroplasm: the cytoplasm of the muscle cell. This is where the mitochondria are housed.
- Myofibrils: tiny thread-like structures. These run the length of the muscle fibres and make up much of its bulk. These are the elements that contract and relax.
- Myofilaments: these contain thin filaments called actin (small thread-like structures) and thick filaments called myosin. These myofilaments are contained in functional units called sarcomeres. When the stimulus to contract is received by the muscle fibre, actin and myosin slide over each other, decreasing sacromere length.
Each muscle fibre contains several hundreds or thousands of myofibrils. The sarcomeres of the myofibrils within a single muscle fibre are aligned. When viewed under a microscope, stripes or striations can be seen along the length of the fibre. These alternate light and dark bands overlap.
When the muscle contracts, the degree of overlap between the thick filaments (myosin) and thin filaments (actin) increases, causing the filaments to creep along each other via tiny cross bridges that extend from myosin filaments. The sliding of the actin filaments results in a reduction in the length of each myofibril. This process takes place within all fibres, causing the whole muscle to shorten.
Describe (P4) and explain (M3) how the muscular system responds to exercise (P4, M3)
Your muscles will twitch using energy in the form of glycogen break down and turn catabolic initially during and right after exercise. This means it is breaking down nutrients to restore glycogen levels depleted due to exercise. When you start consuming more food than your body needs to function, it will begin repairing the muscles throughout the hours after exercise and for the next few days (anabolic protein synthesis). (Making new muscle tissue from nutrients to replace the torn fibres). When you surplus on calories, hypertrophy occurs which is when your muscles actually grow larger. By the time the muscles are healed (repaired) you are ready to tear them up with some more exercise again
The muscles respond by physically adapting to the stresses, activity, resistance and weight load that is imposed on them. They change according to size, mass, strength, power, to be able to cope with the task that are asked of them. The activity that the muscles have to do, the muscles will slowly get used to this workload and adjust according to the FITT rule - frequency, intensity, time and type.
The heart as a muscle and the most important of them all will function in able to work hard to pump our blood around our bodily systems and to the other muscles in order for them to carry out every single task they do.
Mention that your muscles become physically and visually more toned, stronger and have less chance of becoming fatigued. The more stress you impose on the muscle more they can start to cope with it.
Analyse how the muscular system responds to exercise. (D2)
Short term
The short term effect s of exercise on the muscles include an increase in temperature and metabolic activity. As a result of this increase in metabolic activity, there is a greater demand for oxygen met by an increase in blood supply throughout capillary dilation.
Muscle damage
The warming of your muscles during activity makes them more pliable and reduces the risk of muscle damage and injury.
Long term
The long tern responses and adaptations of the muscles to exercise depend on the type and frequency of sport and exercise training undertaken and the overload achieved.
The strength and bulk (hypertrophy) of the muscles increase in response to a programme of progressive resistance training. This is largely due to an increase in the actin and myosin filaments in the muscle cell, making the muscle fibres thicker. Flexibility training leads to an increase range of movement around your joints. The endurance of the muscles also improves, allowing them to contract for longer while resisting fatigue and facilitating better muscle tone, shape and posture. The muscles need to be kept in continuous use for them to remain in good condition. If they are not exercised regularly, they become weak and their capacity for work is reduced.
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Increased strength of tendons
Tendons are tough bands of fibrous connective tissue that are designed to withstand tension. Like muscles, tendons adapt to the mechanical loading of regular exercise. A general adaptation is in the increased strength of the tendons but different types of training result in different effects.
Learning Outcomes
1 Understand the structure and function of the skeletal system and how it responds
To exercise
2 Understand the structure and function of the muscular system and how it
Responds to exercise
Grading criteria assessed P1, P2, P3, P4, M1, M2, M3, D1, and D2