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Muscoskeletal Systems and Physiology of Exercise
- Explain what ossification is and what it involves. 150 words.
Ossification is the process by which bone is formed, and is divided into two types:-
Intramembranous ossification occurs within the first five weeks of foetal development; in primary centres where the beginning of bone formation occurs, involving development of the skull, clavicle, upper and lower jawbones and patellas. They begin as mesenchyme connective tissue containing stem cells that differentiate into osteoblasts (bone-forming cells), and then a build up of calcium levels occurs to help form bone tissue, which is added layer upon layer, called lamellas, until the outer lining called the periosteum is formed, and the initial mesenchyme becomes bone marrow.
Endochondral ossification occurs after five weeks of foetal development, and during childhood, when the primitive connective tissue mesenchyme has converted to cartilaginous models in secondary centres, involving the lengthening of bones and the formation of long, short, flat and irregular bones of the skeleton. Both types of ossification are also used for the healing of bone fractures.
- Describe the functions of the skeleton. 200 words.
The skeleton is comprised over over 200 bones that provides our structure and shape, determining whether we are tall or short, wide or narrow. The spine supports the torso when standing straight, and the legs support the body's weight. The thorax contains the rib cage which encases the heart and lungs, holding them in place and protecting our vital organs from possible injury; as does the skull for the brain, and the spinal colomn for the spinal cord.
The skeleton has muscles attached to some bones forming the muscoskeletal system that allow movement when the muscles contract, and therefore enables the body to sit, walk, lay down, lift, run, and throw.
The skeleton not only gives support and protection, but is also important for certain bodily functions, including the production of red blood cells in the bone marrow that transport oxygen around the body. The production of minerals such as calcium and phosporus that are used for metabolism and nerve transmission. The regulation of the endocrine system, controlling blood sugars, fat distribution and helping prevent type 2 diabetes; as well as electrolyte balance and acid-base balance.
- Identify the joints in the diagram below, and explain the reasons for your answers. 200 words.
Pivot Joint – between the atlas and axis (first and second vertebrae) in the neck. One rounded end bone pivots within a ring shaped bone formation, allowing one rotary movement.
Ball and Socket Joint – the shoulder. Also called spheroidal joint, where the rounded end of one bone moves within a cup shaped dent on another bone, allowing the most freedom of movement of all joints.
Hinge Joint – the elbow. Allows movement in only one plane through the pair of collaterol ligaments situated either side of the joint, where only one of the bones move.
Ellipsoid Joint – the wrist. An oval shaped end of one bone fits into an oval shaped cavity of the other bone aloowing all angular movements but no axial rotation. Also called condyloid joint.
Saddle Joint – carpometacarpal joint of the thumb. One flat bone shaped like a saddle with another bone resting on the top like a horserider, providing stability to bones whilst providing more flexibility that a hinge or gliding joint.
Gliding Joint – between the tarsal (ankle) and metatarsals of the foot. Bones that meet at flat or almost flat articular surfaces, allowing the bones to glide past one another in any direction along the plane of the joint and also to slightly rotate.
- Discuss the structure of a named synovial joint. 200 words.
Ball and Socket Joint
A synovial joint found in the shoulder and hip of the human body. The shoulder contains the “ball”, the rounded end of the humerus which sits in the “socket”, a cup-shaped recess called the glenoid fossa, which is formed in the scapula. The hip contains the “ball”, the rounded end of the femur which sits in the “socket”, a cup-shaped recess called the acetabulum, which is formed in the pelvis.
Both of these joints contain between the bones a layer of hyaline cartilage which reduces friction and acts as a shock absorber, surrounding a synovial membrane that produces synovial fluid which acts as a lubricant during movement. Muscles attach to these bones by tendons enabling movement when the muscles contract, and ligaments attach bone to bone to stabilise the joint.
The ball-and-socket-joint is the most mobile type of joint, and allows the humerus and femur to move outwards from the body (abduction), inwards towards the body (adduction), forward (flexion, backward (extension) and around the joint in a full circle (circumduction); as well as medially and laterally rotating around their axis.
- Explain the structure of a voluntary muscle, using a fully labelled and referenced diagram. 150 words.
A voluntary muscle is also known as a skeletal muscle as they are usually attached to bones, forming part of the muscoskeletal system. The muscles work in opposing pairs with the extensor (contracting muscle) and the flexor (expanding muscle) enabling controlled movement. The muscles comprises muscle cells that are long and almost cylindrical in shape, which fuse together into fibres that run the length of the muscle, derived from two types of proteins; myosin and actin, that alternate in thick and thin bands giving a striped, or striated, appearance.
These fibres form into bundles called fasciculi which are each surrounded by a layer of connective tissue called the perimysium. Each muscle fibre is covered in a connective tissue called endomysium for insulation. All of this, and blood vessels, are contained within the epimysium which is the outer layer of connective tissue that protects the muscle from friction and forms part of the tendon that attaches the muscle to the bone.
2. Explain a tendon, using a fully labelled and referenced diagram. 150 words.
A tendon isa tough cord of fibrous connective tissue, capable of withstanding tension. It is made of multiple layers of strong and flexible collagen fibres that are arranged in tightly packed parallel bundles, which help to maximise its strength. This cord extends out of the muscle, being entwined with the muscles connective tissues, and attaches to the periosteum; a layer of connective tissue that surrounds bone. Tendons can also attach to other structures than bone, such as eyeballs.
Tendons play an important part in muscle control of the body as contraction of the muscle pulls on the tendon, causing the tendon to pull and move the bone. Tendons create a connection between bone and muscle that is hard to break. They can be at risk of injury however due to them being tightly stretched connecting the muscle to the bone. Severe stretching can cause the tendon to tear. They can also become inflamed if repeatedly over-used.
- List the different types of muscle fibres.
Type I 'slow twitch fibres'
Type IIa 'fast twitch oxidative fibres'
Type IIb 'fast twitch glycolytic fibres'
- For each of the muscle fibres listed above, explain how their properties rely on aerobic and anaerobic respirations. 500 words
Many muscles need to be able to perform effectively in many different endurance functions, and the type of muscle fibre the body uses depends on the type of activity the body is doing. These muscle fibres consist of both slow and fast contracting types. For a muscle to contract it needs energy, which comes from the oxygen in the blood during aerobic respiration, and from stored carbohydrates during anaerobic respiration.
Type I 'Slow twitch' muscle fibres contain a large amount of blood capillaries containing oxygen and lots of mitochrondria that are responsible for keeping the muscle cells full of energy. The myelin sheath that surrounds the motor neurone stimulating the contraction is thinner than those of the fast twitch fibres, which slows down the nerve impulse. They have the required enzymes to allow for aerobic respiration, and are able to break down fat and carbohydrates to carbon dioxide and water. This is a slower process than anaerobically releasing energy, and does not produce any by-products that may have a detrimental effect on the muscle. They therefore contract slowly but keep going for a long time, so are good for endurance activities like running marathons or cycling, as they do not generate a huge amount of force, but can offer sustenance as they are slow to tire with continual actions.
The fibres in Type IIb are known as fast twitch glycolytic (F.T.G.) which contract very quickly and powerfully, generating a lot of force in short bursts, which is ideal for very high intensity activities. They have much more powerful contractions than other muscle fibres, as they have a much larger motor neurone that carries the impulse which speeds up the contraction. The muscle fibres are thicker and bigger, and there are a greater quantity within a motor unit. They purely rely on anaerobic respiration as they only have a small amount of mitochondria.They are suited to speed, strength and power type activities such as weight training and sprinting, and they are good for rapid movements like kicking a ball or jumping, but become quickly exhausted.
Type IIa muscle fibres are known as fast oxidative glycolytic (F.O.G.) which provide a mixture of both Type I and II characteristics allowing for speed and endurance, which is ideal for sustained power activities such as running or boxing; as they use glycogen for their energy source which is a combination of oxygen and stored carbohydrates. They are considered aerobic as they use oxygen, but the levels are not as much as Type I fibres use. The stimulating motor neurone has a thicker myelin sheath than Type I, so it can contract quicker and exert more force, as there are more fibres in each motor unit. They can produce energy by breaking down carbohydrates to pyruvic acid; but are more suited to anaerobic respiration, which allows faster release of energy. This produces a rapid accumulation of lactic acid however, which lowers the Ph balance, and has a detrimental effect on the enzyme action which causes the muscle to tire.
TAQ 3: Factsheet on the impact of exercise on the cardiovascular, respiratory, muscular and skeletal systems.
Why Is Exercise Is So Beneficial?
Taking regular exercise impacts on our bodies in very positive ways. Just 30 minutes of medium to high intensity exercise, at least three times a week will make a difference to your shape, your strength, your vital organs and body systems, and help you live longer and healthier.
Impacts On The Cardiovascular System
- Growth of the heart muscles and blood vessels
- Growth in number of red blood cells
- Increase of oxygen and nutrients transported in the bloodstream
- Increase in collection of waste products and removal of toxins
- Increased immunity from germs and illness
- Regulation of metabolism
- Reduced risk of heart attack and stroke
Impacts On The Respiratory System
- Increase in strength of intercostal muscles and diaphragm
- Increase in number of alveoli
- Increased ability of the lungs to extract oxygen
- Increased lung capacity
- Reduces breathing difficulties
Impacts On The Muscular System
- Muscles contract more often and strengthen
- Increased blood flow to muscles
- Growth of muscles
- Increase in muscle endurance
- Strengthening of tendons and ligaments around joints
Impacts On The Skeletal System
- Joints become more resilient
- Increased flexibility in joints
- Increased bone width and density
- Increased bone strength
- Reduces risk of osteoporosis
Brain & General Wellbeing
- Promotes brain cell repair
- Lengthens attention span
- Improves memory
- Increases production of nerve cells and blood vessels
- Relieves depression, stress & anxiety
- Burns calories, depleting fat stores
- Weight loss
- Improves sleep patterns