S-Cool Revision Summary

S-Cool Revision Summary

The heart is a muscular pump that continuously and rhythmically beats to pump blood and its contents around the body and is made of cardiac muscle. It is dfivided into four chambers.

The two upper chambers are called atria and receive blood into the heart.

The two lower chambers are known as ventricles, again one on the left and one on the right and pump blood from the heart.

Both ventricle walls are thick and muscular especially the left ventricle wall as their contraction pushes the blood to the lungs and heart.

All four chambers are connected to their own blood vessel:

The right atrium - the vena cava

The left atrium - the pulmonary vein

The right ventricle - the pulmonary artery

The left ventricle - the aorta

Blood flows into the heart from the body and head into the right atrium through the vena cava. Blood from the lungs flows into the left atrium through the pulmonary vein. Blood from the right ventricle goes out through the pulmonary artery to the lungs. Blood from the left ventricle goes out through the aorta to the head and body.

When the body is at rest the heart can beat at between 50 to 80 times a minute, pumping the 4.7 litres or so of blood around the body.

The heart can respond immediately to any extra demands, for example, during exercise. Heart rate can increase to over 200 beats per minute, pumping 45 litres around the body in a minute.

Heart rate can be used to measure if the intensity of exercise is sufficient to improve fitness levels. This is dependent on the age of the person exercising and can be calculated in the following way:

75% of maximum heart rate

maximum heart rate = 220 - age

For example, a person who is 30 years old has a maximum heart rate of 220 - 30 = 190. 75% of 190 = 142.

Arteries carry freshly oxygenated blood from the heart to the capillary system.

One exception to this rule is the pulmonary artery that carries deoxygenated blood.

Most arteries lie deep in the body, but some are nearer the surface and it is these places that a pulse can be felt.

Artery walls are thicker than the walls of veins because they have a thicker layer of smooth muscle and elastic fibres between the protective covering and connective tissue.

Veins are often near the surface. Being near the surface allows any excess heat that is generated during exercise to be lost to the atmosphere. Veins have valves to prevent blood flowing backwards.

Capillaries are minute vessels with walls of only one cell thick. This allows food and oxygen to pass out to the body cells and carbon dioxide and other waste products to pass into the bloodstream.

Blood is a fluid tissue which provides a link between all the other tissues and organs of the body. It has the capacity to carry essential items around the body. Some of these items are:

  1. oxygen from lungs to body cells

  2. carbon dioxide from body to lungs

  3. waste products and water from cells to kidneys

Blood is pumped out of the heart under pressure.

Pressure is calculated by measuring the pressure needed to stop the flow of blood through an artery.

Two readings are taken, the systolic pressure when the heart contracts and the diastolic pressure when the heart relaxes.

Constant high blood pressure is known as hypertension.

Red Blood Cells:

  1. Contain haemoglobin that is a compound of protein and iron.

  2. Combine readily with oxygen to form a compound called oxyhaemoglobin.

  3. Combine with oxygen where oxygen is plentiful.

  4. Lose oxygen where oxygen is scarce, as in the body tissue.

  5. Are produced in the red marrow of long bones.

  6. Have no nuclei and wear out in 3 - 4 months.

White Blood Cells:

  1. Form a mobile guard and repair system to keep disease from the body.

  2. Are made in the bone marrow, the lymph nodes and the spleen.

  3. Are 3 - 4 times the size of red cells.

  4. Can change shape, move against the blood flow and squeeze through the walls of blood vessels into the surrounding tissue.

Platelets:

  1. Are tiny structures that do not have nuclei.

  2. Are formed from detached lining cells if blood vessels.

  3. Help to produce clotting when a blood vessel is damaged.

There is also a substance called fibrinogen in the blood. When bleeding occurs a chemical reaction changes fibrinogen into fibrin - thread like strands that help to form a clot.

Plasma:

  1. Is a pale, straw coloured, liquid.

  2. Is 92% water.

  3. 8% consists of food substances.

  4. Is the transportation system.

  5. Maintains the correct balance of chemicals, water content and temperature levels within the body.

The human body needs a constant supply of oxygen to enable energy to be released.

The respiratory system brings air (with oxygen) into the body via the lungs.

The respiratory system is made up of air passages, the lungs and the diaphragm.

When breathing in (inspiration):

  1. Muscles across the ribs contract and pull the ribs upwards.

  2. The muscles of the diaphragm also contract and flatten out the floor of the rib cage.

  3. The lungs increase in size and so suck in air through the nose and mouth.

When breathing out (expiration):

  1. Muscles of diaphragm and rib cage relax

  2. The diaphragm pushes back into a domed position by the organs beneath it under pressure from the muscular abdominal wall.

  3. The ribs move down under their own weight. The space the lungs occupy is now smaller and so air is forced out again.

The digestive system makes food soluble and able to pass into the bloodstream and be transported to the muscles and organs.

  1. In the mouth, where food is ground up by the teeth to form a pellet of food called a bolus.

  2. While in the mouth, an enzyme released from the salivary gland called ptyalin begins to turn starch into sugar.

  3. Food is pushed down the oesophagus (gullet) by a wave like action called peristalsis.

  4. When reaching the stomach, foods are mixed with gastric juices containing more enzymes and dilute hydrochloric acid.

  5. Food is released into the duodenum in small amounts with the relaxation of the pyloric sphincter. It spends approximately 6 hours here.

  6. Food is further digested by the action of a large number of alkaline enzymes. They break down food into a mixture of simple amino acids, fatty acids and glycerol.

  7. Undigested waste food passes into the colon (the large intestine) where it remains for 12 hours while more nutrients and water are absorbed into the bloodstream.

  8. The solid remains pass through the last part of the system where they leave the body through the anus.

  9. Waste fluids are taken to the kidneys. Here they are filtered off and pass as urine through the ureters to the bladder.

  10. The urine is expelled from the body through the urethra.

For muscles to contract, energy is required.

This energy can only be provided by the breakdown of a chemical called Adenosine Triphosphate (ATP):

During this reaction, energy is released and two new chemicals are formed: Adenosine Diphosphate (ADP) and a phosphate (P).

There is a limited quantity of ATP in the muscle cells.

For muscle contraction to continue ATP has to be re-built from ADP and P:

ADP + P = ATP

This re-building of ATP is known as Muscle Respiration.

There are two pathways by which ATP can be reformed:

The Anaerobic Pathway

The Aerobic Pathway

Anaerobic is without oxygen.

This means there is no oxygen present when ATP is reformed.

There are two methods of Anaerobic Respiration:

  1. The Alactic or Creatine Phosphate (CP) System.

    There is another chemical present in the muscle cell called Creatine Phosphate (CP).

    When there is a demand, due to muscle contraction, for ATP to be re-built CP breaks down, giving up its P to add to ADP to form ATP + C.

    ADP + CP = ATP + C.

    Like ADP, the cell has a limited quantity of CP in it, so this method of muscle respiration can only be used when short bursts of energy are required such as in shot-putt or sprint starting.

    If further muscle contractions are required then another method of muscle respiration is necessary.

  2. The Lactic Acid System.

    Present in all cells of the body is a food substance called glycogen, which is made from glucose obtained from digested food.

    When glycogen breaks down in the cell, it releases energy. This energy is then used to re-build ATP from ADP and P.

    ADP + P + glycogen = ATP + pyruvic acid

    As the lactic acid system is anaerobic, there is no oxygen present. Pyruvic acid without the presence of oxygen forms lactic acid.

    It is the build-up of lactic acid in the muscle that causes pain, discomfort and fatigue.

    Consequently, this method of muscle respiration can only be used for events lasting short periods of time, from between two to two and a half minutes.

    Examples of this are the longer sprints or the final part of longer events.

    For longer events, the body muscles must work with oxygen present, that is, aerobically.

Aerobic is with oxygen.

This pathway begins like the lactic acid system.

ADP + P + glycogen = ATP + pyruvic acid

However, because oxygen is present pyruvic acid is not converted into lactic acid but goes on to form another 34 molecules of ATP.

34 ADP + lactic acid + oxygen + 34 P = 34 ATP + water + carbon dioxide

Short term effects:

Heart rate increases rapidly providing the muscles with the necessary oxygen and nutrients to provide the muscles with energy.

During exercise, cardiac output is increased and stroke volume increases because:

  1. More blood is sent back to the heart due to the muscles squeezing blood in the veins.

  2. As the heart fills up, it stretches.

  3. As the muscle fibres stretch, they contract more strongly, pumping out more blood.

Long term effects:

The heart muscle will grow and strengthen becoming more efficient in heart rate and stroke volume.

Stroke volume is the amount of blood leaving each ventricle on each beat.

Short term effects:

Respiration increases to provide that oxygen and remove carbon dioxide.

This is done by:

  1. Increasing breathing rate by about three times the normal rate

  2. Increasing tidal volume by five times the normal rate

  3. Increasing blood supply to and through the lungs

  4. Increasing oxygen up take.

Tidal Volume is the amount of air taken in or out with each breath.

Long term effects:

The body becomes more efficient at using oxygen with an improvement in VO2 max a significant indicator of an athlete's physical fitness that can be accurately tested.

Blood is diverted to the heart, lungs and working muscles, away from parts of the digestive system.

Short term effects:

During intense exercise the body's temperature rises. Sweat is formed by sweat glands under the skin to help cool the body through evaporation.

Blood is diverted to the capillaries just below the skin. This causes the skin to redden.

Long term effects:

Exercise improves the general health and well being of the body.

It is kept toned and helps to prevent heart disease in later life.

It provides positive mental and social contributions to a person's life as well as positive physical contributions.