The Need for Energy
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The Need for Energy. State the function of red blood cells and plasma, and explain the function of haemoglobin. State the function of the coronary artery. Describe blood flow around the body, and what makes a pulse. Describe gas exchange at the capillaries, and explain their efficiency.

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The Need for Energy

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The Need for Energy

State the function of red blood cells and plasma, and explain the function of haemoglobin

State the function of the coronary artery

Describe blood flow around the body, and what makes a pulse

Describe gas exchange at the capillaries, and explain their efficiency

State the function of the 4 chambers of the heart and the valves

Describe the path of blood flow through heart and blood vessels

Explain the difference in heart wall thickness

Describe the mechanism of breathing

Describe the features of the lungs which make them efficient gas exchange surfaces

Explain the function of cilia, cartilage and mucus in the lungs

State the effects of an imbalance of energy inputs/outputs

Describe the exchange of gases during breathing in the air sacs

Describe the internal structure of the lungs

Energy Needs

Everyone has different energy needs. Who needs the most energy in each of the following pairs?

1. Office worker or labourer?

2. Pregnant woman and woman who is not pregnant?

3. 14 year old and someone in their twenties?

Labourer – more active.

Pregnant woman – needs energy for her baby as well as herself.

14 year old – energy for growing.

We release energy from our food by respiration.

For respiration to occur efficiently, we need oxygen.

How does oxygen get into our blood?

How does oxygen get to every part of our body?

Breathe in, and passes into blood at lungs.


The air we breathe in has more oxygen, less carbon dioxide, and more dirt than the air we exhale.

The following link will take you to a diagram of the respiratory system.


When we breathe in, intercostal muscles contract, moving the ribs up and out. The diaphragm moves down. Both movements allow the lungs to expand, and draw in air.

The opposite is true when we breathe out.

The trachea and bronchi are strengthened by rings of cartilage to stop the passages closing.

  • Lungs

  • The lungs are large, pink, spongy organs. They are efficient at gas exchange because:

  • Large surface area (due to millions of alveoli)

  • Alveoli walls are thin – allowing rapid diffusion of O2 and CO2

  • Alveoli are moist so O2 and CO2 can dissolve for diffusion to take place

  • Millions of capillaries to provide good blood supply to alveoli.






The Passage of Oxygen

Oxygen enters mouth/nose

Carbon dioxide will pass in the opposite direction.

Lining of Air Passages

When we breathe in, germs and dirt in the air is trapped in the mucus lining our air passages. The mucus is then moved up to our mouth by the beating of cilia. The mucus is then swallowed. The stomach acid destroys all dirt and germs. The mucus is produced by goblet cells in the air passages.

The Heart

Once oxygen has entered the blood, it then needs to be carried to all body cells.

The heart pumps blood around the body.

The following link will take you to a diagram of the heart, which you can scroll through to see the circulation of blood.

Blood comes to back to the heart from the body in the venae cavae. Blood enters the right atrium. Blood is then pumped to the right ventricle, where it is pumped to the lungs in the pulmonary artery.

Blood travels back to the heart from the lungs in the pulmonary vein. It enters the left atrium. Blood is then pumped down to the left ventricle. From there it is pumped to the rest of the body in the aorta.

The heart is made of muscle.

The atria have thin walls, as they only pump blood a short distance (to ventricles). The ventricles have thicker walls, as they pump blood further (around body). The left ventricle is thicker than the right, as it has to pump blood around the whole body. The right ventricle only has to pump blood to the lungs.

The heart contains valves to stop blood flowing in the wrong direction. Semi-lunar valves are in the arteries to stop blood going back to the ventricles. The bicuspid valve stops blood going from the left ventricle to the left atrium, and the tricuspid valve stops blood going from the right ventricle to the right atrium.

Blood Vessels

Blood vessels allow blood to move around the body.


The only artery which does not carry oxygenated blood is the pulmonary artery, and the only vein which does not carry deoxygenated blood is the pulmonary vein.


Red blood cells contain haemoglobin. This pigment contains iron, which is what binds with oxygen.

Changing Levels

of Performance

Describe how training effects the breathing system

Describe how recovery time can indicate fitness and how it is affected by training

Describe what is meant by recovery time

State the cause of muscle fatigue, and in terms of the chemical change

Compare changes in pulse and breathing rates in trained and untrained people

Explain why pulse and breathing rate increase with exercise

Effects of Exercise

What happens to your body during exercise?

Why do these changes occur?

During exercise, muscles are continuously working, so need more oxygen for respiration to release energy. Due to this your pulse rate increases, meaning the heart is pumping more oxygenated blood, and the breathing rate increases to take in more oxygen.

Muscle Fatigue

Muscles become fatigued as they are continuously contracted. Fatigue is caused by insufficient oxygen.

In low levels of oxygen, muscles resort to anaerobic respiration.

Glucose Lactic acid + little energy

This process is less efficient than aerobic respiration.

It is the build up of lactic acid that causes muscle fatigue.

As you exercise, pulse and breathing rates increase, and lactic acid builds up. Recovery time is the time taken for all these factors to return to normal after exercise. The shorter the recovery time, the fitter the individual.

Pulse, and breathing rates increase less in an athlete, as lungs and heart become more efficient.

This means oxygen can be supplied to muscles faster, allowing lactic acid to be broken down faster. This is called paying back the oxygen debt. The quicker this is done, shorter the recovery time.

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