1. BREATHING

2. Breathing  During inhalation, air is sucked into the lungs as the chest cavity enlarges and air pressure inside the lungs fall below outside air pressure.

3. Breathing  During inhalation, air is sucked into the lungs as the chest cavity enlarges and air pressure inside the lungs fall below outside air pressure.  The diaphragm is the main muscle involved, but the shoulder and rib muscles also assist.

4. Breathing  During inhalation, air is sucked into the lungs as the chest cavity enlarges and air pressure inside the lungs fall below outside air pressure.  The diaphragm is the main muscle involved, but the shoulder and rib muscles also assist.  Exhalation is passive – the diaphragm and rib muscles relax, reducing the space inside the chest cavity, so air, now higher in pressure than air outside, is pushed out of the lungs and the lungs deflate.

5. Breathing  Breathing rate is controlled by the respiratory centre at the base of the brain.

6. Breathing  Breathing rate is controlled by the respiratory centre at the base of the brain.  Signals from this centre automatically contract the diaphragm and rib muscles to cause inhalation.

7. Breathing  Breathing rate is controlled by the respiratory centre at the base of the brain.  Signals from this centre automatically contract the diaphragm and rib muscles to cause inhalation.  These signals are triggered by the amount of carbon dioxide in the blood – the more CO 2 the faster the breathing rate.

8. Breathing  Breathing rate is controlled by the respiratory centre at the base of the brain.  Signals from this centre automatically contract the diaphragm and rib muscles to cause inhalation.  These signals are triggered by the amount of carbon dioxide in the blood – the more CO 2 the faster the breathing rate.  During normal relaxed breathing, about 500ml of air is inhaled per breath.

9. Breathing  A resting adult takes about 12 breaths per minute, making 12 x 500ml = 6L of air inhaled per minute.

10. Breathing  A resting adult takes about 12 breaths per minute, making 12 x 500ml = 6L of air inhaled per minute.  During strenuous exercise, breathing rate and volume of air taken in increase dramatically, and inhalation rates as high as 100L of air/minute are achieved.

11. Breathing  A resting adult takes about 12 breaths per minute, making 12 x 500ml = 6L of air inhaled per minute.  During strenuous exercise, breathing rate and volume of air taken in increase dramatically, and inhalation rates as high as 100L of air/minute are achieved.  During exercise, lactic acid accumulates in muscles – this build-up is known as oxygen debt.

12. Breathing  A resting adult takes about 12 breaths per minute, making 12 x 500ml = 6L of air inhaled per minute.  During strenuous exercise, breathing rate and volume of air taken in increase dramatically, and inhalation rates as high as 100L of air/minute are achieved.  During exercise, lactic acid accumulates in muscles – this build-up is known as oxygen debt.  Oxygen is needed to change the lactic acid back to glucose.

13. Breathing  A resting adult takes about 12 breaths per minute, making 12 x 500ml = 6L of air inhaled per minute.  During strenuous exercise, breathing rate and volume of air taken in increase dramatically, and inhalation rates as high as 100L of air/minute are achieved.  During exercise, lactic acid accumulates in muscles – this build-up is known as oxygen debt.  Oxygen is needed to change the lactic acid back to glucose.  Rapid breathing after exercise removes lactic acid.

14. Breathing  Breathing is not a very efficient process – only ¼ oxygen inhaled ends up in the pulmonary bloodstream because:

15. Breathing  Breathing is not a very efficient process – only ¼ oxygen inhaled ends up in the pulmonary bloodstream because: - 30% of the air that enters the lung is in ‘dead space’ in the bronchi or bronchioles

16. Breathing  Breathing is not a very efficient process – only ¼ oxygen inhaled ends up in the pulmonary bloodstream because: - 30% of the air that enters the lung is in ‘dead space’ in the bronchi or bronchioles - Oxygen must diffuse from the lung to the bloodstream, and diffusion is a relatively slow process. Only some inhaled oxygen has diffused into the bloodstream by the time exhalation occurs.