Respiratory system

• Explain two reasons severe asthma attacks can cause a reduction in blood oxygen levels.

  • Contraction of bronchiole muscles will reduce the diameter of the bronchioles (1) and restrict airflow into the alveoli (1).

  • Secretion of excess mucus will reduce airflow into the alveoli (1) which will result in reduced gas exchange with the blood (1). • Reduced airflow to the alveoli (1) will reduce the surface area available for gas exchange (1). • Reduced gas exchange with the blood (1) will result in less oxygen entering the blood and therefore oxygen levels fall (1).
• One type of medication used in inhalers are muscle relaxants. Suggest how this medication can stop an asthma attack.


  • The muscle relaxant / inhaler causes the muscles of the bronchioles to relax (1) which increases airflow (to the alveoli) (1). • The bronchiole muscles relax after use of the inhaler (1) and airflow to the alveoli increases the surface area for gas exchange (1). • The relaxant medication allows airflow to the alveoli to increase the surface area for gas exchange (1) which allows more oxygen to enter the blood (1)