Question

Asthma sufferers experience attacks during which it is very difficult for them to draw air into the lungs (inspire). Which of the following could cause these symptoms?

A A change that increases the pressure differential between the atmospheric air and the air in the alveoli.

B Contraction of the smooth muscles of the bronchioles.

C Reduction of blood flow through the pulmonary capillaries.

D Increased cardiac output.

Answer 1

Ans:-

B,

Contraction of the smooth muscles of the bronchioles , is the cause of very difficulty for the ashtma sufferers to draw air into the lungs because during an asthma attack , the muscles that surrounds the bronchial tubes constrict , narrowing the air passages and making it very difficult to breathe .

Rest of given options are wrong because:-

- A change that increases the pressure differential between the atmospheric air and the air in the alveoli initiates respiration not ashtma.

- There is no role of reduction of blood flow throug the pulmonary capillaries in asthma attack because due to asthma attack blood flow reduces but reduced blood flow doesn't cause asthma attack.

- during asthma attack cardiac output increases but increased cardiac output doesn't cause asthma attack.