Contraction of diaphragm:

What keeps the lungs inflated even during expiration?

1. The smooth muscles of the lung

2. The diaphragm and the intercostal muscles alone

3. The visceral pleurae and the changing volume of the lungs

4. Surface tension from pleural fluid and negative pressure in the pleural cavity

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

(1) there is a negative pressure in the lungs

(2) there is a negative intrapleural pressure pulling at the lung walls

(3) there is a positive intrapleural pressure

(4) pressure in the lungs in higher than the atmospheric pressure

Hiccups can be best described as

(1) forceful sudden expiration

(2) forceful contraction of intercostal muscles during deep breathing

(3) vibration of the soft palate during breathing while sleeping

(4) jerky incomplete inspiration.

Assertion             :       Coughing and sneezing are necessary.

Reason                :      Coughing and sneezing are reflex actions.