Inspiration occurs when intrapulmonary pressure is,
a)lower than atm pressure
b)zero compared to atm pressure
Inspiration occurs when intrapulmonary pressure is lower than atm pressure
During inspiration, the volume of the thoracic cavity increases, causing intrapulmonary pressure to fall below atmospheric pressure. This is also known as a negative pressure. Since air moves from areas of high to low air pressure, air flows into the lungs. Notice that at the end of inspiration, when the intrapulmonary pressure again equals atmospheric pressure, airflow stops.