Question

inspiration begins as ____________.multiple choicethe diaphragm relaxesthe diaphragm contractsthe lungs expandthe lungs contractthe external and internal intercostals contract

Explanation:

During inspiration (inhalation), the diaphragm contracts. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. This decrease in pressure within the thoracic cavity (compared to the atmospheric pressure) causes air to flow into the lungs. The relaxation of the diaphragm (option 1) is part of expiration (exhalation). The lungs expand (option 3) as a result of the diaphragm contracting (and external intercostal muscles contracting, but internal intercostals relax during normal inspiration - option 5 is incorrect as internal intercostals don't contract in normal inspiration). The lungs contracting (option 4) is part of expiration.

Answer:

the diaphragm contracts