what are the muscles of which contraction causes inspiration/ inhalation ?
The correct answer and explanation is:
Correct Answer: The diaphragm and external intercostal muscles are the primary muscles whose contraction causes inspiration (inhalation).
Explanation:
Inspiration, also known as inhalation, is the process of drawing air into the lungs. This process depends on the contraction of specific muscles that increase the volume of the thoracic cavity, which in turn decreases the pressure inside the lungs, allowing air to flow in.
The diaphragm is the main muscle involved in inspiration. It is a dome-shaped muscle located at the base of the lungs, separating the thoracic cavity from the abdominal cavity. During inspiration, the diaphragm contracts and moves downward. This movement increases the vertical dimension of the thoracic cavity, allowing the lungs to expand.
Along with the diaphragm, the external intercostal muscles also play an important role. These muscles are located between the ribs. When they contract, they pull the ribs upward and outward. This action expands the chest in both the anterior-posterior and lateral dimensions. The expansion further increases thoracic volume and reduces the internal pressure, promoting airflow into the lungs.
Other muscles may assist in deeper or forceful inhalation, including the sternocleidomastoid and scalene muscles in the neck. These accessory muscles elevate the sternum and the upper ribs, contributing to further expansion of the thoracic cavity. However, during quiet or normal breathing, only the diaphragm and external intercostal muscles are actively involved.
The process of inspiration is governed by the negative pressure principle: when the pressure inside the thoracic cavity falls below atmospheric pressure, air rushes in through the nose or mouth into the lungs. The nervous system, particularly the phrenic nerve, controls diaphragm contraction. Proper functioning of these muscles is essential for effective breathing and oxygen exchange.