When we inhale, our diaphragm contracts. When we exhale our diaphragm relaxes.
The concept is simple and easy to memorize. But when you walk into your exam on test day, sit down, open the exam and read the first multiple choice question regarding the above situation, will you remember that the diaphragm contracts during an inhalation?
This scenario exemplifies the importance of learning a concept rather than memorizing. When learning a concept start with the pictures in your textbook. The authors include these pictures not to make the book look pretty or interesting to read, but rather to help you learn important concepts. These pictures and diagrams are just as important as the text, so take the time to read and understand figures.
|Photo Credit: Theresa Knott, picture modified by Science Matters|
The above figure will help you learn how the diaphragm muscle works to allow for negative pressure breathing. The diaphragm is a muscle located at the base of the ribs. When the diaphragm contracts, the muscle shortens. As you can see in the figure, when the diaphragm shortens, it flattens out, and this causes the rib cage to expand. As the rib cage expands, the lungs increase in volume. As the volume increases, the air pressure falls to below the atmospheric pressure. Since air flows from a region of high pressure to low pressure, air enters the lungs and you inhale.
The same picture can be used to understand exhalation. During exhalation, the diaphragm relaxes. The muscle elongates and the rib cage becomes smaller causing the lungs to decrease in size. Since the volume of the lungs is now less than what is was previously, the air pressure inside the lungs increases and becomes greater than the atmospheric pressure. Since air flows from a region of high pressure to a region of low pressure, air exits the lungs and you exhale.
Now that you have learned and understand the concept of negative pressure breathing, you are in a much better position to tackle that multiple choice question. And the best part? You are now prepared to answer a whole host of multiple choice questions as well as an essay question on negative pressure breathing.