Human Biology 101: Respiratory System - Mechanics of Breathing, Inspiration, Expiration, Pressure Changes

Concept Summary

• Inspiration is the process by which air enters the lungs, resulting in an increase in lung volume.
• Expiration is the process by which air leaves the lungs, resulting in a decrease in lung volume.
• The diaphragm and intercostal muscles are the primary muscles responsible for inspiration.
• The pressure inside the lungs is lower than the atmospheric pressure during inspiration, causing air to enter the lungs.
• The pressure inside the lungs is higher than the atmospheric pressure during expiration, causing air to leave the lungs.

Questions

WHAT (definitional)

1. What is the primary function of the diaphragm during inspiration?
2. Answer: The diaphragm contracts and flattens, increasing the volume of the thoracic cavity.
3. Real-world example: When you inhale deeply, your diaphragm contracts and your belly expands.
4. Misconception cleared: The diaphragm does not move upwards during inspiration, but rather flattens and increases the volume of the thoracic cavity.
5. What is the role of the intercostal muscles during expiration?
6. Answer: The intercostal muscles contract and pull the ribs downwards, decreasing the volume of the thoracic cavity.
7. Real-world example: When you exhale deeply, your intercostal muscles contract and your chest sinks inwards.
8. Misconception cleared: The intercostal muscles do not relax during expiration, but rather contract to decrease the volume of the thoracic cavity.
9. What is the difference in pressure between the lungs and the atmosphere during inspiration?
10. Answer: The pressure inside the lungs is lower than the atmospheric pressure during inspiration.
11. Real-world example: When you inhale, the air pressure outside your body is greater than the air pressure inside your lungs, causing air to enter your lungs.
12. Misconception cleared: The pressure inside the lungs is not equal to the atmospheric pressure during inspiration, but rather lower, allowing air to enter the lungs.

WHY (causal reasoning)

1. Why does the diaphragm contract during inspiration?
2. Answer: The diaphragm contracts to increase the volume of the thoracic cavity, allowing air to enter the lungs.
3. Real-world example: When you inhale deeply, your diaphragm contracts to increase the volume of your lungs, allowing more oxygen to enter your body.
4. Misconception cleared: The diaphragm does not contract to push air out of the lungs, but rather to increase the volume of the thoracic cavity and allow air to enter the lungs.
5. Why does the pressure inside the lungs decrease during inspiration?
6. Answer: The pressure inside the lungs decreases during inspiration because the diaphragm contracts and the volume of the thoracic cavity increases.
7. Real-world example: When you inhale, the air pressure inside your lungs decreases, allowing air to enter your lungs.
8. Misconception cleared: The pressure inside the lungs does not increase during inspiration, but rather decreases, allowing air to enter the lungs.
9. Why does the pressure inside the lungs increase during expiration?
10. Answer: The pressure inside the lungs increases during expiration because the diaphragm relaxes and the volume of the thoracic cavity decreases.
11. Real-world example: When you exhale deeply, the air pressure inside your lungs increases, causing air to leave your lungs.
12. Misconception cleared: The pressure inside the lungs does not decrease during expiration, but rather increases, causing air to leave the lungs.

HOW (process/application)

1. How does the diaphragm contract during inspiration?
2. Answer: The diaphragm contracts by shortening and flattening, increasing the volume of the thoracic cavity.
3. Real-world example: When you inhale deeply, your diaphragm contracts and your belly expands.
4. Misconception cleared: The diaphragm does not move upwards during inspiration, but rather flattens and increases the volume of the thoracic cavity.
5. How does the intercostal muscle contract during expiration?
6. Answer: The intercostal muscle contracts by pulling the ribs downwards, decreasing the volume of the thoracic cavity.
7. Real-world example: When you exhale deeply, your intercostal muscles contract and your chest sinks inwards.
8. Misconception cleared: The intercostal muscles do not relax during expiration, but rather contract to decrease the volume of the thoracic cavity.
9. How does the pressure inside the lungs change during inspiration and expiration?
10. Answer: The pressure inside the lungs decreases during inspiration and increases during expiration.
11. Real-world example: When you inhale, the air pressure inside your lungs decreases, allowing air to enter your lungs. When you exhale, the air pressure inside your lungs increases, causing air to leave your lungs.
12. Misconception cleared: The pressure inside the lungs does not remain constant during inspiration and expiration, but rather changes to allow air to enter or leave the lungs.

CAN (possibility/conditions)

1. Can the diaphragm contract during expiration?
2. Answer: No, the diaphragm relaxes during expiration.
3. Real-world example: When you exhale deeply, your diaphragm relaxes and your belly sinks inwards.
4. Misconception cleared: The diaphragm does not contract during expiration, but rather relaxes to decrease the volume of the thoracic cavity.
5. Can the intercostal muscles relax during inspiration?
6. Answer: No, the intercostal muscles contract during inspiration.
7. Real-world example: When you inhale deeply, your intercostal muscles contract and your chest expands.
8. Misconception cleared: The intercostal muscles do not relax during inspiration, but rather contract to increase the volume of the thoracic cavity.
9. Can the pressure inside the lungs remain constant during inspiration and expiration?
10. Answer: No, the pressure inside the lungs changes during inspiration and expiration.
11. Real-world example: When you inhale, the air pressure inside your lungs decreases, allowing air to enter your lungs. When you exhale, the air pressure inside your lungs increases, causing air to leave your lungs.
12. Misconception cleared: The pressure inside the lungs does not remain constant during inspiration and expiration, but rather changes to allow air to enter or leave the lungs.

TRUE/FALSE (misconception testing)

1. The diaphragm contracts during expiration.
2. Answer: FALSE
3. Real-world example: When you exhale deeply, your diaphragm relaxes and your belly sinks inwards.
4. Misconception cleared: The diaphragm does not contract during expiration, but rather relaxes to decrease the volume of the thoracic cavity.
5. The intercostal muscles relax during inspiration.
6. Answer: FALSE
7. Real-world example: When you inhale deeply, your intercostal muscles contract and your chest expands.
8. Misconception cleared: The intercostal muscles do not relax during inspiration, but rather contract to increase the volume of the thoracic cavity.
9. The pressure inside the lungs remains constant during inspiration and expiration.
10. Answer: FALSE
11. Real-world example: When you inhale, the air pressure inside your lungs decreases, allowing air to enter your lungs. When you exhale, the air pressure inside your lungs increases, causing air to leave your lungs.
12. Misconception cleared: The pressure inside the lungs does not remain constant during inspiration and expiration, but rather changes to allow air to enter or leave the lungs.