Test: Breathing Mechanism - NEET MCQ

Explanation: Inspiration is an active process in which muscle contraction do take place. At the time of inspiration, contraction in diaphragm and external intercostal muscles takes place.

• The maximum volume of air that a person can breathe in after forced expiration or the maximum volume of air that a person can breathe out after forced inspiration is called vital capacity. The value of vital capacity varies from 3400 mL to 4800 mL. 
• On the other hand, tidal volume is the air inspired or expired during normal breathing.
• Total lung capacity is the volume of air present in the lungs and respiratory passage after a maximum inspiration.
• Whereas, inspiratory capacity is the total volume of air that a person can inspire after a normal inspiration.

Hence, the correct answer is option B: Vital Capacity

Respiration in humans is the process of exchanging gases, specifically oxygen (O2) and carbon dioxide (CO2), between the body and the environment. It can be divided into three main steps: pulmonary ventilation, external respiration, and internal respiration.

• Pulmonary ventilation (option B) refers to the process of breathing, which involves the movement of air in and out of the lungs through inhalation (taking in air) and exhalation (expelling air).
• External respiration (options C and D) involves the exchange of gases between the lungs and the blood, as well as the transportation of oxygen and carbon dioxide in the blood. This includes the transport of gases by blood (option C) and the alveolar diffusion of oxygen and carbon dioxide (option D), which occurs in the alveoli, the small air sacs in the lungs where gas exchange occurs.
• Internal respiration (option A) refers to the process by which cells in the body utilize oxygen and produce carbon dioxide as part of cellular metabolism. However, the utilization of carbon dioxide by cells for catabolic (breakdown) reactions is not considered a step in the process of respiration. Instead, carbon dioxide produced during cellular metabolism is transported back to the lungs through the blood and then exhaled during exhalation.

So, the correct answer is A, as it is not a step in respiration but rather a utilization of a product of respiration by cells for other cellular processes

• Tidal volume refers to the amount of air that is normally inspired or expired with each breath during normal, quiet breathing. In other words, it is the volume of air that moves in and out of the lungs with each breath we take when we are at rest and not exerting ourselves.
  Tidal volume is an important parameter used to measure lung function and is typically measured in milliliters (ml). The average tidal volume for an adult at rest is around 500 ml, although it can vary depending on factors such as age, lung health, and physical activity level.
• Vital capacity (option A) is the maximum amount of air that can be forcibly exhaled after taking the deepest possible breath. 
• Residual volume (option B) is the volume of air that remains in the lungs even after maximum exhalation. 
• Normal volume (option C) is not a specific term used in the context of lung function or respiration.

So, the correct answer is D: Tidal volume, which refers to the amount of air that is normally inspired or expired with each breath during quiet breathing.

• Tidal volume is approximately 500ml while residual volume is 1100-1200 ml.
• Residual volume refers to the volume of air that remains in the lungs even after a maximum exhalation, meaning it is the amount of air that cannot be forcibly exhaled. It is important for maintaining the structure of the lungs and preventing them from collapsing.
• Tidal volume, on the other hand, is the amount of air that is normally inspired or expired with each breath during quiet breathing. It is the volume of air that moves in and out of the lungs with each breath during normal, resting breathing.

So, residual volume (option B) is greater than tidal volume, as it represents the volume of air that remains in the lungs after a normal tidal expiration

Larynx is a cartilaginous box which helps in sound production and hence called the sound box

Inspiration can occur if the pressure within the lungs is less than the atmospheric pressure.
So, there is a negative pressure in the lungs than the atmospheric pressure.

The pneumotaxic center, located in the pons region of the brain, can regulate the activity of the respiratory rhythm center.

During inspiration, the increase in thoracic volume leads to an increase in pulmonary volume. This increase in pulmonary volume results in a decrease in intra-pulmonary pressure, causing the atmospheric pressure to force air from the outside into the lungs. This process is crucial for breathing and the exchange of gases in the respiratory system.

During expiration, the thoracic cavity volume does not increase; it actually decreases.

When the diaphragm and intercostal muscles relax, the size of the thoracic cavity reduces. This decrease in volume leads to an increase in intra-pulmonary pressure, which then forces air out of the lungs. Therefore, an increase in thoracic cavity volume during expiration would be incorrect