Test: Mechanism of Breathing (August 3) - NEET MCQ

Spirometry is the process of recording the changes in the volume and movement of air in and out of the lungs and the instrument used for this purpose is called a spirometer or respirometer.

Fig: Spirometer

• A spirometer is a device used to measure the volume of air exchanged during breathing. It is commonly used in respiratory physiology to assess lung function. Spirometry is a non-invasive test that measures the amount and speed of air that can be inhaled and exhaled, providing information about lung capacity and airflow rates.
• Option A, Sphygmomanometer, is not a correct answer as it is a device used to measure blood pressure, not air volume during breathing movements.
• Option C, Hygrometer, is not a correct answer as it is a device used to measure humidity or moisture content in the air, not air volume during breathing movements.
• Option D, Stethoscope, is not a correct answer as it is a device used to listen to sounds produced by the body, such as heart and lung sounds, but it does not measure air volume during breathing movements.

The respiratory quotient (RQ) is the ratio of CO₂ produced to O₂ consumed while food is being metabolized.

RQ = CO_{2 eliminated}/O_2 consumed

• Respiratory quotient (RQ) is a term used in physiology to describe the ratio of the volume of carbon dioxide (CO₂) evolved to the volume of oxygen (O₂) consumed during respiration. It is used to determine the type of fuel (carbohydrates, fats, or proteins) being used by an organism for energy production.
• Option A, volume of CO₂ evolved - volume of O₂ consumed, is not a correct answer as it does not represent the ratio of CO₂ evolved to O₂ consumed.
• Option B, Volume of O₂ consumed/Volume of CO₂ evolved, is not a correct answer as it represents the reciprocal of the actual respiratory quotient, and therefore is not the correct definition of RQ.
• Option D, Volume of O₂ evolved/Volume of CO₂ consumed, is not a correct answer as it represents the reciprocal of the actual respiratory quotient, and therefore is not the correct definition of RQ.

Therefore, the correct answer is C: Volume of CO₂ evolved/Volume of O₂ consumed, which represents the actual definition of respiratory quotient, a ratio of CO₂ evolved to O₂ consumed during respiration.

Vital capacity is a measure of the maximum volume of air that can be forcefully exhaled after taking the deepest possible breath. It is the sum of three lung volumes: inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV),  (IRV + TV + ERV). 

• Inspiratory reserve volume (IRV) is the maximum volume of air that can be forcefully inhaled after a normal tidal inspiration.
• Tidal volume (TV) is the volume of air that is inhaled or exhaled during a normal breath.
• Expiratory reserve volume (ERV) is the maximum volume of air that can be forcefully exhaled after a normal tidal expiration.

So, the vital capacity is the sum of these three lung volumes: IRV + TV + ERV.

Option D is the correct answer as it includes all three components of vital capacity. Option A, B, and C do not include all three components and hence are not correct.

• Dead space air in humans refers to the volume of air that enters the respiratory system but does not participate in gas exchange with the blood. This is because it does not reach the alveoli, which are the tiny air sacs in the lungs where oxygen and carbon dioxide exchange occurs.
• The dead space air in humans is estimated to be around 150 ml. This means that when we inhale, about 150 ml of the air we breathe in does not contribute to the exchange of oxygen and carbon dioxide in the lungs, and instead remains in the upper respiratory tract (such as the trachea and bronchi) where it does not participate in gas exchange.

It's important to note that dead space air can vary depending on factors such as age, lung health, and breathing patterns.

• 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

• During inspiration, the diaphragm and external intercostal muscles contract, causing the rib cage to expand and move outward and expanding the thoracic cavity and lung volume.
• During expiration, the diaphragm and intercostals relax, causing the thorax and lungs to recoil.

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

Mammalian erythrocytes have short life span because they are enucleate cells i.e. cells do not have nucleus.