NEET Biology: Mechanism of breathing and its regulation in humans Practice Questions
15 free multiple-choice questions on Mechanism of breathing and its regulation in humans (Human Physiology) for NEET Biology, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. Which of the following is the primary stimulus that drives the respiratory rate during exercise, especially when oxygen levels drop?
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Correct answer: D — Increase in the level of oxygen in the blood
During exercise, the increased metabolic activity leads to the production of large amounts of carbon dioxide and lactic acid. While increased CO2 stimulates respiration, the primary trigger that drives the increased *rate* of breathing (hyperpnea) to meet oxygen demands is the drop in arterial oxygen levels (hypoxia) detected by peripheral chemoreceptors.
Q2. Which muscle is primarily responsible for the active process of inhalation (breathing in)?
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Correct answer: D — Diaphragm
The diaphragm is the principal muscle of respiration. When the diaphragm contracts and moves downward, it increases the volume of the thoracic cavity, causing air to flow into the lungs (inhalation).
Q3. Which muscle plays the most significant role in the process of inhalation (inspiration) during normal breathing?
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Correct answer: A — Diaphragm
The diaphragm is the principal muscle of respiration. When it contracts and flattens, it moves downward, increasing the vertical dimension of the thoracic cavity, which draws air into the lungs, making it the most crucial muscle for inhalation.
Q4. According to Boyle's Law, what happens to the volume of the lungs when the internal pressure increases?
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Correct answer: A — Volume decreases
Boyle's Law states that pressure and volume are inversely proportional. When pressure inside the lungs increases, the volume of the lungs decreases (as air is pushed out).
Q5. The change in air pressure within the respiratory tract is directly related to the change in which physical property?
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Correct answer: C — Volume of the thoracic cavity
Air flows from an area of higher pressure to an area of lower pressure. The change in air pressure inside the lungs depends directly on the volume change of the chest cavity.
Q6. During normal quiet breathing, what happens to the volume of the thoracic cavity?
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Correct answer: A — It increases
In normal breathing, the increase in thoracic volume during inhalation is balanced by the decrease during exhalation, resulting in a net fluctuation around the resting volume.
Q7. The primary mechanical event that drives air movement into the alveoli is a change in atmospheric pressure compared to the pressure inside the lungs. This pressure difference is known as:
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Correct answer: B — Pressure gradient
Air moves from an area of higher pressure to an area of lower pressure. This difference in pressure between the atmosphere and the lungs creates the pressure gradient necessary for breathing.
Q8. Which part of the respiratory system is primarily responsible for the exchange of oxygen and carbon dioxide with the blood?
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Correct answer: A — Alveoli
The alveoli are tiny air sacs where the actual diffusion of gases (oxygen into the blood and carbon dioxide out of the blood) occurs.
Q9. Which structure primarily facilitates the movement of air into and out of the lungs?
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Correct answer: D — Lungs
While the lungs contain the alveoli for exchange, the overall movement of air (ventilation) occurs through the entire respiratory tract, including the trachea and the spaces within the lungs, driven by changes in thoracic volume.
Q10. The main function of the respiratory system is to facilitate the exchange of gases. What is the primary gas that enters the blood from the atmosphere during inhalation?
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Correct answer: D — Oxygen
Inhalation involves the intake of air, which is rich in oxygen (O₂), from the atmosphere. This oxygen diffuses across the alveolar membrane into the bloodstream.
Q11. Which part of the brainstem is primarily responsible for regulating the basic rhythm of breathing?
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Correct answer: C — Medulla oblongata
The respiratory centers are located in the medulla oblongata and pons of the brainstem. These centers maintain the involuntary, rhythmic control over breathing.
Q12. During normal expiration (breathing out) at rest, which muscular action is primarily involved?
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Correct answer: D — Relaxation of the diaphragm and external intercostal muscles
Resting expiration is largely a passive process where the diaphragm and external intercostal muscles relax, allowing the elastic recoil of the lungs and chest cavity to push air out.
Q13. Which set of chemoreceptors primarily monitors the level of carbon dioxide and pH in the blood to regulate the rate and depth of breathing during normal physiological conditions?
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Correct answer: B — Central chemoreceptors in the medulla oblongata
The central chemoreceptors, located in the medulla oblongata, are the most important regulators. They monitor the pH and CO₂ concentration in the cerebrospinal fluid, providing the primary signal to the respiratory control centers to adjust breathing rate and depth.
Q14. Which of the following structures is primarily responsible for the bulk of the movement during inhalation in humans?
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Correct answer: D — Diaphragm
The diaphragm is the principal muscle of respiration. During inhalation, the diaphragm contracts and flattens, moving downwards, which increases the volume of the thoracic cavity and causes air to enter the lungs.
Q15. The stimulus that mainly triggers the urge to breathe rapidly when blood CO₂ levels rise in the blood is the increase in:
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Correct answer: B — Carbon dioxide concentration
Increased concentration of carbon dioxide (CO₂) in the blood leads to an increase in acidity (lower pH), which is the main chemical trigger for the respiratory centers to increase the rate and depth of breathing.
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