Respiration – Mechanism of Breathing its regulation in humans: NEET MCQs with Answers

13 free questions on Respiration – Mechanism of Breathing its regulation in humans for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Mechanism of Breathing its regulation in humans

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Question 1

Previous-year question
Name the region of the human brain containing the pneumotaxic centre, which changes the respiratory rate by shortening the duration of inspiration. [Re-NEET 2022]
  1. Medulla
  2. Pons
  3. Thalamus
  4. Cerebrum
Show answer
Answer: (B) Pons
Explanation: The pneumotaxic centre is located in the pons region of the brain; its neural signals reduce the duration of inspiration and thereby alter the respiratory rate. The respiratory rhythm centre and the chemosensitive area are in the medulla, not the pneumotaxic centre.

Question 2

Previous-year question
Choose the correct statement. [NEET (Odisha) 2019]
  1. Expiration occurs due to external intercostal muscles
  2. Intrapulmonary pressure is lower than the atmospheric pressure during inspiration
  3. Inspiration occurs when atmospheric pressure is less than intrapulmonary pressure
  4. Expiration is initiated due to contraction of diaphragm
Show answer
Answer: (B) Intrapulmonary pressure is lower than the atmospheric pressure during inspiration
Explanation: During inspiration, contraction of the diaphragm and external intercostal muscles increases thoracic and pulmonary volume, so intrapulmonary pressure falls below atmospheric pressure and air rushes in. Inspiration needs atmospheric pressure greater than intrapulmonary pressure; expiration results from relaxation (not contraction) of the diaphragm and external intercostals.

Question 3

Previous-year question
Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort? [AIPMT 2011]
  1. One can breathe out air totally without oxygen
  2. One can breathe out air through the Eustachian tube by closing both nose and mouth
  3. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all
  4. The lungs can be made fully empty by forcefully breathing out all air from them
Show answer
Answer: (C) One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all
Explanation: Diaphragmatic (abdominal) breathing without rib movement is entirely possible with conscious effort. The others are impossible: expired air still contains about 15.7% oxygen (inspired air has 20.84%); the Eustachian tube merely equalises middle-ear pressure and cannot vent air; and the residual volume (about 1200–1500 mL) can never be expelled.

Question 4

Previous-year question
Lungs do not collapse between breaths, and some air always remains in the lungs which can never be expelled, because [NEET 2016, Phase II]
  1. there is a negative pressure in the lungs
  2. there is a negative intrapleural pressure pulling at the lung walls
  3. there is a positive intrapleural pressure
  4. pressure in the lungs is higher than the atmospheric pressure
Show answer
Answer: (B) there is a negative intrapleural pressure pulling at the lung walls
Explanation: A negative intrapleural pressure continuously pulls outward on the lung walls and keeps the alveoli distended. This is helped by the surfactant (DPPC) secreted by the cells of the outer alveolar wall, which lowers surface tension and prevents alveolar collapse. Hence a residual volume of air always remains.

Question 5

Previous-year question
Select the correct statement. [NEET (Odisha) 2019]
  1. Expiration occurs due to the external intercostal muscles
  2. Intrapulmonary pressure is lower than the atmospheric pressure during inspiration
  3. Inspiration occurs when atmospheric pressure is less than intrapulmonary pressure
  4. Expiration is initiated due to contraction of the diaphragm
Show answer
Answer: (B) Intrapulmonary pressure is lower than the atmospheric pressure during inspiration
Explanation: Air moves down a pressure gradient, so inspiration requires the intrapulmonary pressure to fall below atmospheric pressure. The other options invert the facts: expiration follows relaxation (not contraction) of the diaphragm and external intercostals, and inspiration occurs when atmospheric pressure exceeds intrapulmonary pressure.

Question 6

Previous-year question
Select the correct statements that occur during inspiration. I. Contraction of the diaphragm. II. Contraction of the external inter-costal muscles. III. Pulmonary volume decreases. IV. Intrapulmonary pressure increases. [NEET (Sep.) 2020]
  1. III and IV
  2. I, II and IV
  3. Only IV
  4. I and II
Show answer
Answer: (D) I and II
Explanation: Statements I and II are correct: contraction of the diaphragm pulls it downward while the external intercostal muscles lift the ribs and sternum, both of which enlarge the thoracic cavity. Statements III and IV are wrong — pulmonary volume increases and intrapulmonary pressure falls below atmospheric pressure, which is what draws air into the lungs.

Question 7

Previous-year question
Intercostal muscles occur in the [2004]
  1. ribs
  2. abdomen
  3. diaphragm
  4. thigh
Show answer
Answer: (A) ribs
Explanation: The intercostal muscles lie in the spaces between successive ribs. The external intercostals raise the ribs and sternum during inspiration, increasing the anteroposterior diameter of the thorax, while the internal intercostals pull them down during forced expiration.
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Question 8

Previous-year question
Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because [AIPMT (Phase-2), 2016]
  1. Pressure in the lungs is higher than the atmospheric pressure.
  2. There is a negative pressure in the lungs.
  3. There is a negative intrapleural pressure pulling at the lung walls.
  4. There is a positive intrapleural pressure.
Show answer
Answer: (C) There is a negative intrapleural pressure pulling at the lung walls.
Explanation: A negative (sub-atmospheric) intrapleural pressure continuously pulls on the lung walls, keeping the lungs partly inflated so they never fully collapse.

Question 9

Previous-year question
Which one of the following is a possibility for most of us in regards to breathing, by making a conscious effort? [AIPMT (Mains.), 2011]
  1. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs.
  2. The lungs can be made fully empty by forcefully breathing out all air from them.
  3. One can breathe out air totally without oxygen.
  4. One can breathe out air through Eustachian tubes by closing both the nose and the mouth.
Show answer
Answer: (A) One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs.
Explanation: With conscious effort one can breathe by moving only the diaphragm (abdominal breathing) without moving the ribs. The lungs can never be fully emptied because residual volume remains, expired air always contains oxygen, and air cannot be breathed out through the Eustachian tubes.

Question 10

During the pause between two quiet breaths, no air is moving in or out of the lungs. Which statement about the intra-pulmonary pressure at this moment is correct?
  1. It is higher than atmospheric pressure, because the diaphragm stays contracted
  2. It equals atmospheric pressure, so there is no pressure gradient to move air
  3. It is lower than atmospheric pressure, as it is during inspiration
  4. It is higher than atmospheric pressure, as it is during expiration
Show answer
Answer: (B) It equals atmospheric pressure, so there is no pressure gradient to move air
Explanation: Air moves only along a pressure gradient between the lungs and the atmosphere. Inspiration needs intra-pulmonary pressure below atmospheric pressure, and expiration needs it above. When no air is moving, the two pressures are equal.

Question 11

A chest wound lets outside air enter the space between the chest wall and one lung. The diaphragm on that side still contracts, yet the lung fails to inflate. The best explanation is that
  1. contraction of the diaphragm forces air out of the lung instead of drawing it in
  2. the alveoli of that lung lose their ability to exchange oxygen as soon as they meet outside air
  3. lungs cannot change their volume directly, and pulmonary volume follows the volume of an air-tight thoracic chamber
  4. lungs expand by their own muscle fibres, and these are paralysed by the entry of air
Show answer
Answer: (C) lungs cannot change their volume directly, and pulmonary volume follows the volume of an air-tight thoracic chamber
Explanation: The lungs have no muscle of their own to change their volume. The thoracic chamber is air-tight, so an increase in its volume is passed on to the lungs and lowers intrapulmonary pressure. When air enters the chamber, this link is lost, and contraction of the diaphragm no longer expands that lung.

Question 12

Arrange these events of normal inspiration in the correct order. A: Intra-pulmonary pressure falls below atmospheric pressure. B: Diaphragm and external intercostal muscles contract. C: Air moves from outside into the lungs. D: Volume of the thoracic chamber increases. E: Pulmonary volume increases.
  1. B, D, E, A, C
  2. B, A, D, E, C
  3. D, B, E, C, A
  4. B, E, D, C, A
Show answer
Answer: (A) B, D, E, A, C
Explanation: Contraction of the diaphragm and external intercostals enlarges the thoracic chamber. This enlargement is passed on to the lungs, so pulmonary volume increases. The larger volume lowers intra-pulmonary pressure below atmospheric pressure, and air then flows in along this gradient.

Question 13

Which description correctly gives the state of the diaphragm and the intra-pulmonary pressure at the moment a quiet expiration has just ended and the next inspiration has not yet begun?
  1. Diaphragm relaxed and dome-shaped; intra-pulmonary pressure above atmospheric pressure
  2. Diaphragm relaxed and dome-shaped; intra-pulmonary pressure equal to atmospheric pressure
  3. Diaphragm contracted and flattened; intra-pulmonary pressure below atmospheric pressure
  4. Diaphragm contracted and flattened; intra-pulmonary pressure equal to atmospheric pressure
Show answer
Answer: (B) Diaphragm relaxed and dome-shaped; intra-pulmonary pressure equal to atmospheric pressure
Explanation: Relaxation of the diaphragm during expiration returns it to its dome shape. Intra-pulmonary pressure rises above atmospheric only while air is being pushed out. Once expiration ends there is no pressure gradient, so the pressure equals atmospheric pressure and airflow stops.

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