Mechanism of Breathing — NEET Biology MCQs with Solutions
Free NEET Biology Mechanism of Breathing MCQs with step-by-step solutions (6 questions). Part of Breathing and Exchange of Gases. Practise online on Prepizo — no login needed.
▶ Practise Mechanism of Breathing online (free)
Questions with solutions
Q1 — Mechanism of Breathing · easy · theory
Inspiration (breathing in) occurs when the pressure inside the lungs (intra-pulmonary pressure) becomes:
A. Equal to atmospheric pressure
B. Less than atmospheric pressure ✓ Correct
C. Greater than atmospheric pressure
D. Zero
Solution: A drop in intrapulmonary pressure below atmospheric draws air into the lungs (inspiration).
Q2 — Mechanism of Breathing · easy · theory
During inspiration, the diaphragm ______ and the external intercostal muscles ______:
A. Relaxes; contract
B. Contracts (flattens); contract ✓ Correct
C. Contracts; relax
D. Relaxes; relax
Solution: Contraction of the diaphragm and external intercostals increases thoracic volume, lowering pressure for inspiration.
Q3 — Mechanism of Breathing · medium · theory
Expiration is normally a ______ process because:
A. Active; the diaphragm flattens
B. Passive; the lungs pump air
C. Passive; the diaphragm and intercostals relax, reducing thoracic volume ✓ Correct
D. Active; muscles contract forcefully
Solution: Quiet expiration is passive — muscle relaxation reduces thoracic/pulmonary volume, raising pressure to expel air.
Q4 — Mechanism of Breathing · medium · theory
The contraction of the external intercostal muscles raises the ribs and sternum, increasing the ______ of the thoracic chamber:
A. Vertical axis only
B. Antero-posterior (front-to-back) diameter ✓ Correct
C. Pleural fluid
D. Volume of the abdomen
Solution: External intercostals lift the ribs/sternum, increasing the antero-posterior dimension of the thorax.
Q5 — Mechanism of Breathing · hard · theory
The respiratory rhythm centre that controls breathing is located in the:
A. Hypothalamus
B. Medulla oblongata ✓ Correct
C. Cerebellum
D. Cerebrum
Solution: The medulla houses the respiratory rhythm centre; a pneumotaxic centre in the pons can moderate it.
Q6 — Mechanism of Breathing · hard · theory
A rise in CO₂ and H⁺ concentration in the blood is sensed by chemosensitive areas that then:
A. Have no effect
B. Stop breathing
C. Decrease the breathing rate
D. Signal the rhythm centre to increase the rate and depth of breathing ✓ Correct
Solution: CO₂/H⁺ (not O₂ primarily) are the main regulators; their rise stimulates faster, deeper breathing to expel CO₂.