Biology Questions and Answers – Mechanism of Breathing-1

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Breathing-1”.

1. Which instrument is used for measuring volume of air involved in breathing?
a) Spirometer
b) Galvanometer
c) Aerometer
d) Electrocardiogram
View Answer

Answer: a
Explanation: The volume of air involved in breathing movements can be estimated by using a spirometer which helps in clinical assessment of pulmonary functions. It measures the amount of air inspired or expired by an individual.
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2. Which of the following is passive process?
a) Inspiration
b) Normal expiration
c) Forceful inspiration
d) Forceful expiration
View Answer

Answer: b
Explanation: Normal expiration is a passive process as during expiration, contraction (in any muscle) does not take place. Thus, there is no expenditure of energy. Relaxation in diaphgram and external intercoastal muscles is found.

3. At the time of inspiration, _________ takes place.
a) relaxation in external intercostal muscle
b) relaxation in diaphragm
c) contraction in diaphragm
d) no effect on diaphragm
View Answer

Answer: c
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.
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4. Inspiration occurs when there is ___________
a) no pressure gradient
b) negative pressure in the lungs
c) positive pressure in the lungs
d) more pressure in lungs than atmosphere
View Answer

Answer: b
Explanation: 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.

5. The amount of air inspired or expired during normal breathing is_________ ml.
a) 500
b) 500-1000
c) 1000-1100
d) 2100
View Answer

Answer: a
Explanation: Tidal volume is the amount of air inspired or expired during normal breathing. Its value for man is 500ml, out of which 150ml is dead space volume which remains in the respiratory tract.
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6. Which muscles can help in increasing the strength of breathing?
a) Arm muscle
b) Chest muscles
c) Abdominal muscles
d) Facial muscle
View Answer

Answer: c
Explanation: We have the ability to increase the strength of inspiration and expiration with the help of additional muscles called abdominal muscles. This is called as forceful breathing.

7. Vital capacity = ________
a) ERV + RV
b) IRV + TV
c) IRV + TV + ERV + RV
d) IRV + ERV + TV
View Answer

Answer: d
Explanation: Vital capacity is the amount of air that can be expired by most forceful expiration after a deepest inspiration. Inspiratory reserve volume, expiratory reserve volume and tidal volume are included in it.
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8. Which one of the following changes takes place during inspiration?
a) Decrease in thoracic cavity
b) Relaxation in diaphragm
c) Relaxation in external intercostal muscles
d) Sternum moves towards ventral and anterior direction
View Answer

Answer: d
Explanation: During inspiration, thoracic volume increases. Sternum moves towards ventral and anterior direction, diaphragm contracts, ribs move towards outside and ventral side.

9. Decrease in thoracic volume is marked by________
a) diaphragm relaxed
b) diaphragm contracted
c) sternum moving towards ventral and anterior direction
d) ribs moving out
View Answer

Answer: a
Explanation: Decrease in thoracic volume is necessary for expiration and is marked by relaxation in diaphragm and external intercostal muscle. Decrease in thoracic volume is necessary in order to build more pressure than atmospheric pressure.
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10. Time taken in breathing _______
a) inspiration 2 sec and expiration 3 sec
b) inspiration 3 sec and expiration 3 sec
c) inspiration 2 sec and expiration 2 sec
d) inspiration 3 sec and expiration 2 sec
View Answer

Answer: a
Explanation: Inspiration takes about 2 second and expiration takes about 3 second in normal condition and process. On an average an adult human breathes for about 16 times in a minute.

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