Test: Mechanism of Breathing (NCERT) - NEET MCQ

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.
Hence the correct Answer is "A"

The volume of air inspired or expired during normal breath is called tidal volume. It is about 500mL of air in average young adult man.

Vital capacity is the maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration.This equals the inspiratory reserve volume (IRV) + expiratory reserve volume (ERV) + tidal volume (TV). Its value is 3400 mL - 4800 mL.

During expiration, the internal intercostal muscles contract, and the diaphragm relaxes. This is because the internal intercostal muscles contracting and the diaphragm relaxing decreases the volume of the thoracic cavity. This in turn decreases the volume of the lungs. 

Inspiration is an active process while expiration is a passive process.

The correct sequence of events in the initiation of respiration is:
(i) The contraction of external intercostal muscles raises the ribs and sternum
(ii) The volume of thorax increases in the dorsoventral axis
(iv) Diaphragm contraction
(vi) The volume of thorax increases in the anterior-posterior axis
(iii) Intrapulmonary pressure decreases
(v) Air rushes into lungs
So, the correct answer is '(i), (ii), (iv), (vi), (iii), (v)'.

he correct answer is Option A : (D), (A), (C), (B), (E).

Here's the reasoning behind this order :

(D) Pulmonary ventilation by which atmospheric air is drawn in and CO₂ rich alveolar air is released out.

Respiration begins with pulmonary ventilation (breathing), which allows the atmospheric air to enter the lungs and CO₂-rich air to be exhaled.

(A) Diffusion of gases (O₂ and CO₂) across the alveolar membrane.

Inside the lungs, oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli across the alveolar membrane.

(C) Transport of gases by the blood.

Once in the bloodstream, oxygen and carbon dioxide are transported to and from the body's tissues.

(B) Diffusion of O₂ and CO₂ between blood and tissues.

Oxygen diffuses from the blood into the body's tissues, and carbon dioxide diffuses from the tissues into the blood.

(E) Utilisation of O₂ by the cells for catabolic reactions and resultant release of CO₂.

Finally, oxygen is used by cells for metabolic processes, creating carbon dioxide as a byproduct.

Therefore, the sequence is (D), (A), (C), (B), (E).

The correct option is : Option C

At higher altitudes, the air pressure is lower than at sea level. This means there is less atmospheric pressure to push oxygen into the lungs, which can make it more difficult for the body to get the oxygen it needs. This condition can lead to altitude sickness, which can cause symptoms such as difficulty breathing and heart palpitations, among others. This is the basis for the statement (A) and the reason given in statement (R) accurately explains this situation.

The correct fill-ups for the respective blank numbers are:
1. (1)-350
2. (2)-dead space air
3. (3)-vital capacity
4. (4)-4000 mL
5. (5)-500
6. (6)-tidal

The vital capacity (VC) of the lung is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV).

nspiratory reserve volume (IRV) is the amount of air that can be inhaled beyond a normal breath.

Expiratory reserve volume (ERV) is the amount of air that can be exhaled beyond a normal breath.

Tidal volume (TV) is the amount of air that is inhaled and exhaled during a normal breath.

Therefore, vital capacity (VC) = IRV + ERV + TV.

Option (c) is the correct answer as pneumotaxic centre is present in the pons region of the brain, that can moderate the functions of the respiratory rhythm centre.

Option (b) is incorrect as medulla oblongata possesses respiratory rhythm centre and a chemosensitive area.

Option (a) and (d) are incorrect as cerebrum and thalamus does not possess any specialised centre to moderate the respiratory rhythm to suit the demands of the body tissues.

Option (d) is the correct answer because statements (a), (c) and (e) are correct.

Vital capacity includes ERV, TV and IRV.

Vital capacity is the maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration.

Statement (b) is incorrect as total volume of air a person can inspire after a normal expiration is termed as inspiratory capacity (IC).

Statement (d) is incorrect as ERV, RV, IRV and TV comprise total lung capacity.

Inspiratory reserve volume (IRV) + tidal volume (TV) + expiratory reserve volume (ERV) represents vital capacity (VC). Now, inspiratory capacity is the total volume of ai that can be inhaled after a normal expiration. It includes tidal volume and inspiratory reserve volume i.e., IC = TV + IRV. Thus, option (a) is correct which says that vital capacity i.e., IRV + TV + ERV = IC + ERV.

Option (b) is the correct answer because every 100 ml of oxygenated blood can deliver around 5 ml of O₂ to the tissues under normal physiological conditions.

Option (c), (d) and (a) are incorrect because every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.