NCERT Exemplar MCQs

Hint

(a) Respiration in insects is independent of its coelomic fluid. They respire by a tracheal system and the cells exchange \(O_{2} / C O_{2}\) directly with the air in the tubes.

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(c) Diffusion of gases is a physical phenomenon that takes place between the tissue and blood vessels and does not occur during breathing whereas bringing air to the body temperature, its cleaning and warming occurs during the process of breathing.

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(d) The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere. The pressure within the lungs is less than the atmospheric pressure so there is a negative pressure in the lungs with respect to atmospheric pressure.

The puncture in the chest affects this pressure gradient maintained by the lungs and thus may cause cessation of breathing.

Hint

(b) Haemoglobin consists of a protein globin and pigment here. The four portions of iron in name combine with molecules of oxygen. It is an easy reversible reaction to form oxyhaemoglobin
\(
\mathrm{Hb}+\mathrm{O}_{2} \rightleftharpoons \mathrm{HbO}_{2}
\)
Whereas, the complex formed by the reaction of carbon monooxide and haemoglobin is incredibly strong
\(
\underset{\text { (Haemoglobin) }}{\mathrm{Hb}+\mathrm{CO}} \longrightarrow \underset{\begin{array}{c}
\text { (Carboxy } \\
\text { haemoglobin) }
\end{array}}{\mathrm{HbCO}}
\)
As a result of this strong between the haemoglobin and carbon monoxide the haemoglobin loses its affinity to oxygen thus may lead to choking or even death.

Hint

(b) Inspiration is the process by which fresh atmospheric air enters into the alveoli of the lungs, it is an active process and is brought about by the activity of inspiratory muscles. Expiration is the process by which foul air is expelled out of the lungs. Expiration is a normal passive process that involves the relaxation of inspiratory muscles.

Hint

(c) The maximum volume of air that a person can breathe in after forced expiration or the maximum volume of air that a person can breathe out after forced inspiration is called vital capacity

\(
\begin{array}{ccc}
\mathrm{VC}=\mathrm{IRV} & +\mathrm{ERV} & +\mathrm{TV} \\
\text { (Inspiratory reserve volume) } & \text { (Expiratory reserve volume) } & \text { (Tidal volume) }
\end{array}
\)
The value of vital capacity varies from \(3400 \mathrm{~mL}\) to \(4800 \mathrm{~mL}\).
On the other hand, tidal volume is the air inspired or expired during normal breathing. Total lung capacity is the volume of air present in the lungs and respiratory passage after maximum inspiration. Whereas, inspiratory capacity is the total volume of air that a person can inspire after normal inspiration.

Hint

(a) Factors that affect the oxygen hemoglobin binding by increasing its affinity are:
(i) Increased partial pressure of oxygen
(ii) decreases partial pressure of carbon dioxide.
(iii) High hydrogen ion concentration leading to low \(\mathrm{pH}\)
(iv) Low temperature
So, the correct option is ‘Higher \(\mathrm{pH}^{\text {‘. }}\).

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(a) Each terminal bronchiole gives rise to a network of bronchi.
Bronchi to bronchiole:
The bronchi are subdivided into small bronchioles which enter in the lungs and terminate into the small bag-like structure alveoli. 

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(b) Emphysema is. a condition of short breath due to breakdown of the alveolar wall and reduction of the respiratory area due to smoking.

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(b) Pneumotaxic Centre Located in the dorsal part of pons varolii of the brain can reduce the duration of inspiration and thus alter the respiratory rate. It is called the switch-off point of breathing since it is known to limit the duration of inspiration. This center influences the respiratory rhythm center by regulating the breathing rate.

Apneustic Centre Whereas is located in the lower part of pons varoli is responsible for promoting inspiration process.

Chemosensitive Centre is situated adjacent to the rhythm centre which is highly sensitive to \(\mathrm{CO}_{2}\) and hydrogen ions. Increase in \(\mathrm{CO}_{2}\) and \(\mathrm{H}^{+}\)in body and activates this centre for the elimiration of \(\mathrm{CO}_{2}\) and \(\mathrm{H}\)

Medullary Inspiratory Centre is a specialised region present in the medulla of the brain. and is primarily responsible for regulating the respiratory rhythm.

Hint

(b) High \(\mathrm{PO}_{2}\) and low \(\mathrm{PCO}_{2}\) in the lung blood capillaries favours separation of \(\mathrm{CO}_{2}\) from carbaminohaemoglobin.
When, the \(\mathrm{pCO}_{2}\) is low and \(\mathrm{pO}_{2}\) is high as in the lung alveoli, dissociation of \(\mathrm{CO}_{2}\) from carbamino-haemoglobin takes place, \(\mathrm{CO}_{2}\) which is bound to haemoglobin from the tissue is delivered at the alveoli, to maintain the concentration of \(\mathrm{CO}_{2}\) thus increasing \(\mathrm{pCO}_{2}\).Exchange of gases takes place between tissue capillary and tissue cells. Capillary cells with high \(\mathrm{pO}_{2}\) causes diffusion of \(\mathrm{O}_{2}\) into tissue cells via tissue fluid on the other hand high \(\mathrm{pCO}_{2}\) in the tissue cells causes diffusion of \(\mathrm{CO}_{2}\) into tissue capillary via tissue fluid.

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(d) Spirometry is the process of recording the changes in the volume and movement of air in and out of the lungs and the instrument used for this purpose is called spirometer or respirometer.

Stethoscope is a medical device used for listening to the internal sounds of an animal or human body.

Hygrometer is a device used for measuring the moisture content in the atmosphere, i.e., humidity.
Sphygmomanometer is a device that is used to measure blood pressure.

Hint

(b) (i) Inspiratory Capacity (IC)=Tidal Volume + Inspiratory Reserve Volume (TV + IRV).
(ii) Vital Capacity (VC) Tidal Volume \(+\) Inspiratory Reserve Volume \(+\) Expiratory Reserve Volume. (TV + ERV + IRV)
(iii) Residual Volume (RV) Volume of air remaining in the lungs after a forcible expiration.
(iv) Tidal Volume (TV) Volume of air inspired or expired during normal respiration.

Hint

(a) A sigmoid curve obtained when percentage saturation of haemogblobin with \(\mathrm{O}_{2}\) is plotted against the \(\mathrm{pO}_{2}\).

The oxygen haemoglobin dissociation curve is shifted to the right under the following condition.
(i) Decrease in partial pressure of oxygen.
(ii) Increase in partial pressure of carbon oxide.
(iii) Increase in hydrogen concentration.
(iv) Decrease in \(\mathrm{pH}\) activity.
(v) Increased body temperature.

Hint

(b) Earthworm respire through their moist cuticle and aquatic arthropods, respire through the trachea.
Fishes respire through gills, and birds/reptiles respire through lungs.