NEET Zoology Breathing and Exchange of Gases Questions Solved

NEET - 2015

When you hold your breath which of the following gas changes in blood would first lead to the urge to breathe?

(1) Falling O2 concentration

(2) Rising CO2 concentration

(3) Falling CO2 concentration

(4) Rising CO2 and falling O2 concentration

(2)When you hold your breath the ongoing accumulation of carbon dioxide in your cells, in your blood and lungs will eventually irritate and trigger impulses from the respiratory center part of your brain. Rising levels of carbon dioxide signal the body to breathe and ensure our unconscious and autonomous respiration. 

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NEET - 2017

Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of

(a) Residual Volume (RV)

(b) Inspiratory Reserve Volume (IRV)

(c) Tidal Volume (TV)

(d) Expiratory Reserve Volume (ERV)

Audio Explanation:


(a) In lungs, even after the most forceful expiration, some of the volume of air remains. This volume is termed Residual Volume (RV). Due to this, lungs do not collapse even after the most forceful expiration. RV is about 1100 mL to 1200 mL.

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NEET - 2016

The partial pressure of oxygen in the alveoli of the lungs is  

(a) equal to that in the blood

(b) more than that in the blood

(c) less than that in the blood

(d) less than that of carbon dioxide

Audio Explanation:


(b) The partial pressure of oxygen (pO2) in alveoli of lungs is 104 mm Hg, which is more than that of blood in the blood capillaries of lung alveoli (40 mm Hg) This difference allows passive diffusion of O2 from air filled in the lungs to the blood vessels of lung alveoli.

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NEET - 2016

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

(a) there is a negative pressure in the lungs

(b) there is a negative intrapleural pressure pulling at the lung walls

(c) there is a positive intrapleural pressure

(d) pressure in the lungs in higher than the atmospheric pressure

(b) Lungs do not collapse between breaths and some air always remains in the lungs which can be never expelled because there is a negative intrapleural pressure pulling at the lung walls. Alveoli are basic functional unit of lungs. The outer alveolar wall surface has cells which secrete DPPC also called as lipid surfactant. The surfactant expands the alveoli due to which the negative pressure inside the alveoli increases. This prevents the alveoli from collapsing. Since, in this question both options (a) and (b) are correct and option (b) provides more appropriate explanation, therefore, it must be chosen.

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NEET - 2016

Reduction in pH of blood will

(a) reduce the blood supply to the brain

(b) decrease the affinity of hemoglobin with oxygen

(c) release bicarbonate ions by the liver

(d) reduce the rate of heart beat

(b) Reduction in pH of blood i.e., increase in acidity favours the dissociation of oxyhemoglobin thereby giving upmore O2. When this phenomenon occurs due to increase in CO2 concentration then it is called Bohr effect.

 

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NEET - 2016

Name the chronic respiratory disorder caused mainly by cigarette smoking

(a) asthma

(b) respiratofy acidosis

(c) respiratory alkalosis

(d) emphysema

Audio Explanation:


(d) Emphysema is characterised by inflation or distension of alveoli by dissolution of wall of the two adjacent lung alveoli. It generally occurs due to chronic cigarette smoking.

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NEET - 2015

Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls.

(a) Pleurisy

(b) Pneumonia

(c) Emphysema

(d) Asthma

Audio Explanation:


(c) Empysema is a chronic respiratory disease where there is over-inflation of the air sacs (alveoli) in the lung, causing a decrease in lung function and often, breathlessness. In this disease, the alveolar walls are damaged leading to drastic reduction in gas exchange.

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NEET - 2014

Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs

(a) as bicarbonate ions

(b) in the form of dissolved gas molecules

(c) by binding to RBC

(d) as carbamino-haemoglobin

Audio Explanation:


Because of its high solubility, about 7% of carbon dioxide gets dissolved in the blood plasma and is carried to the wings in the same way. The largest fraction of carbon dioxide, i.e, (about 70%) is converted to bicarbonates (HCO3) and transported in the plasma.

CO2 + H2anhydrasecarbonicH2CO3 anhydrasecarbonic HCO3- + H+

About (-23% of CO2 is carried by haemoglobin as carbominohaemoglobin

CO2 + Hb (haemoglobin) HbCO3 (carboamino haemoglobin)

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NEET - 2013

The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D. Select the option, which gives correct identification and main function and/or characteristic.


(a) A-trachea-long tube supported by complete cartilaginous rings for conducting inspired air

(b) 8-pleural membrane-surround ribs on both sides to provide cushion against rubbing

(c) C-alveoli-thin walled vascular bag-like structures for exchange of gases

(d) D-lower end of lungs-diaphragm pulls it down during inspiration

(c) C-Alveoli are thin-walled vascular bag-like structures for exchange of gases. ,4-trachea or wind pipe is an air conducting tube through, which transport of gases takes place. 8-pleural membrane is double layered, which reduces friction on the lunc surface. D-diaphragm is involved in the inspiration and expiration process of breathing.

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NEET - 2012

Which one of the following is the correct statement for respiration in humans?

(a) Cigarette smoking may lead to inflammation of bronchi

(b) Neural signals from pneumotoxic centre in pons region of brain can increase the duration of inspiration

(c) Workers in grinding and stone breaking industries may suffer, from lung fibrosis

(d) About 90% of carbon dioxide (CO2) is carried by haemoglobin as carbamino haemoglobin

Audio Explanation:


Irritating gases, fumes, dusts, etc., present in the work place result in lung disorders. Pneumoconiosis is a condition of permanent deposition of particulate matter in the lungs. Tissue reaction to these irritating substances causes proliferation of fibrous connective tissue called fibrosis. It is common in flour mill workers, iron mill workers, coalminers, stone grinders, etc. A strong pneumotoxic signal from pons varoli reduces the inspiration duration to only 0.5 second while weak signal may prolong the inspiration duration to five seconds.

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