Breathing and Exchange of Gases

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

1. Falling CO2 concentration
2. Rising CO2 and falling O2 concentration
3. Falling O2 concentration
4. Rising CO2 concentration

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

1. as bicarbonate ions
2. in the form of dissolved gas molecules
3. by binding to R.B.C.
4. as carbamino-haemoglobin.

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. [Figure]

1. A - Trachea - Long tube supported by complete cartilaginous rings for conducting inspired air.
2. C - Alveoli - Thin walled vascular bag like structures for exchange of gases.
3. B - Pleural membrane - Surround ribs on both sides to provide cushion against rubbing.
4. D - Lower end of lungs - Diaphragm pulls it down during inspiration.

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

1. Cigarette smoking may lead to inflammation of bronchi.
2. Neural signals from pneumotaxic centre in pons region of brain can increase the duration of inspiration.
3. Workers in grinding and stone-breaking industries may suffer from lung fibrosis.
4. About 90% of carbon dioxide (CO2) is carried by haemoglobin as carbamino-haemoglobin.

Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?

1. One can breathe out air totally without oxygen.
2. One can breathe out air through Eustachian tube by closing both nose and mouth.
3. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
4. The lungs can be made fully empty by forcefully breathing out all air from them.

Bulk of carbon dioxide (CO2) released from body tissues into the blood is present as

1. bicarbonate in blood plasma and RBCs
2. free CO2 in blood plasma
3. 70% carbamino-haemoglobin and 30% as bicarbonate
4. carbamino-haemoglobin in RBCs.

A large proportion of oxygen remains unused in the human blood even after its uptake by the body tissues. This O2

1. acts as a reserve during muscular exercise
2. raises the pCO2 of blood to 75 mm of Hg.
3. is enough to keep oxyhaemoglobin saturation at 96%
4. helps in releasing more O2 to the epithelial tissues.

The figure given below shows a small part of human lung where exchange of gases takes place. Select the option which represents labelled part (A, B, C or D) correctly identified along with its function. [Figure]

1. D : capillary wall - exchange of O2 and CO2 takes place here
2. B : red blood cells - transport of CO2 mainly.
3. A : alveolar cavity - main site of exchange of respiratory gases
4. C : arterial capillary - passes oxygen to tissues

Listed below are four respiratory capacities (i – iv) and four jumbled respiratory volumes of a normal human adult. array|l|l|l| & Respiratory capacities & Respiratory volumes \ (i) & Residual volume & 2500 mL \ (ii) & Vital capacity & 3500 mL \ (iii) & Inspiratory reserve volume & 1200 mL \ (iv) & Inspiratory capacity & 4500 mL \ array Which one of the following is the correct matching of two capacities and volumes?

1. (ii) 2500 mL, (iii) 4500 mL
2. (iii) 1200 mL, (iv) 2500 mL
3. (iv) 3500 mL, (i) 1200 mL
4. (i) 4500 mL, (ii) 3500 mL

What is true about RBCs in humans?

1. They carry about 20-25 percent of CO2.
2. They transport 99.5 percent of O2.
3. They transport about 80 percent oxygen only and the rest 20 percent of it is transported in dissolved state in blood plasma.
4. They do not carry CO2 at all.

Which two of the following changes (i – iv) usually tend to occur in the plain dwellers when they move to high altitudes (3,500 m or more)? (i) Increase in red blood cell size (ii) Increase in red blood cell production (iii) Increased breathing rate (iv) Increase in thrombocyte count Changes occurring are

1. (ii) and (iii)
2. (iii) and (iv)
3. (i) and (iv)
4. (i) and (ii)

What is vital capacity of our lungs?

1. Inspiratory reserve volume plus expiratory reserve volume
2. Total lung capacity minus residual volume
3. Inspiratory reserve volume plus tidal volume
4. Total lung capacity minus expiratory reserve volume

The haemoglobin of a human foetus

1. has only 2 protein subunits instead of 4
2. has a higher affinity for oxygen than that of an adult
3. has a lower affinity for oxygen than that of the adult
4. its affinity for oxygen is the same as that of an adult.

The majority of carbon dioxide produced by our body cells is transported to the lungs as

1. attached to haemoglobin
2. dissolved in the blood
3. bicarbonates
4. carbonates.

Which one of the following statements is incorrect?

1. The principle of countercurrent flow facilitates efficient respiration in gills of fishes.
2. The residual air in lungs slightly decreases the efficiency of respiration in mammals.
3. The presence of non-respiratory air sacs increases the efficiency of respiration in birds.
4. In insects, circulating body fluids serve to distribute oxygen to tissues.

People living at sea level have around 5 million RBC per cubic millimetre of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude

1. people eat more nutritive food, therefore more RBCs are formed
2. people get pollution-free air to breathe and more oxygen is available
3. atmospheric O2 level is less and hence more RBCs are needed to absorb the required amount of O2 to survive
4. there is more UV radiation which enhances RBC production.

Blood analysis of a patient reveals an unusually high quantity of carboxyhaemoglobin content. Which of the following conclusions is most likely to be correct? The patient has been inhaling polluted air containing unusually high content of

1. carbon disulphide
2. chloroform
3. carbon dioxide
4. carbon monoxide.

When CO2 concentration in blood increases breathing becomes

1. shallower and slow
2. there is no effect on breathing
3. slow and deep
4. faster and deeper

Given below are four matchings of an animal and its kind of respiratory organ: The correct matchings are

1. (A) and (B)
2. (A), (B) and (C)
3. (B) and (D)
4. (C) and (D).