Tag: breathing and exchange of gas

Questions Related to breathing and exchange of gas

Percentage of O$ _2$ present in inhaled air in man is about 

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. 21%

  2. 78%

  3. 1%

  4. 43%

Show answer
Correct Option: A
Explanation:

Inhaled air contains more oxygen used to create energy and less carbon dioxide. Exhaled air which contains more carbon dioxide produced as a waste product of energy production and less oxygen as it has been used in respiration. Inhaled air contains 21% oxygen, 0.04% CO$ _2$ and 79% N$ _2$. Exhaled air contains 16% oxygen, 4% CO$ _2$ and 79% N$ _2$.

Therefore, the correct answer is option A.

During inspiration, the diaphragm

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Becomes dome-shaped

  2. Flattens

  3. Remains unchanged

  4. Rotates sidewise

Show answer
Correct Option: B
Explanation:

The diaphragm is located below the lungs and is the major muscle of respiration. It is large, dome-shaped muscle that contracts rhythmically and continually. upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its dome-like shape, and is forced out of the lungs.
Therefore, the correct answer is option B.

In man, expired air contains oxygen about 

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. 4%

  2. 10%

  3. 16%

  4. 20%

Show answer
Correct Option: C
Explanation:

Inhaled air contains more oxygen used to create energy and less carbon dioxide. Exhaled air which contains more carbon dioxide produced as a waste product of energy production and less oxygen as it has been used in respiration. Inhaled air contains 21% oxygen, 0.04% CO$ _2$ and 79% N$ _2$. Exhaled air contains 16% oxygen, 4% CO$ _2$ and 79% N$ _2$. 

Therefore, the correct answer is option C.

The volume of thoracic cavity increases during

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Never

  2. Expiration

  3. Both A and B

  4. Inspiration

Show answer
Correct Option: D
Explanation:

Increase in volume of thoracic cavity is seen in case of inspiration. Inspiration results in flattened diaphragm. The volume of thoracic cavity decreases during expiration and the diaphragm relaxes and comes to its original dome shape. 

Therefore, the correct answer is option D.

Fill in the blanks:


Component              Inspired air             Expired air
Oxygen                            a                         16.4%
Nitrogen                        79%                        b

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. a = 5.6%, b = 21.6%

  2. a = 20.96%, b = 79.6%

  3. a = 28.8, b = 98%

  4. a = 1%, b = 2%

Show answer
Correct Option: B
Explanation:

Component       Inspired air     Expired air

Oxygen                  20.96%            16.4%
Carbon dioxide       0.04%              4%
Nitrogen                   79%               79.6%

During forced expiration, actively contracting muscles include the

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Diaphragm

  2. External intercostals

  3. Abdominal muscles

  4. Diaphragm and intestinal muscle

Show answer
Correct Option: C
Explanation:

The most important muscles of forced expiration are those of the abdominals. When these muscles contract, intra-abdominal pressure is raised, and the diaphragm is pushed upward. These muscles also contract forcefully during coughing, vomiting, and defecation. The internal intercostal muscles assist active expiration by pulling the ribs downward and inward thus decreasing the thoracic volume. 

The exchange of gases in the alveoli of the lungs takes place by

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Osmosis

  2. Simple diffusion

  3. Passive transport

  4. Active transport

Show answer
Correct Option: B
Explanation:
Passive or simple diffusion is the movement of solutes (gas or ions) from an area of high concentration to an area of low concentration. Gases diffuse across the systemic capillary membrane and the cell membranes of the target tissue. Carbon dioxide diffuses from systemic tissues to lungs, and oxygen diffuses from lungs to systemic tissues
So, the correct answer is 'Simple diffusion'

Which of the following activity does not take place during pulmonary respiration?

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Movement of buccal cavity

  2. Contraction and relaxation of sternohyal and pterohyal muscles

  3. Successive opening and closing of mouth and external nostrils

  4. All of the above

  5. No activity takes place

Show answer
Correct Option: C
Explanation:
Successive opening and closing of mouth and external nostrils do not take place during pulmonary respiration.
The mechanism of pulmonary respiration: It includes breathing movement, exchange of gases, in lungs, transport of gases by blood and exchange of gases by tissue. 
The medulla oblongata (with the inspiratory centre and expiratory centre) and pons varolli (with pneumotoxic centre) are the breathing centre that regulates the breathing mechanism. Inspiratory centre stimulates inspiratory muscle (diaphragm) to control the rhythm of respiration. Expiratory centre remains inactive during normal breathing but it controls both expiration and inspiration during exercise. Pneumotoxic centre controls the switch off point of the breathing sending signal to inspiratory centre. The medulla’s control centre detects low pH of tissue fluid during formation of more carbonic acids, the centre increases the rate of breathing to eleiminate the excess CO2. The concentration of O2 has little effect on breathing centers. However, when O2 level is severely depressed, O2 sensors in the aorta and carotid arteries send signals to breathing control center to increase the breathing rate.
The main purpose of the respiratory system is to provide oxygen to the tissues and to remove carbon dioxide from them. This entire process is achieved through the following steps:
  • Breathing or pulmonary ventilation leading to exchange of oxygen and carbon dioxide between the atmospheric air and the lungs
  • Exchange of gases at the alveolar surface
  • Transport and exchange of gases in the tissues
  • Cellular respiration


The O$ _2$ in the exhaled air is

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. About 8%

  2. About 10%

  3. About 15%

  4. About 20%

Show answer
Correct Option: C
Explanation:

In respiration, the human body exhales about 15% of the oxygen that is not utilized by the body. 

In human beings, rib case and sternum move upwardly and outwardly during.

zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

  1. Exercise

  2. Sudden back injury

  3. Expiration

  4. Inspiration

Show answer
Correct Option: D