Biology

Respiration and Gas Exchange

989 Questions

Access a targeted set of questions on respiration and gas exchange for competitive exams. Topics include lung volumes, the mechanism of breathing, and respiratory anatomy. Understanding these physiological processes is essential for scoring well.

Lung volumes and capacitiesBreathing mechanismsRespiratory anatomyGas exchange processes

Respiration and Gas Exchange Questions

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

When diaphragm of man is completely dome shaped it shows

  1. End of expiration and beginning of inspiration

  2. Beginning of expiration and end of inspiration

  3. Increased rate of breathing

  4. Decreased rate of breathing
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continuously, and most of the time, involuntarily. 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 air is forced out of the lungs. Diaphragm contracts, moves down and flattens during inhalation and diaphragm relaxes and curves upwards during exhalation. So, when diaphragm of man is completely dome shaped, it shows that beginning of expiration and end of inspiration. Thus, option B is correct. 

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

Inspiration takes place during

  1. Inhalation

  2. Exhalation

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Inhalation (also known as inspiration) is the flow of air into an organism. It is a vital process for all human life. In humans it is the movement of air from the external environment, through the airways, and into the alveoli. Inhalation begins with the contraction of the muscles attached to the rib cage. This causes an expansion in the chest cavity. Then takes place the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's Law. This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. Air enters, inflating the lung through either the nose or the mouth into the pharynx (throat) and trachea before entering the alveoli. 

Therefore, the correct answer is option A.

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

During inspiration, the diaphragm

  1. Becomes dome-shaped

  2. Flattens

  3. Remains unchanged

  4. Rotates sidewise
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

The volume of thoracic cavity increases during

  1. Never

  2. Expiration

  3. Both A and B

  4. Inspiration
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

During forced expiration, actively contracting muscles include the

  1. Diaphragm

  2. External intercostals

  3. Abdominal muscles

  4. Diaphragm and intestinal muscle
Reveal answer Fill a bubble to check yourself
C Correct answer
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. 

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

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

  1. Osmosis

  2. Simple diffusion

  3. Passive transport

  4. Active transport
Reveal answer Fill a bubble to check yourself
B Correct answer
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'
Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

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

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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


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

During inspiration.

  1. Diaphragm and external intercostal muscles relax

  2. Diaphragm and internal intercostal muscles relax

  3. Diaphragm and external intercostal muscles contract

  4. Diaphragm and internal intercostal muscles contract
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Inspiration is an active process involving the contraction of the diaphragm (moving downward) and the external intercostal muscles (lifting the ribs).

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

Which is correct?

  1. During inspiration, external intercostal muscles and diaphragm contract

  2. Cyanosis means collapse of alveoli

  3. Eupnoea is slow breathing

  4. Coryza is caused by human corona virus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Option A correctly describes the active phase of breathing. The other options are incorrect: cyanosis is a bluish discoloration due to low oxygen, eupnoea is normal breathing, and coryza is typically caused by rhinoviruses.

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

Read the following statements regarding mechanism of respiration and choose the correct option.
$1$. Inspiration occurs only when there is negative pressure in the lungs with respect to atmosphere
$2$. Expiration takes place only when intrapulmonary pressure is lower than atmospheric pressure
$3$. Pressure gradients are generated with the help of diaphragm and intercostal muscles
$4$. Inspiration is initiated by relaxation of diaphragm
$5$. Contraction of diaphragm reduces pulmonary volume and increases intrapulmonary pressure causing expiration.

  1. $1, 2$ and $5$ correct
  2. $2$ only correct
  3. $2, 5$ correct
  4. $1, 3$ correct
  5. $1, 4$ correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1 is correct (negative pressure is required). Statement 3 is correct (muscles create the pressure gradient). Statements 2, 4, and 5 are incorrect because expiration is passive (relaxation) and contraction of the diaphragm increases volume, not reduces it.

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

With conscious efforts one can.

  1. Breathe out air totally without oxygen

  2. Breathe in and out by moving diaphragm alone without moving ribs at all

  3. Breathe out air through eustachian tube by closing both nose and mouth

  4. Empty the lungs completely by breathing out all air out of them
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The diaphragm and intercostal muscles are skeletal muscles, allowing for some conscious control. One can choose to breathe using only the diaphragm (abdominal breathing) or only the ribs (thoracic breathing).

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

Which of the following is the most appropriate in normal circumstances?

  1. During inspiration the intrapulmonary pressure is less than the atmospheric pressure

  2. During expiration the intrapulmonary pressure is less than the atmospheric pressure

  3. During inspiration the intrapulmonary pressure is more than the atmospheric pressure

  4. During expiration the intrapulmonary pressure is equal to atmospheric pressure
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For air to flow into the lungs during inspiration, the intrapulmonary pressure must be lower than the atmospheric pressure, creating a pressure gradient.