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Chapter 5

Respiratory System

Class 6 - Concise Biology Selina


Multiple Choice Questions

Question 1

In humans, taking air through nostril into the nasal cavity is called

  1. Inhalation
  2. Exhalation
  3. Cellular respiration
  4. Internal respiration

Answer

Inhalation

Reason — Inhalation is the physical process by which the air containing oxygen is drawn into the our lungs through nostrils into the nasal cavity.

Question 2

The front opening of the wind pipe is guarded by

  1. Glottis
  2. Exoglottis
  3. Epiglottis
  4. Trachea

Answer

Epiglottis

Reason — The epiglottis is a muscular flap shaped in the throat. It closes the wind pipe at the time of swallowing of food.

Question 3

The process during which food is oxidised and energy is released is called

  1. Cellular respiration
  2. Excretion
  3. Digestion
  4. Transpiration

Answer

Cellular respiration

Reason — Cellular respiration is the process of oxidation of glucose (breaking down of food) in the cells with the release of energy in the form of ATP molecules (Adenosine triphosphate).

Short Answer Questions

Question 1(i)

Why do our body cells require oxygen?

Answer

Our body cells require oxygen for the break down of glucose and release energy for carrying out various activities of the body.

Question 1(ii)

What is the difference between breathing and respiration?

Answer

Difference between Breathing and Respiration:

BreathingRespiration
Breathing is a physical process.Respiration is a bio-chemical process.
Air containing oxygen is taken into the lungs and air loaded with carbon dioxide is given out.Oxygen taken in is used in oxidizing glucose and energy is released.
Lungs are mainly involved.Occurs in all living cells of the body.

Question 1(iii)

Name the by-products formed during the oxidation of food.

Answer

Carbon dioxide and Water is released as by-products during the oxidation of food.

Question 1(iv)

Name the agent which transports oxygen to all parts of the body.

Answer

Blood with help of haemoglobin in RBCs transports oxygen to all parts of the body.

Question 1(v)

What is the role of epiglottis during swallowing?

Answer

Epiglottis closes the wind pipe at the time of swallowing the food.

Question 2

Describe in brief the function of ribs and diaphragm in breathing.

Answer

The function of Ribs and Diaphragm is to aid respiration:

  1. Ribs — In breathing during inhalation, the Ribs move upwards and outward. This function increases the volume of chest cavity. As a result lungs expand and atmospheric air rushes into the lungs. During Exhalation, the Ribs move downwards and inward. This function decreases the volume of chest cavity as a result lungs contract and air rushes out of the lungs.
  2. Diaphragm — During inhalation, Diaphragm is pushed downwards and it becomes flattened while during exhalation, it moves upwards and becomes dome-shaped.

Question 3

Name the gas which is expelled out during expiration. Where is it originally produced in our body?

Answer

Carbon dioxide is the gas which is expelled during expiration. It is produced in the cells of the body.

Question 4

Name the following.

(i) Respiratory process in which oxygen is not utilized.

(ii) Respiratory process in which oxygen is utilized.

(iii) The microscopic air-sac of the lungs.

(iv) The two membranes which protect the lungs.

Answer

(i) Anaerobic Respiration.

(ii) Aerobic Respiration.

(iii) Alveoli.

(iv) Outer and inner pleura.

Long Answer Questions

Question 1

Why is a respiratory system necessary?

Answer

Respiration is a vital process in all living organisms.

Respiratory system is necessary because:

  1. Respiration is a vital process in all living organisms. Every cell of a plant, an animal or of human body requires energy for various activities. Respiratory system provides this energy by the oxidation of glucose using oxygen.
  2. Respiratory system helps in breathing through which oxygen from the air is pulled into the lungs and the air containing carbon dioxide is forced out of the lungs.
  3. Respiratory system helps in gaseous transport. Oxygen of the inhaled air is absorbed by the blood in the lungs where it combines with the haemoglobin present in RBCs. The Oxygen is carried from lungs to the body tissues where the Oxygen is utilised and Carbon dioxide is released.

Question 2

What factors are most likely to affect the breathing rate?

Answer

Some of the factors that affect the breathing rate are:

  1. While exercising or doing intense physical activity, the body requires more energy due to which the demand of oxygen increases. This increases the rate of breathing of the person.
  2. While sleeping and resting, the breathing rate decreases as the body requires less energy.
  3. Allergic reactions increase the rate of breathing as allergic reactions narrow the nasal passage leading to a demand for more oxygen.
  4. Stress and anxiety increases the breathing rate as the stress hormones trigger the body's fight or flight response.

Question 3

What happens to the energy liberated during respiration?

Answer

The energy liberated during respiration is not all in the form of heat but a large part of it is converted into chemical energy in the form of ATP (Adenosine Triphosphate). This energy is utilised by the body cells for a vast variety of activities like:

  1. Digestion of food.
  2. Production of enzymes.
  3. Contraction of muscles for movement.
  4. Conduction of electrical impulse in a nerve cell.
  5. Production of new cells by cell division.
  6. Keeping the body warm in warm-blooded animals.

Question 4

What do you understand by inhalation and exhalation? How are they different from each other?

Answer

Inhalation is the physical process by which the air containing oxygen is drawn into the lungs.

Exhalation is the physical process by which the air containing carbon dioxide is forced out from the lungs.

Differences between Inhalation and Exhalation are:

InhalationExhalation
Ribs move upwards and outwards.Ribs move downwards and inwards.
Diaphragm is pushed downwards and flattens.Diaphragm moves upwards and becomes dome-shaped.
Volume of chest cavity increases.Volume of chest cavity decreases.
Lungs expand, air pressure becomes low.Size of the lungs reduces, air pressure becomes high.
Atmospheric air at a higher pressure rushes into lungs.Air rushes out of the lungs as atmospheric air pressure is lower.

Question 5

What do you understand by the term respiratory diseases? Name any three common respiratory diseases.

Answer

The diseases that affect the respiratory organs of the body making respiration difficult are termed as respiratory diseases.

The three common respiratory diseases are:

  1. Bronchitis
  2. Asthma
  3. Pneumonia

Question 6

State the cause and treatment for the following diseases:

  1. Tuberculosis
  2. Pneumonia
  3. Bronchitis

Answer

  1. Tuberculosis
    Cause — This respiratory infection is caused by bacteria that can spread by air, dust or sputum.
    Treatment — BCG vaccine, antibiotic Streptomycin.

  2. Pneumonia
    Cause — This respiratory disease is mainly caused by bacteria inhaled through air or by contact.
    Treatment — Antibiotic - Penicillin.

  3. Bronchitis
    Cause — This respiratory infection is mainly caused by a virus. Air pollution and smoking can also cause bronchitis.
    Treatment — Drinking plenty of fluids, following a well balanced diet, frequent hand washing and adequate rest can prevent and improve bronchitis.

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