Biology 2 Marks Questions

The volume of air remaining in the lungs after a normal breathing is called Functional residual capacity (FRC). This includes expiratory reserve volume (ERV) and residual volume (RV). ERV=1000 to 1100 ml. RV = 1100 to 1200 ml. Thus, FRC = 2100 to 2300 ml.

Tidal volume is the volume of air inspired or expired with each normal breath. This is about 500 mL in an adult person. It is composed of about 350 mL of alveolar volume and about 150 mL of dead space volume. The alveolar volume consists of air that reaches the respiratory surfaces of the alveoli and engages in gas exchange. The dead space volume consists of air that does not reach the respiratory surfaces. A healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute. Therefore, tidal volume for a healthy human in an hour is 360 – 480 mL of air.

	Vital capacity (VC)		Total lung capacity (TLC)
1.	It is the maximum volume of air that can be exhaled after a maximum inspiration. It includes IC and ERV.	1.	It is the volume of air in the lungs after maximum inspiration. It includes IC, ERV, and residual volume.
2.	It is about 4000 mL in the human lungs.	2.	It is about 5000 – 6000 mL in the human lungs.

	Inspiratory reserve volume (IRV)		Expiratory reserve volume (ERV)
1.	It is the maximum volume of air that can be inhaled after a normal inspiration.	1.	It is the maximum volume of air that can be exhaled after a normal expiration.
2.	It is about 2500 – 3500 mL in the human lungs.	2.	It is about 1000 – 1100 mL in the human lungs.

	Inspiratory capacity (IC)		Expiratory capacity (EC)
1.	It is the volume of air that can be inhaled after a normal expiration.	1.	It is the volume of air that can be exhaled after a normal inspiration.
2.	It includes tidal volume and inspiratory reserve volume. IC = TV + IRV	2.	It includes tidal volume and expiratory reserve volume. EC = TV + ERV

Vital capacity is the maximum volume of air that can be exhaled after a maximum inspiration. It is about 3.5 – 4.5 liters in the human body. It promotes the act of supplying fresh air and getting rid of foul air, thereby increasing the gaseous exchange between the tissues and the environment.

In normal breathing, inspiration is an active process as it is brought about by the contraction of diaphragm and external intercostal muscles, while expiration is a passive process as it simply involves relaxation of inspiratory muscles.

1. Partial pressure of oxygen.
2. Partial pressure of carbon dioxide.
3. Hydrogen ion concentration.
4. Temperature.

Diaphragm and external and internal intercostals muscles of ribs are the important parts involved in creating a pressure gradient between lungs and the atmosphere during normal respiration.

The differences between emphysema and occupational respiratory disorder are as follows:

	Emphysema	Occupationl respiratory disorder
(i)	It is a chronic disorder in which alveoler walls are damaged and respiratory surface is reduce.	It is caused by proliferation of fibrous connective tissue of upper part of lung.
(ii)	One of the major causes of this is cigarette smoking.	It is due to exposure to harmful substances, gas fumes, dust etc.

1. In such industries, the production of dust is so much that the defence mechanism of the body cannot cope with the situation.
2. The workers should wear protective masks to avoid the dust getting into the respiratory system.

1. Inspiration occurs when the intra-pulmonary pressure is lower than the atmospheric pressure.
2. Expiration occurs when the intra-pulmonary pressure is higher than the atmospheric pressure.

1. Cartilaginous rings are incomplete from behind which supports the walls of the trachea and the bronchi to prevent them from collapsing.
2. Pseudostratirted ciliated columnar epithelium is rich in mucus secreting cells.

Two steps of respiration:

1. Inspiration. When the intrapulmonary pressure is less than the atmospheric pressure then air is inspired
2. Expiration. When the intrapulmonary pressure is more than the atmospheric pressure then air is expired.

1. The muscles of the diaphragm are in a relaxed position, making it convex.
2. The internal intercostal muscles are contracting thus, pulling the ribs downward and inward.

The differences between inspiratory reserve volume and expiratory reserve volume are as follows:

	Inspiratory reserve volume	Expiratory reserve volume
(i)	It is additional volume of air a person can inspire by a forcible inspiration after normal inspiration.	It is additional volume of air a person can expire by forcible expiration after normal expiration.
(ii)	It averages 2500 - 3000ml of air.	It averages 1000 - 1100ml of air.

1. Thin squamous epithelium of alveoli.
2. Endothelium of alveolar capillaries.
3. Basement substance in between.

Conducting Part of Respiratory System: The part of respiratory system, starting with the external nostrils up to the terminal bronchioles, constitutes the conducting part. The conducting part transports the atmospheric air to the alveoli, clears it from foreign particles, humidifies and also brings the air to body temperature.

The foul air follows the route given below: Alveoli→ Alveolar ducts → Bronchioles → Bronchi→ Trachea → Larynx → Glottis Pharynx → Internal nares →Nasal chambers → 4 External nares → Atmosphere. The tidal volume increases 4-10 times during excitement and activity.

In males, the lateral movement of thorax constitutes 25% of breathing, while the abdominal movement accounts for 75% breathing. Thus, it is regarded as abdominal breathing. In women, particularly in pregnant women, the entire breathing is through lateral movement of thorax. Thus, breathing in women is regarded as thoracic. The VC is higher in men than in women and in the young ones than in the old persons.

Asthma:

1. It is due to inflammation of bronchi and bronchioles.
2. Difficulty in breathing and wheezing are its symptoms.

Emphysema:

1. It is caused mainly by cigarette smoking.
2. The alveolar walls are damaged and hence, there is a decrease in the respiratory surface for exchange of gases.

The pressure contributed by an individual gas in a mixture of gases, is called partial pressure of gases.

1. The contraction of diaphragm initiates inspiration, as it increases the volume of the thoracic chamber in the antero-posterior axis.
2. Hence, the intra-pulmonary air pressure decreases to less than the atmospheric pressure; hence, air from outside moves into the lungs.

1. Fishes have gills as the respiratory organ (branchial respiration). It allows them to breathe inside water.They use dissolved oxygen in water.
2. Swimmers resort to repeated deep inhalations and exhalations in rapid succession to store oxygen, so that they can swim under water.
3. Respiratory organ of humans are lungs.
4. Rahul is intelligent, good observer, concerned and inquisitive student.

1. The pressure contributed by an individual gas in a mixture of gases, is called the partial pressure of a gas.
2. The factors affecting rate of diffusion include.

1. Solubility of the gas.
2. Thickness of the membrane.

3. It is asthma.

CO2 is transported in the human body in the following ways:

1. In dissolved form about 7%.
2. As bicarbonate ions about 70%.
3. As carbaminohaemoglobin about 20-25%.

1.  

1. 104mm Hg.
2. 95mm Hg.
3. 40mm Hg.

2.  

1. 40mm Hg.
2. 45mm Hg
3. 40mm Hg.

Diffusion membrane consists of:

1. Squamous epithelium of alveoli.
2. Endothelium of alveolar capillaries.
3. Basement membranes between the two.

It's about 0.2mm in thickness.

1. The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shapec diaphragm.
2. It is necessary because any change in the volume of thoracic cavity will be reflected in the pulmonary cavity.

1. Proliferation of fibrous tissues of lungs due to inflammation, is called fibrosis.
2. The inflammation may be caused by the pollutants in one's working place, especially cement or glass factories, coal mines, etc.

1. Occupational disorders are those respiratory disorders caused by the potentially harmful substances/ pollutants present in the air, where a person works. In work places involving breaking or grinding of stones, there is so much of pollutants/ dust that the immune system of the body cannot cope with the situation.
2. Long exposure to such pollutants leads to inflammation and fibrosis of the lungs and lung damage.

	Residual Volume	Functional Residual Capacity
1	It is the volume of air left in the lungs after forceful expiration.	It is the volume of air left in the lungs after normal effortless expkation.
2	This is about 1100-1200ml.	It includes RV + ERV = 1100 + 1100ml.

Factors that affect the oxygen haemoglobin binding are:

1. Partial pressure of oxygen.
2. Partial pressure of carbon dioxide.
3. Hydrogen ion concentration.
4. Temperature.

The differences between vital capacity and total lung capacity are as follows:

	Vital capacity	Total lung capacity
(i)	It is the maximum volume of air a person can breathe in after a forced expiration of the maximum volume of air a person can breathe out after a forced inspiration.	It is the total volume of air accomodated in the lungs and respiratory passage after forced inspiration.
(ii)	It is sum of tidal volume, inspiratory reserve volume and expiratory reserve volume.	It is sum of vital capacity and residual volume.
(iii)	It averages 3400 - 4800 ml.	Il averages 4500 - 6200ml.

Respiratory process is regulated by certain specialised, centres present in hindbrain. Amongst them, pneumotaxis centre is located in the dorsal part of pons varoli of the brain, can reduce the duration of inspiration and thus, alter the respiratory rate.

1. Fishes and Pita, etc.
2. Insects, centipedes and millipedes, etc.
3. Certain bacteria, parasitic worms (e.g., Ascaris and tapeworm), etc.