Breathing and Exchange of Gases MCQs for NEET — Zoology Questions with Answers

The respiratory movements are primarily controlled by the medulla oblongata, which is part of the brainstem. The medulla oblongata contains the respiratory centers that regulate the rate and depth of breathing by sending signals to the respiratory muscles.

At higher CO₂ concentration, the oxygen dissociation curve of hemoglobin shifts to the right. This is known as the Bohr effect. Higher levels of CO₂ result in a lower pH, which causes hemoglobin to release oxygen more readily. This shift to the right indicates that, at a given partial pressure of oxygen, hemoglobin will have a lower affinity for oxygen, facilitating oxygen release to tissues.

The chloride shift, also known as the Hamburger phenomenon, is essential for the transport of carbon dioxide (CO₂). When CO₂ enters red blood cells, it is converted to bicarbonate (HCO₃^-) and hydrogen ions (H⁺) by the enzyme carbonic anhydrase. The bicarbonate ions are then exchanged for chloride ions (Cl^-) from the plasma to maintain electrical neutrality, facilitating the transport of CO₂ in the blood.

The volume of air inspired or expired with each normal breath is known as tidal volume. Tidal volume is the amount of air that is inhaled or exhaled during normal, quiet breathing, which is typically about 500 mL in a healthy adult.

The oxygen-hemoglobin dissociation curve shifts to the right when there is a decrease in pH, which indicates increased acidity. This phenomenon is known as the Bohr effect, where higher concentrations of hydrogen ions (lower pH) reduce hemoglobin's affinity for oxygen, facilitating oxygen release to the tissues.

During expiration, the diaphragm relaxes. When the diaphragm relaxes, it moves back to its dome-shaped position, which decreases the volume of the thoracic cavity and increases the pressure, causing air to be expelled from the lungs.

Carbon dioxide is transported from the tissues to the respiratory surface primarily by plasma and erythrocytes. In erythrocytes, CO2 combines with water to form bicarbonate, which is then transported in the plasma. This process helps to maintain acid-base balance in the body.

The respiratory center is located in the medulla oblongata, which is part of the brainstem. This center controls the rate and depth of breathing by sending signals to the respiratory muscles. The medulla oblongata has two main areas involved in respiration: the dorsal respiratory group (DRG) and the ventral respiratory group (VRG).

The correct pathway for air to reach the lungs is: Nostrils → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli. This sequence ensures that the air is properly filtered, warmed, and humidified before reaching the delicate alveolar sacs where gas exchange occurs.

The volume of air breathed in and out during effortless respiration is known as the tidal volume. It represents the normal amount of air exchanged with each breath without any extra effort. For a healthy adult, the tidal volume typically ranges from 500 to 600 milliliters.