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NEET Biology Breathing and Exchange of Gases

Breathing and Exchange Of Gases PDF Notes, Important Questions and Synopsis

SYNOPSIS

  • Human Respiratory System


  • Respiratory Volumes and Capacities


    Terms

    Description

    Tidal Volume (TV)

    • It is the volume of air inspired or expired during normal respiration.

    • The tidal volume is approximately 500 ml.

    Inspiratory Reserve Volume (IRV)

    • It is the additional volume of air a person can inspire by a forcible inspiration.

    • A person can inhale 2500 to 3000 ml of air over and above the tidal volume.

     Expiratory Reserve Volume (ERV)

    • It is the additional volume of air a person can expire by a forcible expiration.

    • A person can expire 1000 to 1100 ml of air over and above the tidal volume.

    Residual Volume (RV)

    • Even after a forcible expiration, some volume of air remains in the lungs which is called the residual volume.

    • About 1100 to 1200 ml air remains in the lungs.

    Inspiratory Capacity (IC)

    • It is the volume of air which a person can inspire after normal expiration.

    • This includes tidal volume and inspiratory reserve volume (TV + IRV).

    Expiratory Capacity (EC)

    • It is the total volume of air a person can expire after a normal inspiration.

    • This includes the tidal volume and expiratory reserve volume (TV + ERV).b

    Functional Residual Capacity (FRC)

    • It is the volume of air which is left in the lungs after normal expiration.

    • It is the sum of expiratory reserve volume (ERV) and residual volume (RV).

    Vital Capacity (VC)

    • It is the maximum volume of air a person can breathe in after a forced expiration.

    • This is the sum of expiratory reserve volume (ERV), tidal volume (TV) and inspiratory reserve volume (IRV).

    Total Lung Capacity (TLC)

    • It is the amount of air in the lungs after maximum inspiration.

    • It is the sum of the vital capacity and the residual volume.

  • Transport of Oxygen
    • About 97% of oxygen is transported in the blood in the form of oxyhaemoglobin.
    • Each haemoglobin molecule can combine with four oxygen molecules to form oxyhaemoglobin.
    • Rest 3% is in the dissolved state in plasma.
    • Factors such as H+ ion concentration, pO2, pCO2 and temperature interfere with the binding of oxygen with haemoglobin.
  • Transport of Carbon Dioxide
    • CO2 is carried by blood in three forms:
    • As a simple solution: About 5–10% of CO2 of the total blood dissolves in plasma and is carried as a simple physical solution.
    • As bicarbonate ions: CO2 diffuses into the blood and reacts with water to form carbonic acid. Carbonic acid dissociates into bicarbonate HCO3- and H+ ions. These bicarbonate ions are carried by the plasma.
    • As carbamino-haemoglobin: CO2 combines loosely with the globin part of the reduced haemoglobin to form carbamino-haemoglobin. When pO2 is high and pCO2 is low in alveoli, CO2 dissociates from carbamino-haemoglobin; hence, CO2 bound to haemoglobin is released in the alveoli.
  • Regulation of Respiration
    • The respiratory rhythm centre present in the medulla oblongata is responsible for the regulation of respiratory rhythm.
    • The pneumotaxic centre present in the pons regulates or moderates the functions of the respiratory rhythm centre.
    • A chemosensitive area is located adjacent to the rhythm centre and is highly sensitive to CO2 and hydrogen ions.