How is respiration regulated ?
The respiration is regulated in the following ways :
The neural system is involved in regulating the respiration.
i. Respiratory rhythm centre - A specialised centre present in the medulla region of the brain is primarily responsible for the regulation of respiration.
ii. Pneumotaxic centre - in the pons region of the brain moderates the functions of the respiratory rhythm centre. Neural signal from this centre can reduce the duration of inspiration and thereby alter the respiratory rate.
iii. A chemosensitive area situated adjacent to the rhythm centre which is highly sensitive to CO2 and hydrogen ions. Increase in these substances can activate the centre which signals the rhythm centre to make the necessary adjustments in the respiratory process by which these substances can be eliminated.
iv. Aortic arch and carotid artery receptore also recognise changes in CO2 and H+ concentration and send necessary signals to the rhythm centre for necessary actions. Oxygen plays a vital role in the regulation of respiratory rhythm.
Vital capacity : (V.C) It is the total volume of air that can be expelled from the lungs after first filling the lungs to the maximum and then exhaling the same to the maximum :
VC = TV + IRV + ERV
= 500 + 2000 to 2500 + 1000 to 1500 = 3500 to 4500 ml.
Significance of V.C. : Vital capacity of a person gives important clues for diagnosing a lung problem. Measurement of this capacity helps the doctor to decide about the possible causes of the diseases and about the line of treatment. It determines the stamina of sportsmen and mountain climbers. The greater the vital capacity more is energy available to body. Sportsperson or mountain dwellers have higher vital capacity. Young persons have more vital capacity than aged.
Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern ?
Oxygen dissociation curve is the sigmoid curve obtained when the percentage saturation of haemoglobin with O2 is plotted against the partial pressure of oxygen pO2. It helps in the study of the effect of factors like pCO2, H+ concentration etc. on binding of oxygen with haemoglobin.
The binding of oxygen to haemoglobin is in such a way that the binding of the first oxygen oxygen molecule binds to the haemoglobin, it increases the affinity for the second molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen and this gives the curve a sigmoid shape.