Sample Respiration Q

Diagram 6.1 shows the part of the regulatory mechanism of oxygen and carbon dioxide contents in the body.

i) Based on the diagram, explain how the concentration of carbon dioxide in the blood is regulated during a vigorous activity.

[8 marks]

Sample answer

P1- During vigorous activity, the concentration / the partial pressure of carbon dioxide increases as a result of active cellular respiration

P2- the carbon dioxide react with water to form carbonic acid which results in a drop in the pH level of the blood and tissue fluid that bathing the brain
P3- The drop in pH is detected by the central chemoreceptors in the medulla oblongata
P4- and detected by peripheral chemoreceptors ( carotid bodies and aortic bodies )
P5-The central chemoreceptors and pheripheral receptors send nerve impulses to the respiratory centre in the medulla oblongata
P6- The respiratory centre sends nerve impulses to the diaphragm and the intercostal muscles, causing the respiratory muscle to contract and relax faster
P7- As a result, the breathing and ventilation rate increase causes more oxygen inhaled and the oxygen concentration return to the normal level
P8- As excess carbon dioxide is eliminated from the body, the carbon dioxide concentration and pH value of the blood return to normal level

ii) Explain why the pulse rate takes several minutes to return to normal after a vigorous activity.

[4 marks]

Sample answer

P1- After vigorous activity, the pulse rate takes several minutes to return to normal because during the activity the oxygen intake is not able to meet the oxygen demand of the body.

P2- Respiration has to take place anaerobically/anaerobic respiration occur
P3- As a result, lactic acid accumulates in the muscle.
P4- So more oxygen is needed to oxidize the lactic acid and to provide the energy for the recovery of the muscle