Question

1. After exercising, respiratory rate______________(increase or decrease) and breathing holding time _______________(increase or decrease). Explain why.

2. After rebreathing air, respiratory rate______________(increase or decrease) and breath holding time_____________(increase or decrease). Explain why.

3. After hyperventillation, respiratory rate_____________(increase or decrease) and breath holding time____________(increase or decrease). Explain why.

Answer 1

1. After exercise, there occurs increased carbondioxide build up in the body. In other words oxygen is less and pCO2 is high. This High pCO2 stimulates the respiratory centre located in the medulla oblongata to stimulate respiration. Hence the respiration is stimulated and respiratory rate increases.

Breath holding is a procedure in which we hold our breath and all the oxygen gets utilized and no carbondioxide is getting exhaled by the body. So carbondioxide gets retained.

As CO2 is high in the blood, the breath holding time decreases as body cannot tolerate more increase in carbon dioxide.

2. Rebreathing of air means that you have inhaled the same air which you have exhaled before. We all know that the exhaled air has high carbondioxide content and low oxygen. So, as we rebreath, the little oxygen will be utilized and pCO2 will rise as carbon dioxide also gets absorbed. This Increased pCO2 will stimulate the respiratory centre and the respiratory rate increases.

Breath holding time will decrease as more pCO2 is there and body cannot tolerate more increase in concentration of carbondioxide.

3. Hyperventilation means increased respiratory rate. Hyperventilation removes excess carbondioxide from the body. pCO2 decreases in this case. As pCO2 is decreased, the medulla will not be stimulated and hence, respiratory rate will decrease.

Breath holding time will increase as the pCO2 is less and body has more oxygen content which can be used for longer.