Q4. Assertion: a rise in blood CO increases the rate of breathing. Reason: the chemosensitive area, highly sensitive to CO and H, signals the respiratory rhythm centre when they increase. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 190).
Q5. Name the two sites, outside the brain, of receptors that sense changes in CO and H concentration.
The aortic arch and the carotid artery (NCERT page 190).
Q6. How does a signal from the pneumotaxic centre change breathing?
It can reduce the duration of inspiration and so alter the respiratory rate (NCERT page 190).