Question

How does the respiratory rhythm centre help in regulating the carbon dioxide concentration?
i) It helps to direct the respiratory muscles which leads to decreased or increased breathing rate.
ii) It can send signals to the external intercostal muscles and the diaphragm, to increase the breathing rate and the volume of the lungs during inhalation.
iii) It interacts with the aortic body to increase the respiratory rate.

• A. Only i is correct
• B. Both i and ii are correct
• C. Only iii is correct
• D. All are correct

Answer 1

The correct option is D All are correct

The respiratory rhythm centre is located in the medulla in the hindbrain. It is further divided into inspiratory and expiratory groups. Inspiratory group stimulates the external intercostal muscles (respiratory muscles) to contract during inspiration. Expiratory group stimulates the internal intercostal muscles (respiratory muscles) and diaphragm to expire
Another centre present in the brain is called pneumotaxic centre. It is located in the pons in hindbrain. It can moderate the functions of the respiratory rhythm centre.
Neural signals from this centre can reduce the duration of inspiration and thereby alter the respiratory rate. It works via the medullary centres. The pneumotaxic center sends signals to inhibit inspiration that allows it to finely control the respiratory rate. Its signals limit the activity of the phrenic nerve (nerves in the neck and passing through the thorax to the diaphragm) and inhibit the signal of the apneustic center (another pons respiratory centre). It decreases tidal volume. The apneustic center sends signals for inspiration for long and deep breaths. It controls the intensity of breathing and is inhibited by the stretch receptors of the pulmonary muscles at maximum depth of inspiration, or by signals from the pneumotaxic center. It increases tidal volume. This is how the apneustic and pnuemotaxic centers work against each other together to control the respiratory rate and rhythm centre help direct the respiratory muscles which leads to a decreased/increased breathing rate.
It also interacts with the aortic body (chemoreceptors present in the aortic arch) to increase the respiratory rate. The aortic body recognizes changes in carbon dioxide and hydrogen ion concentration in the blood and sends necessary signals to the respiratory rhythm centre for remedial actions.