José

Question 1

What is the effect of the medulla in the control of heart rate?

Answer 1

It increases heart rate when there is a decrease in blood pH, and decreases heart rate when blood pressure increases.

Question 2

What is the effect of the medulla in the control of breathing rate?

Answer 2

The inspiratory centre in the medulla sends nerve impulses to the intercostals and diaphragm to make them contract. This increases the volume of the lungs, which lowers the pressure in the lungs. It also send impulses to the expiratory centre. Air enters the lungs due to the pressure difference between the lungs and the air outside. As the lungs inflate, stretch receptors in the lungs are stimulated. Stretch receptors send nerve impulses back to the medulla, these impulses inhibit the action of the inspiratory centre. The expiratory centre then sends nerve impulses to the diaphragm and intercostal muscles to relax. This causes lungs to deflate, expelling air. As the lungs deflate, the stretch receptors become inactive. And the cycle starts again