7 - CONTROLLING BREATHING RATE

Question 1

What part of the brain controls breathing rate?

Answer 1

The medulla oblongata

Question 2

1st point

Answer 2

The inspiratory centre in the medulla oblongata sends nerve impulses to the intercostal and diaphragm muscles to make them contract

Question 3

2nd point

Answer 3

This increases the volume of the lungs, which lowers the pressure in the lungs

Question 4

3rd point

Answer 4

The inspiratory centre also sends nerve impulses to the expiratory centre, inhibiting it

Question 5

4th point

Answer 5

Air enters the lungs due to pressure difference (between lungs and air outside)

Question 6

5th point

Answer 6

As the lungs inflate (due to the air coming in), the stretch receptors (in the lungs) are stimulated. The stretch receptors send nerve impulses back to the medulla oblongata, thus inhibiting the inspiratory centre.

Question 7

6th point

Answer 7

Since the expiratory centre is now no longer inhabited, it sends impulses to the diaphragm and intercostal muscles to relax, causing gut lungs to deflate, expelling air.

Question 8

7th point (final)

Answer 8

As the lungs deflate, the stretch receptors become inactive, and the inspiratory centre is no longer inhibited and the cycle starts again.

Question 9

how does exercise trigger an increase in breathing rate?

Answer 9

1) Exercise causes the levels of CO2 in the blood to increase, thus decreasing the pH of the blood
2) The chemoreceptors in the medulla oblongata, aortic bodies, carotid bodies that are sensitive to changes in blood pH detect this change
3) they send impulses back to the medulla oblongata, which then sends more frequent nerve impulses to the intercostal muscles and diaphragm, increasing the rate of breathing
4) gaseous exchange is therefore now sped up