Breathing

Question 1

minute ventilation

Answer 1

the volume of air breathed in or out of the lungs per minute

Question 2

tidal volume

Answer 2

the volume of air in each normal breath

Question 3

breathing rate

Answer 3

the number of breaths in a minute

Question 4

equation

Answer 4

minute ventilation = tidal volume + breathing rate

Question 5

how does the nervous system control inhalation

Answer 5

1. the ventilation centre of the medulla transmits nerve impulses to the external intercostal and diaphragm muscles to make them contract using phrenic nerves
2. this increases the volume of the lungs which lowers the pressure in the lungs so air enters the lungs due to the pressure difference between the lungs and the outside
3. as the lungs inflate the stretch receptors in the lungs are stimulated to send impulses to the medulla

Question 6

how does the nervous system control exhalation

Answer 6

1. the impulses received inhibit the ventilation centre from sending impulses to the muscles so the muscle stop contacting
2. the intercostal and diaphragm muscles relax
3. relaxation of muscles decreases the volume of the lungs which increases the pressure in the lungs
4. air leaves the lungs due to the pressure difference between the lungs and the outside air
5. as the lungs deflate stretch receptors become inactive and the cycle starts again

Question 7

breathing during exercise

Answer 7

• increase in blood co2 concentration causes a decrease in blood pH
• chemoreceptors in medulla detects this and transmit impulses to the ventilation centre of the medulla to-then send more frequent impulses to the intercostal muscle

Question 8

how does a spirometer calculate respiratory minute ventilation

Answer 8

find the difference in peak to trough to fine the tidal volume then count the number of peaks in a minute to find breathing rate and then times tidal volume with breathing rate to get minute ventilation

Question 9

how does a spirometer find oxygen consumption per minute

Answer 9

find the difference in volume of one peak compared to a subsequent one and divide by time between the two peaks and multiply by 60