The airways into and out of the lungs and the lungs themselves make up your respiratory system. This system allows the exchange of gases --- namely oxygen and carbon dioxide --- through the continuous act of breathing. This process brings in oxygen, which is used by your cells, and removes carbon dioxide, a waste product of reactions in your cells. Your rate of respiration will change in response to different factors, one of which is exercise.
Respiration Rate
Respiration rate is controlled by the brain. The medulla has a rhythmicity center which contains neurons that stimulate both inspiration and expiration. The I neurons cause inspiration --- breathing in --- while the E neurons control expiration --- breathing out. E neurons create exhalation by inhibiting the I neurons, blocking inhalation, Eastern Kentucky University course material explains. As you exercise, receptors in the aorta and carotid arteries sense the increased carbon dioxide levels. This information is transmitted to the medulla and the rhythmicity center is activated, causing an increase in respiration rate.
Gas Exchange
The movement of carbon dioxide out of the blood and of oxygen from the lungs to the blood depends on the concentration of the gases in the alveoli --- thin-walled air sacs in the lungs. Breathing brings in oxygen from the air, keeping the concentration of oxygen in the alveoli high, and removing the carbon dioxide, keeping that concentration low. Diffusion causes the gases to move from the area of high concentration to an area of lower concentration, so oxygen moves out of the alveoli into the blood, and carbon dioxide travels out of the blood into the alveoli, following the concentration gradient. As your respiration rate increases with exercise, the rate of gas exchange correspondingly increases.
Deeper Breathing During Exercise
The contraction of external intercostal muscles, the muscles between your ribs, and the flattening of the diaphragm at the bottom of the ribs cause the thoracic cavity to expand during inspiration, forcing air into the lungs. The amount of air found in the entire respiratory system forms what is known as the anatomical dead space, explains James Madison University course material, and the concentration of gases in this system causes you to breath more deeply during exercise, allowing more oxygen to get to the alveoli and eventually to your tissues.
Four Steps of Respiration
There are four steps of respiration: Breathing, also called ventilation; exchange of gases in the lungs; blood circulation between the lungs and your tissues; and gas exchange between your tissues and your blood. Each of these steps speeds up as you exercise, ensuring that your working muscles receive the additional they oxygen need.
