Explaining the Link Between Physical Activity & Breathing: Extended
Extended Tier Only
- Frequency and depth of breathing increase when exercising
- This is because muscles are working harder and aerobically respiring more to keep up with the energy demand:
- They need more oxygen to be delivered to them
- Carbon dioxide needs to be removed
Mechanism for increasing breathing during exercise
- The rate of respiration increases in muscle cells when exercising heavily
- CO2 is a product of aerobic respiration, so CO2 levels increase in the muscle cells
- This CO2 diffuses out of the cells into the blood plasma
- CO2 in solution causes a slight drop in pH so the blood becomes slightly more acidic
- The blood flows around the circulatory system and passes to the brain where the increased carbon dioxide levels are detected by receptors in the brain
- Receptors are cells that detect changes in the body
- The receptors in the brain can detect changes in blood gas (CO2) levels, as well as changes in pH
- The brain sends nerve impulses to the diaphragm and the intercostal muscles to increase the rate and depth of muscle contraction
- The rate of inspiration increases, along with the volume of air moved in and out with each breath
- The result is greater absorption of oxygen and removal rate of carbon dioxide
- This supports the increased rate of respiration in the exercising muscle cells
Exam Tip
Be sure not to confuse the terms respiration and breathing in this topic:
- Respiration is a series of chemical reactions that releases energy from food
- Breathing is the mechanism for moving air in and out of the lungs; this supports the chemical reactions of respiration