Link Between Physical Activity & Breathing | Biology for GCSE/IGCSE - Year 11 PDF Download

Explaining the Link Between Physical Activity & Breathing

• Frequency and depth of breathing increase when exercising
• This is because muscles are working harder and aerobically respiring more. They require more oxygen to be delivered to them and carbon dioxide to be removed to meet the increased energy demand.
• If the energy demand is not met, muscles will switch to anaerobic respiration, leading to the production of lactic acid.
• After exercise, the accumulated lactic acid in muscles needs to be eliminated as it reduces the pH of cells and can deactivate enzymes responsible for cellular reactions.
• Lactic acid removal necessitates its combination with oxygen, a process known as 'repaying the oxygen debt.'
• The duration it takes for breathing rate and depth to return to normal after exercise reflects the amount of lactic acid generated during exercise and the magnitude of the oxygen debt that must be repaid.

Mechanism for increasing breathing during exercise

• During heavy exercise, the rate of respiration increases in muscle cells.
• As a byproduct of aerobic respiration, carbon dioxide (CO₂) levels rise within the muscle cells.
• CO₂ diffuses out of the cells into the blood plasma, leading to a slight decrease in pH and making the blood slightly more acidic.
• The acidic blood containing increased CO₂ levels travels through the circulatory system to the brain.
• Chemoreceptors in the brain's medulla oblongata detect these elevated levels of carbon dioxide.
• Chemoreceptors are specialized cells that sense changes in chemicals within the body, including variations in blood gas levels and pH.

Role of Chemoreceptors in Respiration

• Chemoreceptors play a crucial role in detecting chemical alterations in the body.
• They are capable of monitoring changes in blood gas levels and pH.
• Located in the medulla oblongata of the brain, chemoreceptors are sensitive to shifts in CO2 levels.

Effects on Breathing Pattern

• The brain responds by sending nerve signals to the diaphragm and intercostal muscles.
• These signals prompt an increase in both the rate and depth of muscle contractions.
• Resulting in a rise in the rate of inspiration and an increase in the volume of air exchanged during each breath.

Enhanced Oxygen Intake and CO₂ Removal

• Ultimately, this process leads to improved oxygen absorption and a faster elimination of carbon dioxide.
• These adjustments support the heightened rate of respiration required by the exercising muscle cells.

Support for Increased Respiration in Exercising Muscle Cells

• This concept aids in boosting the rate of respiration within the muscle cells during exercise.

Understanding Respiration vs. Breathing

It's crucial to differentiate between respiration and breathing:

• Respiration: Encompasses a series of chemical reactions that extract energy from food sources.
• Breathing: Involves the process of inhaling and exhaling air to facilitate the chemical reactions of respiration.

Key Points:

• Respiration involves energy release from food through chemical reactions.
• Breathing enables the movement of air in and out of the lungs, supporting the chemical reactions of respiration.