Breathing Rate and Brain Control

Breathing Rate

• Breathing rate refers to how quickly or slowly a person inhales and exhales.
• A healthy adult's average breathing rate is 12-20 breaths per minute.
• Breathing rate changes to match oxygen demand or supply.

Role of the Brain

• Breathing is largely involuntary, controlled by the medulla oblongata in the brain stem.
• Higher brain centers can influence breathing, allowing for voluntary control, but this control is temporary.
• Nerve impulses from the brain stem travel down the spinal cord to muscles in the rib cage and diaphragm.
• These impulses trigger the contraction of the diaphragm and external intercostal muscles causing inhalation.
• Stretch receptors in the intercostals signal the brain about inhalation, causing the brain to stop the signal, relaxing the muscles and triggering exhalation.

What Determines Breathing Rate?

• Level of CO2 in the blood: This is the primary driver.
  • Chemical receptors in the brain, carotid artery, and aorta detect CO2 levels and changes in blood pH (more CO2 leads to lower pH).
  • A decrease in blood pH (higher CO2) triggers an increase in breathing rate and volume to remove CO2.
• Level of O2 in the blood: This is a secondary driver.
  • Receptors in arteries monitor O2 levels in the blood.
  • An extremely low O2 level triggers an increase in breathing rate. However, changes in CO2 levels are prioritized.

Factors Affecting Breathing Rate

• Strenuous activity: Increases breathing rate due to higher oxygen need.
• Poor ventilation: Increases CO2 in the air, increasing breathing rate.
• Sickness (colds, emphysema): Decreases the efficiency of breathing, increasing breathing rate.
• High altitude: Reduced oxygen levels and reduced air pressure lead to an increase in breathing rate.