Overview
This lecture covers how the body regulates carbon dioxide (CO₂) levels in the blood to maintain homeostasis, focusing on the roles of chemoreceptors, blood pH, and corrective actions involving the heart and breathing muscles.
Importance of Regulating CO₂
- The body regulates carbon dioxide, not oxygen, in the bloodstream.
- Controlling CO₂ levels is essential for maintaining the blood's pH within a narrow range.
- Blood pH is crucial because extreme changes can denature enzymes, disrupting metabolic processes.
Location of CO₂ Regulation
- CO₂ is monitored and regulated in blood vessels, not in the lungs.
- Key blood vessels involved are the carotid arteries (in the neck) and the aorta (the body's largest artery).
Regulation Mechanism (Stimulus-Response Pathway)
- Stimulus: An increase in CO₂ levels in the blood triggers the process (e.g., from exercise or shallow breathing).
- Receptors: Chemoreceptors in the carotid arteries and aorta detect increased CO₂ and lowered blood pH.
- Control Center: Chemoreceptors send electrical impulses to the medulla oblongata in the brain.
- Corrective Measures: The medulla instructs the heart to beat faster and breathing muscles (diaphragm and intercostals) to contract more rapidly and deeply.
- Resulting in: Increased exhalation of CO₂ and restoration of blood pH to normal levels (less acidic).
Homeostasis and Blood pH
- Homeostasis maintains internal conditions like CO₂ and pH within narrow limits.
- Excess CO₂ leads to acidosis (acidic blood pH), which is harmful if uncorrected.
- The removal of extra CO₂ makes the blood less acidic (more alkaline), keeping enzyme function intact.
Key Terms & Definitions
- Chemoreceptor — Cells in the aorta and carotid arteries that detect CO₂ and pH changes in the blood.
- Aorta — The largest artery, responsible for transporting blood from the heart to the body.
- Carotid Artery — Artery in the neck supplying oxygenated blood to the brain.
- Medulla Oblongata — Brain region controlling breathing rate and coordinating homeostatic responses.
- Breathing Muscles — Diaphragm and intercostal muscles that enable inhalation and exhalation.
- Acidosis — Condition where blood becomes too acidic due to excess CO₂.
Action Items / Next Steps
- Review and memorize key terms for flashcard or mind map revision.
- Practice explaining the CO₂ regulation pathway using the stimulus, receptor, control center, corrective measure, and effect structure.