Overview
This lecture explains the oxygen dissociation curve, detailing how oxygen is released from hemoglobin in different conditions and the impact of exercise on this process.
Oxygen Dissociation Curve Basics
- Oxygen dissociation refers to the tendency of oxygen to leave hemoglobin.
- X-axis: partial pressure of oxygen; Y-axis: percentage of hemoglobin saturated with oxygen.
- In arterial blood, hemoglobin is almost fully saturated (97-100%), with high partial pressure of oxygen.
- Arterial blood remains saturated because arteries are impermeable to oxygen diffusion.
Role of Capillaries and Venous Blood
- At capillary beds, partial pressure of oxygen decreases as oxygen diffuses into tissues.
- The drop in hemoglobin saturation in veins (venous blood) indicates oxygen has been delivered to tissues.
- At rest, venous blood hemoglobin is about 70% saturated, showing oxygen delivery at rest.
Effect of Exercise on Oxygen Delivery
- During exercise, muscle tissues experience lower pH (more acidic), increased CO2, lactic acid, and higher temperature.
- These changes shift the oxygen dissociation curve to the right (Bohr shift).
- A rightward shift means hemoglobin releases more oxygen to tissues during exercise.
The Bohr Shift
- Bohr shift: rightward shift of the oxygen dissociation curve due to low pH, high CO2, high lactic acid, and increased temperature.
- This results in greater oxygen delivery to muscles during exercise, as oxygen dissociates more easily from hemoglobin.
Key Terms & Definitions
- Oxygen Dissociation — The process by which oxygen leaves hemoglobin to enter tissues.
- Partial Pressure — The concentration of a particular gas in a mixture of gases.
- Hemoglobin Saturation — The percentage of hemoglobin molecules bound to oxygen.
- Bohr Shift — The rightward shift of the oxygen dissociation curve under acidic, high CO2, or high temperature conditions, leading to increased oxygen release.
- Arterial Blood — Oxygen-rich blood in the arteries, usually fully saturated with oxygen.
- Venous Blood — Oxygen-poor blood in veins, with lower hemoglobin saturation.
Action Items / Next Steps
- Review the oxygen dissociation curve and its shifts under different conditions.
- Be prepared to explain the Bohr shift and its significance during exercise.
- Practice sketching and labeling the oxygen dissociation curve for both resting and exercising states.