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Baroreceptors, Chemoreceptors, and the Medulla Adjust Heart Rate by Feedback
- Heart rate is regulated to keep homeostasis, using baroreceptors, chemoreceptors, and the medulla oblongata.
- These receptors monitor blood pressure, blood pH, and the levels of oxygen and carbon dioxide.
Analogy
- Think of the heart as a car engine.
- Baroreceptors and chemoreceptors are sensors reading speed and fuel; the medulla is the driver adjusting the throttle for a smooth ride.
Two Sensor Types Track Pressure and Blood Chemistry
Baroreceptors Monitor Blood Pressure
- Baroreceptors are pressure-sensitive nerve endings in the walls of major arteries, such as the aorta and carotid arteries.
- They detect pressure changes by sensing the stretch of the arterial walls.
- High blood pressure: baroreceptors increase their firing rate.
- Low blood pressure: baroreceptors decrease their firing rate.
Example
- When you stand up quickly, blood pressure drops for a moment.
- Baroreceptors detect this and trigger a rise in heart rate to restore normal pressure.
Chemoreceptors Monitor Blood Chemistry
- Chemoreceptors detect changes in blood pH and in oxygen and carbon dioxide levels.
- They sit in the aortic bodies and carotid bodies.
- Low oxygen or high carbon dioxide: chemoreceptors increase their firing rate.
- High oxygen or low carbon dioxide: chemoreceptors decrease their firing rate.
Note
- Chemoreceptors are especially sensitive to carbon dioxide, because rising CO2 lowers blood pH and causes acidosis.
