Feedback Control of Heart Rate Following Sensory Input from Baroreceptors and Chemoreceptors
- The regulation of heart rate is crucial for maintaining homeostasis, and this process is controlled through a complex feedback mechanism involving baroreceptors, chemoreceptors, and the medulla oblongata in the brain.
- These sensory receptors monitor specific physiological variables such as blood pressure, blood pH, and the concentration of oxygen (O2) and carbon dioxide (CO2).
- Think of your heart as a car engine.
- Baroreceptors and chemoreceptors are like sensors that monitor speed and fuel levels, while the medulla acts as the driver, adjusting the throttle to maintain a smooth ride.
Baroreceptors and Chemoreceptors Are The Body’s Sensors
Baroreceptors Monitors Blood Pressure
- Baroreceptors are pressure-sensitive nerve endings located in the walls of major arteries, such as the aorta and carotid arteries.
- They detect changes in blood pressure by sensing the stretch of the arterial walls.
- High blood pressure: Baroreceptors increase their firing rate.
- Low blood pressure: Baroreceptors decrease their firing rate.
- When you stand up quickly, blood pressure drops momentarily.
- Baroreceptors detect this change and trigger a response to increase heart rate and restore normal pressure.
Chemoreceptors Monitors Blood Chemistry
- Chemoreceptors detect changes in blood pH and the concentrations of oxygen ($O_2$) and carbon dioxide ($CO_2$).
- They are located in the aortic bodies and carotid bodies.
- Low $O_2$ or high $CO_2$: Chemoreceptors increase their firing rate.
- High $O_2$ or low $CO_2$: Chemoreceptors decrease their firing rate.
Chemoreceptors are especially sensitive to changes in $CO_2$ levels, as increased $CO_2$ lowers blood pH, leading to acidosis.
The Medulla: The Control Center
Definition
Medulla Oblongata
Part of the brainstem responsible for regulating involuntary functions, including heart rate, blood pressure, and respiration.
- The medulla oblongata, located in the brainstem, is the control center for vital functions such as heart rate regulation, breathing, and blood pressure maintenance.
- It processes sensory input from both baroreceptors and chemoreceptors and integrates this information to send the appropriate nerve impulses to the heart.
- For high blood pressure, the medulla will send signals to decrease heart rate and induce vasodilation to lower the pressure.
- For low blood pressure, it will send signals to increase heart rate and induce vasoconstriction to raise the pressure.
- For low oxygen or high carbon dioxide levels, the medulla will increase heart rate and stroke volume to improve oxygen delivery and CO2 removal.
It’s essential to remember that the medulla is the integration center that processes input from both baroreceptors and chemoreceptors, then coordinates the appropriate response by sending nerve impulses to the heart.
How Feedback Control Works
1. Baroreceptor Feedback Loop
- High blood pressure:
- Baroreceptors increase firing.
- Signals are sent to the medulla.
