Chemoreceptors Regulate Ventilation Rate Through Feedback Control
- The ventilation rate (breathing rate) is tightly regulated by a feedback mechanism that ensures the body maintains proper levels of oxygen (O₂), carbon dioxide (CO₂), and blood pH.
- This control system relies on chemoreceptors that detect changes in blood chemistry and send signals to the respiratory centers in the brainstem, which then adjust breathing rate and depth by stimulating the diaphragm and intercostal muscles.
Definition
pH
pH is a measure of how acidic or basic a solution is, ranging from 0 (very acidic) to 14 (very basic).
Blood pH is tightly regulated between 7.35 and 7.45.
Why Does Blood pH Change?
- Carbon Dioxide and pH
- During cellular respiration, cells produce carbon dioxide ($CO_2$) as a waste product.
- When $CO_2$ dissolves in blood, it forms carbonic acid ($H_2CO_3$), which releases hydrogen ions ($H^+$), lowering pH and making the blood more acidic.
- Exercise and Increased $CO_2$
- During exercise, muscles work harder and produce more $CO_2$.
- This increases acidity, potentially disrupting the optimal pH range.
Central chemoreceptors are more sensitive to $CO_2$ changes, while peripheral chemoreceptors also monitor oxygen levels.
Location of Chemoreceptors
- Central chemoreceptors (major role)
- Located in the medulla oblongata (brainstem)
- Detect changes in blood pH by sensing CO₂ levels in cerebrospinal fluid (CSF)
- Peripheral chemoreceptors (secondary role)
- Located in the carotid bodies (near carotid arteries) and aortic bodies (near aortic arch)
- Detect O₂, CO₂, and pH levels in arterial blood
The Role of Muscles in Ventilation
- Diaphragm: Contracts to expand the chest cavity, drawing air into the lungs.
- Intercostal Muscles: External intercostal muscles lift the ribcage during inhalation. Internal intercostal muscles help with forced exhalation during intense activity.
