Question

Chemoreceptors for control of breathing.

Hint:

The central chemoreceptors are primarily sensitive to CO\(_2\) levels and pH, whereas peripheral chemoreceptors are more sensitive to oxygen levels.

Answer 1

Step 1: Understanding Chemoreceptors.
Chemoreceptors are specialized sensory receptors that detect changes in the chemical composition of the blood, particularly levels of oxygen (O\(_2\)), carbon dioxide (CO\(_2\)), and pH. These receptors play a crucial role in regulating the rate and depth of breathing.

Step 2: Types of Chemoreceptors.
There are two main types of chemoreceptors involved in the control of breathing:
1. Peripheral Chemoreceptors: Located in the carotid bodies (at the bifurcation of the carotid artery) and aortic bodies (in the aortic arch), these receptors primarily respond to changes in the partial pressure of oxygen (PaO\(_2\)) and, to a lesser extent, CO\(_2\) and pH. When oxygen levels decrease, these chemoreceptors stimulate the respiratory centers in the brain to increase the rate and depth of breathing.
2. Central Chemoreceptors: Located in the medulla oblongata, these chemoreceptors are primarily sensitive to changes in the partial pressure of CO\(_2\) (PaCO\(_2\)) and pH. An increase in CO\(_2\) levels (and thus a decrease in pH) triggers the central chemoreceptors to stimulate an increase in the rate and depth of breathing to expel excess CO\(_2\).

Step 3: Response to Changes in Blood Gases.
- Low oxygen (hypoxia): Stimulates peripheral chemoreceptors to increase ventilation.
- High CO\(_2\) (hypercapnia): Stimulates both central and peripheral chemoreceptors to increase ventilation.
- Low pH (acidosis): Also stimulates both types of chemoreceptors to increase ventilation to expel CO\(_2\) and restore normal pH levels.

Step 4: Clinical Relevance.
Chemoreceptor sensitivity is critical for maintaining homeostasis in blood gases. In conditions like chronic obstructive pulmonary disease (COPD), chemoreceptor response may be impaired, leading to respiratory issues.