Central Chemoreceptors: Examples of Neural Respiratory Control

📚 Central Chemoreceptors: Quick Study Guide

• 🧠 Central chemoreceptors are located in the medulla oblongata of the brainstem.
• 🌡️ They primarily respond to changes in pH and $pCO_2$ (partial pressure of carbon dioxide) in the cerebrospinal fluid (CSF).
• 🧪 An increase in $pCO_2$ or a decrease in pH stimulates these receptors.
• 📈 Stimulation leads to increased respiratory rate and depth to expel excess $CO_2$.
• ⚖️ The blood-brain barrier is permeable to $CO_2$ but less so to $H^+$, so $CO_2$ levels are the main driver.
• 🧬 The reaction is: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$.
• 💡 This mechanism helps maintain acid-base balance in the body.

📝 Practice Quiz

1. Which of the following is the primary stimulus for central chemoreceptors?
   1. A) Increased blood glucose
   2. B) Decreased blood oxygen ($pO_2$)
   3. C) Increased cerebrospinal fluid $pCO_2$
   4. D) Increased blood pressure
2. Where are central chemoreceptors located?
   1. A) Aortic arch
   2. B) Carotid body
   3. C) Medulla oblongata
   4. D) Peripheral nerves
3. What is the primary effect of stimulating central chemoreceptors?
   1. A) Decreased heart rate
   2. B) Increased respiratory rate
   3. C) Decreased blood pressure
   4. D) Increased urine output
4. Which of the following crosses the blood-brain barrier more easily, influencing central chemoreceptors?
   1. A) $H^+$
   2. B) $HCO_3^-$
   3. C) $CO_2$
   4. D) $O_2$
5. What does an increase in $pCO_2$ in the cerebrospinal fluid directly lead to?
   1. A) Alkalosis
   2. B) Acidosis
   3. C) Neutral pH
   4. D) No change in pH
6. Which equation best represents the reaction that central chemoreceptors respond to?
   1. A) $O_2 + Hb \rightleftharpoons HbO_2$
   2. B) $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$
   3. C) $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$
   4. D) $NaCl \rightleftharpoons Na^+ + Cl^-$
7. Why is the sensitivity of central chemoreceptors to $H^+$ ions lower compared to $CO_2$?
   1. A) $H^+$ ions are actively transported out of the brain.
   2. B) $H^+$ ions bind directly to hemoglobin.
   3. C) The blood-brain barrier is less permeable to $H^+$ ions.
   4. D) $H^+$ ions are immediately buffered by proteins in the CSF.