Lesson 21: Peripheral Chemoreceptors Overview

Lesson 21: Peripheral Chemoreceptors

  • Location: Carotid bodies (common carotid artery bifurcation), transverse aortic arch.

  • Chief Responsibility: Monitor hypoxemia (PaO2 < 60 mmHg).

    • Do not respond to SaO2 or CaO2.

  • Secondary Responsibilities: Monitor PaCO2, H+, and perfusion pressure.

Hypoxic Ventilatory Response

  • Mechanism:

    1. PaO2 < 60 mmHg closes K+ channels in Type 1 Glomus cells.

    2. Increases resting membrane potential and opens Ca2+ channels.

    3. Increases neurotransmitter release (ACh and ATP).

    4. Action potential propagated via Hering's nerve to glossopharyngeal nerve (CN IX).

    5. Terminates in medulla's inspiratory center; increases minute ventilation to restore PaO2.

Conditions that Impair Hypoxic Ventilatory Response

  • Carotid Endarterectomy: Severing of the afferent limb leads to recalibration time.

  • Anesthetics (0.1 MAC): Depress hypoxic ventilatory drive; risk postoperative hypoxemia.

  • Volatile Anesthetics: Impair diaphragmatic, intercostal, and upper airway muscle function.

Conditions that Do NOT Impair Hypoxic Ventilatory Response

  • Anemia and Carbon Monoxide Poisoning: Cause reduced CaO2 but typically maintain normal PaO2, thus do not stimulate hypoxic response.