Chapter 10 - Ventilation Control

Which two structures in the brainstem control ventilation?

The Pons and Medulla Oblongata

What is the main function of the Pons in ventilation control?

It modulates breathing rhythm and fine-tunes respiratory patterns

What does the Pneumotaxic Center do?

Limits inhalation and prevents over-inflation of the lungs

What does the Apneustic Center do?

Promotes prolonged or deeper inhalation

What is the function of the Medulla Oblongata in ventilation?

Contains the primary respiratory control centers that automatically regulate breathing

What does the Dorsal Respiratory Group (DRG) control?

Basic, involuntary breathing by sending signals to the diaphragm to initiate inhalation

What does the Ventral Respiratory Group (VRG) control?

Forced breathing during exercise or speech and both inhalation and exhalation

What does NANC stand for?

Non-Adrenergic Non-Cholinergic system

What is the NANC system?

A “third nervous system” within the autonomic nervous system that controls airway tone independent of adrenergic or cholinergic pathways

What are the two types of NANC pathways?

Inhibitory (i-NANC) and Excitatory (e-NANC)

What is the function of the i-NANC pathway?

Bronchodilation – relaxation of bronchial smooth muscle

Which neurotransmitters are released by the i-NANC pathway?

Nitric Oxide (NO) and Vasoactive Intestinal Peptide (VIP)

What are the effects of NO and VIP?

They relax smooth muscle (via vasodilation), help control gastrointestinal function, and limit mast cell degranulation to reduce inflammation

What does “NO and VIP are co-transmitters of ACh” mean?

They work alongside acetylcholine to fine-tune autonomic responses

What is the function of the e-NANC pathway?

Bronchoconstriction – contracts airway smooth muscle

Which chemicals are released by e-NANC neurons?

Substance P (SP), Neurokinin A (NKA), and Calcitonin Gene-Related Peptide (CGRP)

What are the effects of e-NANC activation?

Bronchoconstriction, vasodilation, increased vascular permeability, and mucus secretion – often via C-fiber stimulation

What is the role of chemoreceptors in ventilation?

They monitor chemical changes in blood and CSF to adjust breathing

What are the two types of chemoreceptors?

Central and Peripheral chemoreceptors

Where are central chemoreceptors located?

In the medulla oblongata

What do central chemoreceptors respond to?

Changes in CO₂ and H⁺ in the CSF (but not to O₂ directly)

How does CO₂ affect the central chemoreceptors?

CO₂ crosses the blood–brain barrier and forms H⁺ ions, lowering pH in the CSF; this stimulates the chemoreceptors to increase ventilation

Can H⁺ and HCO₃⁻ cross the blood–brain barrier?

No, only CO₂ can cross, which triggers the pH change that stimulates the receptors

Where are the peripheral chemoreceptors located?

Carotid bodies (at the bifurcation of the common carotid artery) and Aortic bodies (above and below the aortic arch)

Which nerves carry signals from the peripheral chemoreceptors?

Glossopharyngeal nerve (from carotid bodies) and Vagus nerve (from aortic bodies)

What stimulates peripheral chemoreceptors?

Primarily low PaO₂ (< 60 mm Hg), and to a lesser extent ↑ PaCO₂ and ↓ pH

What is the response to hypoxemia detected by peripheral chemoreceptors?

Signals are sent to the medulla to increase ventilation

What are pulmonary receptors?

Sensory receptors in the lungs that send impulses to the medulla to adjust breathing patterns and protect the airways

Where are SARs located?

In the smooth muscle of bronchi and bronchioles

What stimulates SARs?

Lung inflation; they continue to fire as long as the lung is stretched

What is the reflex associated with SARs?

Hering–Breuer Inflation Reflex – inhibits further inspiration to prevent over-inflation

Where are RARs found?

In the larynx, trachea, carina, and main bronchi

What stimulates RARs?

Lung deflation or irritants (smoke, chemicals)

What responses can RAR stimulation cause?

Coughing, bronchoconstriction, mucus secretion, and deep inspiration (Hering–Breuer Deflation Reflex)

What are C-fibers?

Mechanosensitive and chemosensitive receptors triggered by irritants, inflammation, or stretch

Where are bronchial C-fibers found and what do they cause when activated?

In bronchi; cause bronchoconstriction, mucus production, and cough

Where are J-receptors located and what do they respond to?

In alveolar walls near capillaries; respond to hypoxemia → cause rapid, shallow breathing

What stimulates irritant receptors?

Dust, smoke, chemicals, cold air, or mechanical contact in airway epithelium

What are peripheral proprioceptors?

Position sensors in muscles, joints, and tendons that increase respiratory drive during movement or exercise

What are muscle spindle fibers and where are they found?

Stretch receptors in the diaphragm and intercostals that help adjust muscle force during increased load

What are arterial baroreceptors and their function?

Pressure sensors in the aortic arch and carotid sinus that adjust ventilation in response to blood-pressure changes