The ventral respiratory group and the dorsal respiratory group make up the respiratory control center. The rhythmic breathing relies on a continuous inspiratory drive from the dorsal respiratory group and intermittent expiratory input from the cerebrum, thalamus, cranial nerves, and ascending sensory tracts of the spinal cord. The chemoreceptors in the central and peripheral systems respond to changes in PaCO2 and pH. Among the chemoreceptors, the carotid and aortic bodies are the only ones that respond to changes in PaO2.

Breathing is affected differently by acute hypoxia and chronic hypoxia because the slow adjustments in cerebrospinal fluid (CSF) [H+] in chronic hypoxia alter the sensitivity to CO2.

Irritant receptors protect the lower respiratory tract by inducing cough in response to particles, chemical vapors, and physical factors. The C fiber J receptors in the terminal respiratory units are stimulated by distortion of the alveolar walls due to lung congestion or edema.

The two primary clinical abnormalities of breathing are obstructive and central sleep apnea.

During moderate exercise, PaO2, PaCO2, and pH remain within normal limits. However, during strenuous exercise, pH falls, which stimulates ventilation, while PaO2 and PaCO2 remain relatively normal.

The mucociliary clearance system consists of various components that play a role in removing xenobiotic substances and particulates.

The characteristics and properties of particles influence their deposition and clearance.

There are different mechanisms of particle deposition.

The mucosal and systemic immune responses can be compared and contrasted.

Immunoglobulin A has unique features that make it well suited for the mucosal environment and protection.

Adaptive and innate immune cells in the respiratory system can be compared and contrasted.

Various metabolic processes occur in the lung.
The respiratory control center is composed of the dorsal respiratory group and the ventral respiratory group. Rhythmic breathing depends on a continuous (tonic) inspiratory drive from the dorsal respiratory group and on intermittent (phasic) expiratory input from the cerebrum, thalamus, cranial nerves, and ascending spinal cord sensory tracts. The peripheral and central chemoreceptors respond to changes in PaCO2 and pH. The peripheral chemoreceptors (carotid and aortic bodies) are the only chemoreceptors that respond to changes in PaO2.
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CO2responsiveness,havebeenimplicated.Placinginfantsontheirbackstosleep(whichreducesthepotentialforCO2rebreathing)hasdramaticallydecreased(butnoteliminated)therateofdeathfromthissyndrome.
3.
Acute hypoxia and chronic hypoxia affect breathing differently because the slow adjustments in CSF [H+] in chronic hypoxia alter sensitivity to CO2.
4.
Irritant receptors protect the lower respiratory tract from particles, chemical vapors, and physical factors, primarily by inducing cough. C fiber J receptors in the terminal respiratory units are stimulated by distortion of the alveolar walls (by lung congestion or edema).
5.
The two most important clinical abnormalities of breathing are obstructive and central sleep apnea.
6.
PaO2, PaCO2, and pH remain within normal limits during moderate exercise; however, during strenuous exercise, pH falls, which stimulates ventilation, whereas PaO2 and PaCO2 remain relatively normal.
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Wine JJ. Parasympathetic control of airway submucosal glands: central reflexes and the airway intrinsic nervous system. Auton Neurosci. 2007;133:35-54.
Upon completion of this chapter, the student should be able to answer the following questions: 1.
Describe the components of the mucociliary clearance system and their role in the removal of xenobiotic substances and particulates.
2.
Explain how particle characteristics and properties influence their deposition and clearance.
3.
Compare and contrast the major mechanisms of particle deposition.
4.
Compare and contrast the mucosal and systemic immune responses.
5.
Describe unique features of immunoglobulin A and why it is well suited for the mucosal environment and protection.
6.
Compare and contrast adaptive and innate immune cells in the respiratory system.
7.
Describe the various metabolic processes in the lung.