Respiratory Physiology: Neurologic Control, Chemoreceptors, V/Q, and ABGs

Is ventilation voluntary or involuntary?

Both. It happens automatically, but you can control it temporarily.

What are the three components of the neurologic control system?

Receptors (sensors), control centers (brain), and effectors (muscles).

Which brainstem structure sets the basic breathing rhythm?

Medulla oblongata.

What is the primary function of the pons?

Fine-tunes breathing and helps control when inhalation ends.

What are the three respiratory groups in the medulla?

Pre-Bötzinger Complex, Dorsal Respiratory Group (DRG), and Ventral Respiratory Group (VRG).

What does the Pre-Bötzinger Complex do?

Acts as the pacemaker that helps generate the breathing rhythm.

What is the role of the DRG?

Controls inspiration during quiet, normal breathing.

What is the role of the VRG?

Helps with forceful breathing, including inspiration and expiration.

What are the two pontine respiratory centers?

Apneustic center and pneumotaxic center.

What does the apneustic center do?

Promotes deep, prolonged inhalation.

What does the pneumotaxic center do?

Limits inhalation and helps the body switch to exhalation.

What happens if the pneumotaxic center is injured?

Inhalation may last too long, causing apneustic breathing.

What happens if both pontine centers are damaged?

Breathing may become very irregular and unpredictable.

How does the cerebral cortex affect breathing?

Allows temporary voluntary control, such as holding your breath.

How do the limbic system, hypothalamus, and amygdala affect breathing?

They change breathing patterns in response to emotions.

What is the blood-brain barrier (BBB)?

A protective filter that controls which substances enter the brain and central nervous system.

Where are central chemoreceptors located?

On the ventrolateral surface of the medulla.

What do central chemoreceptors primarily detect?

Changes in H⁺ in the CSF, mainly caused by changes in CO₂.

Where are peripheral chemoreceptors located?

In the carotid bodies and aortic bodies.

What do peripheral chemoreceptors detect?

Low PaO₂, high PaCO₂, and low arterial pH.

Why may end-stage COPD patients rely more on peripheral chemoreceptors?

Their central response to CO₂ may become less pronounced, increasing the relative contribution of peripheral chemoreceptors.

Should oxygen be withheld from an acutely hypoxemic patient because of COPD?

No. Give needed oxygen and carefully adjust it to the appropriate target.

What is the Hering-Breuer inflation reflex?

Inhibits inspiration when the lungs stretch too much.

What triggers the deflation reflex?

Sudden lung deflation.

What do irritant receptors respond to?

Smoke, dust, and cold air.

Where are J-receptors located?

In the alveolar walls near pulmonary capillaries.

What can J-receptors respond to?

Changes such as fluid buildup in lung tissue, which may cause rapid, shallow breathing.

What is the normal adult ABG pH range?

7.35-7.45.

What is the normal adult PaO₂ range?

Approximately 80-100 mm Hg in a healthy adult at sea level.

What is hypoxemia?

Too little oxygen in arterial blood.

What are the five mechanisms that can cause hypoxemia?

Hypoventilation, diffusion limitation, shunting, V/Q mismatch, and low inspired oxygen.

What does V stand for in V/Q?

Ventilation — air reaching the alveoli.

What does Q stand for in V/Q?

Perfusion — blood reaching the alveolar capillaries.

What is the normal V/Q ratio?

Approximately 0.8.

What does a low V/Q ratio mean?

Not enough ventilation relative to blood flow.

What does a high V/Q ratio mean?

Not enough blood flow relative to ventilation.

What is apneustic breathing?

Deep, prolonged inhalation followed by a short exhalation.

What does ataxic breathing look like?

Irregular, unpredictable breathing that may include pauses.

What can ataxic breathing indicate?

Severe medulla oblongata dysfunction.

What does Cheyne-Stokes breathing look like?

Breathing gradually gets deeper and faster, then shallower and slower, followed by apnea. The cycle repeats.

What does Kussmaul breathing look like?

Deep, rapid, labored breathing.

Why does Kussmaul breathing occur in diabetic ketoacidosis (DKA)?

The body removes more CO₂ to compensate for metabolic acidosis.