Control of Breathing

Question 1

What are the main components of the respiratory system?

Answer 1

The respiratory system includes the nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.

Question 2

What is the primary function of the respiratory system?

Answer 2

The respiratory system’s primary function is gas exchange—the intake of oxygen (O2) and removal of carbon dioxide (CO2).

Question 3

What controls breathing at the central level?

Answer 3

Breathing is controlled by the medulla oblongata and pons in the brainstem, which regulate the rate and depth of breathing.

Question 4

What role do peripheral chemoreceptors play in breathing?

Answer 4

Peripheral chemoreceptors, located in the carotid and aortic bodies, monitor changes in blood oxygen (O2), carbon dioxide (CO2), and pH.

Question 5

What is hypoxia?

Answer 5

Hypoxia refers to a deficiency in the amount of oxygen reaching tissues.

Question 6

What is hypercapnia?

Answer 6

Hypercapnia is an excessive amount of carbon dioxide in the bloodstream, often caused by inadequate respiration.

Question 7

How is breathing initiated?

Answer 7

Breathing is initiated by rhythmic impulses from the respiratory centers in the medulla and pons, which send signals to the respiratory muscles.

Question 8

What is the function of the dorsal respiratory group (DRG)?

Answer 8

The DRG integrates sensory input from chemoreceptors and regulates the inspiratory muscles during quiet breathing.

Question 9

What is the function of the ventral respiratory group (VRG)?

Answer 9

The VRG controls forced expiration and active inspiration during exercise or distress.

Question 10

What is the role of the pneumotaxic center?

Answer 10

The pneumotaxic center in the pons helps coordinate the transition between inspiration and expiration by limiting inspiration duration.

Question 11

What inputs modify respiratory rhythms?

Answer 11

Respiratory rhythms are modified by higher brain centers, such as the cerebral cortex (voluntary control) and the hypothalamus (emotional changes).

Question 11

What is the role of the apneustic center?

Answer 11

The apneustic center stimulates the inspiratory neurons to prolong inspiration and delay expiration.

Question 12

How do baroreceptors, thermoreceptors, and mechanoreceptors influence breathing?

Answer 12

These receptors provide feedback on blood pressure, temperature, and lung stretch, influencing respiratory rate and depth.

Question 13

What is the primary stimulus for central chemoreceptors?

Answer 13

Central chemoreceptors, located in the medulla, are primarily sensitive to changes in PaCO2 (carbon dioxide levels) and pH in cerebrospinal fluid (CSF).

Question 14

How do peripheral chemoreceptors respond to hypoxia?

Answer 14

Peripheral chemoreceptors in the carotid and aortic bodies respond to low PaO2 by increasing their firing rate, stimulating ventilation.

Question 15

What is the relationship between PaCO2, PaO2, and ventilation?

Answer 15

An increase in PaCO2 strongly stimulates ventilation, while a significant decrease in PaO2 enhances the response, creating a synergistic effect.

Question 16

How do central chemoreceptors respond to changes in CSF pH?

Answer 16

Central chemoreceptors detect changes in CSF pH, reflecting changes in PaCO2, and adjust breathing to maintain stable levels of CO2.

Question 17

What is the role of the ventral respiratory group (VRG) during exercise?

Answer 17

During exercise, the VRG becomes active, increasing both inspiratory and expiratory muscle activity to meet the body’s higher oxygen demands.

Question 18

How does the dorsal respiratory group (DRG) receive input?

Answer 18

The DRG receives sensory input from the IXth (glossopharyngeal) and Xth (vagus) cranial nerves and adjusts the breathing rhythm accordingly.

Question 19

What happens to ventilation during emotional stress?

Answer 19

Emotional stress activates the hypothalamus and limbic system, causing changes in breathing rate and depth, often leading to hyperventilation or breath-holding.

Question 20

What effect does oxygen therapy have on patients with chronic hypercapnia?

Answer 20

In patients with chronic hypercapnia, high levels of O2 can depress the carotid body’s hypoxic drive, potentially causing dangerous hypoventilation.

Question 20

How does chronic hypercapnia affect chemoreceptor sensitivity?

Answer 20

In chronic hypercapnia, chemoreceptors adapt by reducing their sensitivity to elevated CO2, leading to reliance on hypoxia for ventilation control.

Question 21

How do the carotid bodies respond to changes in PaO2?

Answer 21

The carotid bodies respond to dramatic decreases in PaO2 by increasing ventilation, but they are less sensitive to changes in oxygen content.

Question 21

What is the primary response of central chemoreceptors to hypercapnia?

Answer 21

Central chemoreceptors strongly stimulate ventilation when PaCO2 increases, producing about 80% of the ventilatory response to rising CO2.

Question 22

What is the function of type I (glomus) cells in the carotid bodies?

Answer 22

Type I (glomus) cells are the chemosensitive cells in the carotid bodies that detect changes in blood gases and initiate reflexive changes in ventilation.

Question 23

How does hypercapnia influence ventilation compared to hypoxia?

Answer 23

Hypercapnia is more effective at stimulating ventilation than hypoxia, but both together have a synergistic effect on respiratory drive.

Question 24

What is the negative feedback loop for CO2 regulation?

Answer 24

Increased PaCO2 stimulates chemoreceptors, leading to increased respiratory muscle contraction, which lowers PaCO2, restoring normal levels.

Question 25

How does PaCO2 influence minute ventilation?

Answer 25

For every 1mmHg rise in PaCO2, minute ventilation increases by 2-3L/min to eliminate excess CO2 and restore homeostasis.

Question 26

Why are central chemoreceptors insensitive to hypoxia?

Answer 26

Central chemoreceptors primarily respond to CO2 and pH changes, with little response to low oxygen levels (hypoxia), which is detected mainly by peripheral chemoreceptors.

Question 27

What happens during CO2 narcosis?

Answer 27

In CO2 narcosis, excessive oxygen in a chronically hypercapnic patient depresses their hypoxic drive, leading to respiratory depression, increased PaCO2, and potential coma.