W4-L1: Pulmonary Ventilation

Question 1

What regulates pulmonary ventilation?

Answer 1

• Intricate neural circuits relay information from higher brain centers, the lungs, and other bodily “sensors” to coordinate ventilatory control
• The gaseous and chemical states of the blood that bathes the medulla and aortic and carotid artery chemoreceptors that also mediate alveolar ventilation
• These control mechanisms maintain relatively constant alveolar gas pressures throughout a broad range of exercise intensities

Question 2

What Neural Factors control breathing at rest?

3

Answer 2

• Pre-Botzinger Complex (generates rhytmic breathing pattern)
• Dorsal respiratory group (activate diaphragm during inspiration)
• Ventral respiratory group (associated with expiration)

Question 3

What are Humoral Factors affecting breathing?
(peripheral chemoreceptors)

Answer 3

Humoral Factors - Plasma Po2 and Peripheral Chemoreceptors

Peripheral chemoreceptors defend against:

• arterial hypoxia
• pulmonary disease and ascent to higher altitudes,
• and help to regulate exercise hyperpnea

Question 4

edit and seperate into other cards

What are Humoral Factors affecting breathing? Plasma Pco2

2

Answer 4

• At rest, the partial pressure of carbon dioxide (Pco2) in arterial plasma acts as an important stimulus for respiration.
• Even small increases in Pco2 in the air we breathe can cause significant increases in the rate and depth of breathing.

Question 5

What are Humoral Factors affecting breathing? H+ Concentration

Answer 5

• Plasma acidity, which varies with the blood’s CO2 content, exerts strong command over ventilation
• A fall in blood pH signals acidosis and reflects CO2 retention and carbonic acid formation
• As arterial pH declines and H+ accumulate, inspiratory activity increases to eliminate CO2 and reduce arterial levels of carbonic acid

Question 6

The ventilatory responses to hypoxia at three different levels of arterial PCO2

Answer 6

Key Points:
Curves: Each curve represents a different PaCO2 level (38, 45, and 50 torr).

Alveolar Ventilation: As PaO2 increases, alveolar ventilation decreases for a given PaCO2.

PaCO2 Influence: Higher PaCO2 levels (50 torr) correspond to higher alveolar ventilation at a given PaO2 compared to lower PaCO2 levels (38 torr). This indicates that higher carbon dioxide levels stimulate increased ventilation to expel CO2 and intake more oxygen.

Question 7

How is Regulation of Ventilation During Physical Activity chemically controlled?

Answer 7

• Chemical stimulation does not fully account for the increase in ventilation during physical activity
• As exercise intensity increases, alveolar Po2 does not decrease to an extent that increases ventilation through chemoreceptor stimulation
• Pulmonary ventilation during light and moderate exercise closely couples with metabolism and increases proportional to VO2 and VCO2

Question 8

Oxygen Consumption and Partial Pressures of Oxygen and Carbon Dioxide

Alveolar Po2 and Pco2 remain near resting levels throughout a range of exercise intensities, despite large increases in mixed-venous Pco2. Why?

Answer 8

Alveolar Po2 and Pco2 remain near resting levels throughout a range of exercise intensities because of the body’s ability to adjust ventilation to match the increased metabolic demands. Efficient gas exchange, enhanced by increased ventilation and the body’s regulatory mechanisms, allows the maintenance of stable alveolar gas levels despite large increases in mixed-venous Pco2 due to the production of CO2 by the muscles during exercise.

Question 9

What are the 3 phases of Integrated Regulation of Ventilation During Physical Activity?

Answer 9

Ventilation phases during exercise and recovery:

Phase I: Neurogenic stimuli from cerebral cortex and feedback from active limbs stimulate the medulla to abruptly increase ventilation

Phase II: After a brief plateau, ventilation rises exponentially to achieve a steady rate related to metabolic gas exchange demands

Phase III: Fine-tuning of steady-rate ventilation through peripheral sensory feedback mechanisms

Question 10

How is Regulation of Ventilation During Physical activity Neurogenically controlled?

2

Answer 10

1. Cortical influence: anticipation of activity
2. Peripheral influence: Sensory input from joints, tendons and muscle influences the ventilatory adjustments throughout exercise

Question 11

Three Phases of Exercise Hyperpnea

Answer 11

Question 12

What Two factors impact the abrupt decline in ventilation when exercise ceases?

Answer 12

1. Removal of central command drive
2. Decreased sensory input from previously active muscle

Question 13

What does Slower recovery phase result from?

Answer 13

1. Reestablishment of body’s normal metabolic, thermal, and chemical milieu

Question 14

Pulmonary Ventilaioon, Blood Lactate, and VO2 During Graded Exercise to Maximum

Answer 14

know when each reaches point of threshold