Pulmonary Ventilation Regulation

Question 1

pulmonary ventilation

Answer 1

the need for different levels of respiration varies with the physiologic state of an individual
the role of the respiratory system is to maintain constant levels of oxygen, carbon dioxide, and H+ in arterial blood
negative feedback system
changes in the levels of O2, CO2, and H+ in the blood cause compensatory changes in the level of ventilation

Question 2

breathing

Answer 2

an automatic process triggered in the brain stem
automatic cycle of breathing can be modified or even temporarily stopped, depending on the information received by the respiratory control center

Question 3

respiratory center

Answer 3

located in the medulla and pons
inspiration and expiration controlled by inspiratory and expiratory neurons

Question 4

pons

Answer 4

controls the rate and pattern of breathing as well as promotes inhalation by a constant stimulation of the neurons in the medulla

Question 5

medulla

Answer 5

governs the normal respiratory cycle

Question 6

chemoreceptors

Answer 6

sensitive to changes in mostly O2 as well as CO2 and pH

Question 7

central chemoreceptors

Answer 7

neurons located in the medulla that are sensitive to pCO2 and pH

Question 8

peripheral (arterial) chemoreceptors

Answer 8

neuron bodies positioned in the carotid and aortic arteries that detect arterial hypoxia and initiate a ventilatory response in the medulla

Question 9

muscle and lung receptors

Answer 9

muscle spindles and mechanoreceptors

Question 10

muscle spindles

Answer 10

detects, responds to, and modulates changes in the length of the muscle fiber

Question 11

mechanoreceptors

Answer 11

monitor the expansion of the lung, the size of the airway, the force of respiratory muscle contraction, and the extent of muscle shortening

Question 12

no single mechanism entirely accounts for the increase in ventilation (hypernea) during exercise

Answer 12

phase I: first 20 seconds of exercise
central command input
feedback proprioceptors in joints and active skeletal muscle
phase II: exponential rise in ventilation to achieve steady state based on metabolic gas exchange demands
central command input
feedback from respiratory neurons and chemoreceptors
feedback proprioceptors in joints and active skeletal muscle
phase III: fine tuning in steady-state ventilation
central and reflex stimuli from carbon dioxide and H+ concentrations

Question 13

during light and moderate intensity exercise

Answer 13

ventilation increase linearly with oxygen consumption and carbon dioxide production
carbon dioxide is transported as bicarbonate
alveolar PO2 and PCO2 remain near resting levels
lactate production equals lactate disappearance
transit time remains long enough for complete equilibrium of lung-blood gases

Question 14

vigorous exercise

Answer 14

pulmonary ventilation is no longer linked tightly to oxygen consumption
strenuous exercise results in increased ventilation
small increase in PCO2 cause large increases in vigorous exercise
acidosis causes an increase in carbon dioxide
1. CO2 and H+ produced exceeding the capacity of hemoglobin accepting H+ which increases carbonic acid
2. CO2 and H+ produced as a byproduct of lactic acid being buffered by the sodium bicarbonate system

Question 15

ventilatory threshold

Answer 15

the point where pulmonary ventilation increases disproportionately relative to increases in oxygen consumption
considered the threshold for anaerobic metabolism

Question 16

hyperventilation

Answer 16

a result of carbon dioxide’s production exceeding oxygen consumption
VCO2/VO2 > 1.00
reduces alveolar and arterial PCO2 and increases alveolar PO2 from resting level
creates a greater diffusion gradient

Question 17

pulmonary diffusing capacity

Answer 17

at rest and during light to moderate exercise transit time remains long enough for complete equilibrium of lung-blood gases
limits VO2 max in elite, highly trained endurance athletes

Question 18

exercise-induced hypoxemia

Answer 18

a decrease in partial pressure of arterial PO2 below 75 mmHg
pulmonary capillary blood flow transit time is too fast for diffusion to allow for adequate hemoglobin saturation
due to high cardiac output found in trained athletes