Chapter 10: Respiration During Exercise Flashcards by Anna Stone

what is the difference between pulmonary respiration and cellular respiration?

pulmonary ventilation (breathing): exchange of O2 and CO2 in the lungs
cellular respiration: O2 utilization and CO2 production by the tissues

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purposes of the respiratory system during exercise

1) gas exchange between the environment and the body
2) regulation of acid-base balance during exercise

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how does intrapulmonary pressure and atmospheric pressure compare during inspiration and expiration, respectively?

inspiration: intrapulmonary pressure < atmospheric
expiration: intrapulmonary pressure > atmospheric

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how does the diaphragm and the volume of the lungs change during inspiration and expiration, respectively?

inspiration: diaphragm pushes downward, ribs lift outwards and the volume of the lungs increases
expiration: diaphragm relaxes, ribs pull downward and the volume of the lungs decreases

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what is pulmonary ventilation (minute ventilation, Ve, V, MV)?

the amount of air moved in or out of the lungs per minute (L/min)

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2 factors determining minute ventilation. equation?

tidal volume (Vt): amount of air moved per breath (L/breath)
breathing frequency (f): number breaths per minutes (breath/min)
Ve = Vt x f

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pulmonary ventilation during rest and during maximal exercise?

rest = 7.5 L/min
max exercise = 120-175 L/min

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breathing frequency at rest and at maximal exercise?

rest = 15 breaths/min
max exercise = 40-50 breaths/min

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tidal volume at rest and during maximal exercise?

rest = 0.5 L/breath
max exercise = 3-3.5 L/breath

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how is ventilation controlled at rest?

somatic motor neurons in the spinal cord and the respiratory control center in the medulla oblongata

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2 inputs to the respiratory control center

neural input and humoral chemoreceptors

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what is the neural input that is sent to the respiratory control center?

from motor cortex and skeletal muscle mechanoreceptors (stimulate muscle spindles, Golgi tendon organs, joint pressure receptors —> input to the RCC —> increased ventilation)

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2 humoral chemoreceptors and their locations

central chemoreceptors: medulla
peripheral chemoreceptors: aortic and carotid bodies

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what do central chemoreceptors detect change in?

PCO2 and H+ concentration in cerebral spinal fluid

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what do peripheral chemoreceptors detect change in?

PO2, PCO2, H+, and K+ in the blood

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primary mediator of ventilation during submaximal exercise

neural input

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primary mediator of ventilation during maximal exercise?

humoral input

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describe the pattern of blood flow in pulmonary circulation

pulmonary artery receives mixed venous blood from the right ventricle —> oxygenated blood is returned to the left atrium via pulmonary vein

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rate of blood flow in pulmonary circuit is equal to __

rate of blood flow in the systemic circuit

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during resting conditions (standing), where does most of the blood flow specifically go in the lungs? why?

base of the lung due to gravitational force

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during upright exercise conditions, where in the lung does bloodflow increase?

blood flow increases to all parts of the lung; top of the lung (apex)

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what does the ventilation/perfusion ratio (V/Q) indicate? ideal value?

if the rate of blood flow is matching ventilation
ideal: ~1.0 or above if blood flow is high

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how does the V/Q compare at the apex and base of the lungs?

apex: (ventilation > blood flow) so underperfused relative to ventilation
base: (ventilation < blood flow) so overperfused relative to ventilation

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what is exercise-induced asthma (bronchoconstriction) caused by?

contraction of smooth muscle around the airways (bronchospasms) and mucus in the airways during or after exercise

symptoms of exercise-induced asthma

labored breathing (dyspnea), wheezing sound

how common is exercise-induced asthma in elite athletes?

>10% of elite athletes, but doesn’t impair performance if correctly managed

describe how asthma affects the V/Q ratio

initially, there is reduced alveolar ventilation and excessive perfusion —> V/Q <1 —> decreased PO2 and increased PCO2 in the alveoli —> pulmonary arterioles serving these alveoli constrict —> reduced alveolar ventilation, reduced perfusion

describe how a blood clot affects the V/Q ratio

initially, there is enhanced alveolar ventilation and inadequate perfusion —> V/Q > 1 —> pulmonary arterioles serving these alveoli dilate —> enhanced alveolar ventilation and enhanced perfusion

how does low to moderate intensity exercise affect V/Q ?

improves V/Q

how does high intensity exercise affect V/Q? why?

results in slight V/Q inequality pulmonary capillary transit time: blood is moving through the capillary too quickly to fully saturate with oxygen

99% of O2 transported in the blood is bound to ___

hemoglobin

3 factors that determine how much O2 can be transported per unit of blood

1) Hb concentration 2) arterial oxygen saturation 3) amount dissolved in the plasma (minor contribution)

the direction of the following rxn depends on what 2 factors: deoxyhemoglobin + O2 —> oxyhemoglobin

1) PO2 of the blood 2) affinity between Hb and O2

what happens to oxyhemoglobin association/ dissociation at the lung?

high PO2 —> formation of oxyhemoglobin (“loading”)

what happens to oxyhemoglobin dissociation/association at the tissues (eg skeletal muscles)?

low PO2 —> release of O2 to tissues (“unloading”)

how does pH affect the O2-Hb dissociation curve?

decreased pH (more H+ ions) lowers Hb-O2 affinity which results in a rightward shift of the curve & favors “offloading” of O2 to the tissues

how does temperature affect the O2-Hb dissociation curve?

increased blood temperature lowers Hb-O2 affinity, which results in a “rightward” shift of the curve

what is 2-3 DPG?

byproduct of RBC glycolysis

how does 2-3 DPG affect the O2-Hb dissociation curve?

results in a rightward shift of the curve (during altitude exposure, not a major cause of rightward shift during exercise)

mechanism of pH affecting O2-Hb dissociation curve

intense exercise —> increased blood H+ —> H+ ions bind to Hb —> reduces Hb capacity to transport O2

mechanism of temperature affecting the O2-Hb dissociation curve

body temp increases during exercise —> increased temp weakens the bond between O2 and Hb —> assists unloading of O2 to working muscle

how does arterial and venous O2 content change during exercise?

arterial O2 content remains relatively unchanged, (a-v)O2 diff at the tissues increases, so then venous O2 content decreases

purpose of myoglobin

shuttles O2 from the cell membrane to the mitochondria of skeletal and cardiac muscle fibers

how does myoglobin content vary in type I and type IIx fibers?

Mb content high in type I and low in type IIx

which has a higher affinity for O2: hemoglobin or myoglobin? why?

myoglobin, this is important because it “takes” the O2 from Hb at the blood where PO2 is lower

how does myoglobin contribute to oxygen deficit and EPOC?

during oxygen deficit: myoglobin O2 stores serve as an “O2 reserve” during transition periods from rest to exercise during EPOC: O2 consumption is above rest in order to replenish the myoglobin O2 stores

3 ways CO2 is transported in the blood

1) 10% dissolved CO2 in plasma 2) 20% bound to Hb 3) 70% as bicarbonate

how does pulmonary ventilation remove H+ from the blood?

via the bicarbonate buffering reaction

how does increased ventilation affect CO2 concentration?

increased ventilation results in CO2 exhalation —> reduces PCO2 and H+ concentration —> pH increases

how does decreased ventilation affect CO2 concentration?

decreased ventilation results in buildup of CO2 —> increases PCO2 and H+ concentration —> pH decrease

how do PO2 and PCO2 change during steady state exercise?

remain relatively unchanged

how does ventilation change from onset of exercise to steady state?

ventilation increases rapidly then there is a slower rise towards steady state

how do ventilation and blood gases change during prolonged exercise in hot environments?

little change in PCO2; ventilation tends to drift upward

why does ventilation increase during prolonged exercise in a hot environment if PCO2 isn’t changing?

increased blood temperature affects respiratory control center

how does ventilation change during graded exercise?

ventilation increases steadily until the ventilatory threshold is reached where ventilation begins to increase exponentially

is the pulmonary system seen as a limitation during submaximal exercise?

when might the pulmonary system be seen as a limitation during exercise?

in highly trained elite endurance athletes during graded, maximal exercise

why might the pulmonary system limit performance in elite athletes at max exercise?

mechanical limitations of the lung & respiratory muscles fatigue during prolonged (>120 mins), high intensity (90-100% max) exercise

how common is exercise-induced arterial hypoxemia? why does it occur?

40-50% of elite athletes; blood is moving too quickly past the lungs to be able to fully saturate with oxygen in the capillaries