Chapter 10: Respiration During Exercise Flashcards
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
purposes of the respiratory system during exercise
1) gas exchange between the environment and the body
2) regulation of acid-base balance during exercise
how does intrapulmonary pressure and atmospheric pressure compare during inspiration and expiration, respectively?
inspiration: intrapulmonary pressure < atmospheric
expiration: intrapulmonary pressure > atmospheric
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
what is pulmonary ventilation (minute ventilation, Ve, V, MV)?
the amount of air moved in or out of the lungs per minute (L/min)
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
pulmonary ventilation during rest and during maximal exercise?
rest = 7.5 L/min
max exercise = 120-175 L/min
breathing frequency at rest and at maximal exercise?
rest = 15 breaths/min
max exercise = 40-50 breaths/min
tidal volume at rest and during maximal exercise?
rest = 0.5 L/breath
max exercise = 3-3.5 L/breath
how is ventilation controlled at rest?
somatic motor neurons in the spinal cord and the respiratory control center in the medulla oblongata
2 inputs to the respiratory control center
neural input and humoral chemoreceptors
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)
2 humoral chemoreceptors and their locations
central chemoreceptors: medulla
peripheral chemoreceptors: aortic and carotid bodies
what do central chemoreceptors detect change in?
PCO2 and H+ concentration in cerebral spinal fluid
what do peripheral chemoreceptors detect change in?
PO2, PCO2, H+, and K+ in the blood
primary mediator of ventilation during submaximal exercise
neural input
primary mediator of ventilation during maximal exercise?
humoral input
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
rate of blood flow in pulmonary circuit is equal to __
rate of blood flow in the systemic circuit
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
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)
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
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
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?
no
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
