Chapter 14 Flashcards
how is ventilatory control coordinated?
intricate neural circuits relay information from higher brain centres, the lungs, and other bodily sensors
how is alveolar ventilation coordinated? *
gaseous and chemical states of the blood that bathes the medulla, aortic and carotid artery chemoreceptors pick up information
where does the blood’s chemical state exert the greater control? *
pulmonary ventilation at rest
what are 4 variations that adjust ventilation and maintain arterial blood chemistry?
- arterial PO2
- arterial PCO2
- pH
- temperature
what is the relationship between arterial PO2 and alveolar ventilation?
when arterial PO2 decreases, alveolar ventilation through the aortic and carotid chemoreceptors increase
what is the function of the aortic and carotid chemoreceptors?
protects against reduced oxygen pressure in inspired air
what is the function of peripheral chemoreceptors?
stimulates ventilation during exercise
defends against arterial hypoxia
helps regulate exercise hyperpnea
what is the limiting factor for oxygen consumption during exercise?
delivery of oxygen to the muscles is lacking
how does cortical influence affect ventilatory control?
neural outflow from regions of the motor cortex and cortical activation in anticipation exercise stimulate respiratory neurons in medulla to initiate abrupt increase in ventilation
how does peripheral influence affect ventilatory control?
sensory input from joints, tendons, and muscles influence ventilatory adjustments throughout exercise
what are the 3 ventilation phases during exercise and recovery? *
phase 1
neurogenic stimuli from cerebral cortex and feedback from active limbs stimulate medulla to abruptly increase ventilation
phase 2
after plateau, ventilation rises exponentially to achieve steady state related to metabolic gas exchange demands
phase 3
fine tuning of steady-rate ventilation through peripheral sensory feedback mechanisms
what are 2 factors that impact the decline in ventilation when exercise stops?
- removal of central command drive (desire)
2. decreased sensory input from previously active muscles (mechanoreceptors)
what are 2 factors that slows recovery phase?
- gradual cut of short-term nerve impulse increases of respiratory centre
- reestablishment of body’s normal metabolic, thermal, and chemical environment
what is the aerobic threshold (VT1) and anaerobic threshold (VT2) test?
3 minute stages to achieve steady state
not ideal for maximal testing due to peripheral fatigue
best for graded maximal exercise test to identify anaerobic threshold
what is the VO2 max test?
1 minute stages allow for peak speed/wattage
inappropriate for threshold identification
what are 4 characteristics of aerobic threshold (VT1)? *
RER = 0.92-0.94
increase in FEO2
non-linear increase VE
non-linear increase VCO2
what are 3 characteristics of anaerobic threshold (VT2)? *
RER = 0.98-1.02
decrease in FECO2
non-linear increase in VE
what is steady state?
when the rate of entry into blood is equivalent to the rate of disappearance from blood
what is the lactate threshold 2 (LT)?
highest VO2 or exercise intensity before 1.0 mM increase in blood lactate concentration above pre-exercise level
what does onset of blood lactate accumulation (OBLA) signify?
when blood lactate concentration systematically increases to 4.0 mM
what is the relative intensity (%VO2 max), blood lactate (mmol/L), and heart rate (% max) for aerobic threshold?
70% VO2 max
2.0 (1.0-3.0) mmol/L
75% (70-80%)
what is the relative intensity (%VO2 max), blood lactate (mmol/L), and heart rate (% max) for anaerobic threshold?
85% VO2 max
4.0 (2.5-5.5) mmol/L
85% (80-95%)
what is the relative intensity (%VO2 max), blood lactate (mmol/L), and heart rate (% max) for VO2 max
100% VO2 max
> 10.0 mmol/L
95% (90-100%)
what is maximum lactate steady state (MLSS)?
the highest work rate at which a balance of lactate production and removal exists
blood lactate concentration of no more than 1 mM during final 20 minutes of constant intensity exercise lasting at least 30 minutes
what are 4 factors that impact lactate threshold? *
- capacity of muscle to oxidize pyruvate
- removal at renal and splanchnic removal sites
- capillary density (how vascular)
- reduced O2 content (how hypoxic)
why do we measure lactate threshold? (3) *
- sensitive indicator or aerobic training status
- predicts endurance performance, greater accuracy than VO2 max
- establishes effective training intensity geared to active muscles’ aerobic metabolic dynamics
