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anticipatory response
HR increases above resting levels just before the start of exercise
what are the effects of catecholmines during exercise?
increase Ca2+ release leading to increased contractility
increased HR leading to opening of Na+ channels
increased BP
increased systemic vasoconstriction
increased ventilation
how does heart rate increase?
proportional to exercise
maximum heart rate
highest heart rate achieved in an all out effort
Stroke volume plateaus at ~40-60% of VO2 max in normal individuals, why?
The short time spent in diastole decreases stroke volume because we don’t have enough time to fill the heart with blood
3 factors that increase stroke volume
increased preload
increased contractility
decreased afterload
Preload
(AKA venous return) end diastolic ventricular stretch
Frank-starling mechanism
increased stretch (causing increased EDV) causes increased contraction strength
contractility
inherent ventricle property caused by levels of catecholamines
afterload
aortic resistance
max cardiac output (Q)
function of body size and aerobic fitness
how does systolic pressure increase with exercise
due to increased contractility, this pressure increases linearly with increasing exercise intensity
how does diastolic pressure increase with exercise
it does not change substantially with increasing exercise intensity
how does MAP increase with exercise
due to total peripheral resistance decrease & Q increase, this pressure increases linearly with increasing exercise intensity
valsalva maneuver
technique where person tries to exhale while the mouth, nose, and glottis are closed
how is blood flow redistribution sensed?
chemoreceptors —> sensing for O2, CO2, lactic acid, H+, etc
what situations might limit blood flow to muscles during exercise?
atherosclerosis
anemia
eating too much
hot temperatures
dehydration
cardiovascular drift
the gradual increase in heart rate and decrease in stroke volume that occurs during prolonged exercise, especially in hot conditions. This happens as the body redirects blood to the skin for cooling, leading to reduced blood volume available for the heart to pump. As a result, the heart compensates by beating faster to maintain cardiac output, even though stroke volume declines.
(a-v)O2 difference
amount of oxygen extracted from the blood as it travels through the body. Increases with exercise intensity
what is the ventilatory response to exercise?
increased ventilation before muscle contractions as an anticipatory response
gradual increased ventilation throughout exercise
delay return to baseline once exercise is finished
what 2 factors make up pulmonary ventilation?
tidal volume
frequency
tidal volume
the amount of air that moves in and out of the lungs during a breath
ventilatory threshold
the point during exercise at which breathing rate increases disproportionately to oxygen consumption. This occurs as the body shifts from primarily aerobic metabolism to greater reliance on anaerobic metabolism, leading to increased production of carbon dioxide and lactic acid. To compensate, ventilation rises rapidly to expel excess CO₂ and maintain acid-base balance. This threshold is often used as an indicator of endurance performance and aerobic fitness.
lactate threshold
the point at which blood lactate concentration increases substantially
