Chapter 11: Acid-Base Balance During Exercise Flashcards
3 factors that H+ production depends on
1) exercise intensity
2) amount of muscle mass involved
3) duration of exercise
how does the decline in blood pH compare to the decline in muscle pH?
muscle pH declines more dramatically than blood pH
3 source of H+ ions during exercise
1) production of CO2
2) production of lactic acid
3) ATP breakdown
where does carbon dioxide come from?
end product of oxidative phosphorylation (bicarbonate buffering reaction contributes the H+ ions with an increase in CO2)
where does lactic acid come from?
glucose metabolism via glycolysis; lactic acid <—> lactate + H+
how does ATP production result in H+ increase?
ATP + H2O <—> ADP + HPO4- + H+
what types of sports/exercises promote acid-base disturbances in skeletal muscle?
higher intensity exercises lasting greater than 45 seconds (linked to effort/max effort)
2 ways increased [H+] impairs performance
1) inhibits enzymes in aerobic and anaerobic ATP production
2) [H+] can impair muscle contraction by competing with Ca2+ for binding sites on troponin
how is the acid-base balance maintained during exercise?
by buffers that releases H+ ions when pH is too high and accepts H+ ions when pH is too low
5 cellular buffer systems (first line of defense against pH changes)
1) bicarbonate *
2) phosphates *
3) proteins
4) carnosine
5) transport of hydrogen ions out of muscle
which have a higher buffering capacity: type I or type II?
type II muscle fibers have a higher buffering capacity
how does high intensity exercise training improve the muscle buffering capacity?
by increasing carnosine and hydrogen ion transporters in the trained muscle fibers
2 blood buffer systems (second line of defense against changes in pH)
1) respiratory compensation for metabolic acidosis
2) bicarbonate
given the bicarb buffering equation:
CO2 + H2O <—> H2CO3 <—> H+ + HCO3-
how does decreasing pH lead to CO2 removal by lungs?
decreased pH (increased H+ ions) —> reaction moves to the left —> CO2 is removed by the lungs —> eliminating H+ and increasing pH
what is ventilatory threshold caused by?
increasing blood PCO2 and H+ (increasing K+, increasing body temp, elevated blood catecholamines and neural influences may contribute as well)
