Chapter 11 Flashcards
H+ ion production during exercise depends on
exercise intensity
amount of muscle mass involved
duration of exercise
muscle pH vs blood pH
muscle pH decreases more dramatically than blood pH since it is the source of H+ ion production
sources of H+ ions in skeletal muscle
oxidative (aerobic) metabolism of glucose produces carbonic acid to produce H+ ions
non-oxidative (anaerobic metabolism) glycolysis of glucose produces lactate which produces H+ ions
ATP breakdown and release of H+ to increase [H+]
sources of H+ ions during exercise
production of CO2 which is the end product of oxidative phosphorylation
CO2+ H2O = H2CO3= H+ + HCO3-
production of lactic acid: glucose metabolism via glycolysis
Lactic acid = lactate + H+
ATP breakdown results in release of H+
ATP + H2O = ADP + HPO4- + H+
which source of H+ ions produces the most H+
production of CO2
how does increased [H+] impair performance
1) inhibits enzymes in aerobic and anaerobic ATP production which decreases the function of enzymes
2) [H+] can impair muscle contraction by competing with Ca2+ for binding sites on troponin
H+ ions bind to troponin, preventing Ca2+ from binding troponin, which means no conf change in tropomyosin to reveal actin binding sites. myosin can’t bind actin, no crossbridge formation leading to a decrease in force production and a decrease in performance
as work rate increases what happens to HCO3
decreases
as work rate increases what happens to lactate
increases
as work rate increases, what happens to pH
decreases
acid base balance is maintained by
buffers
role of buffers when pH is too high
release H+ ions to decrease pH back to normal
role of buffers when pH is too low
accept H+ ions which makes it more basic increasing pH
what is the first line of defense against a muscle pH shift during exercise
cellular buffer systems
then the blood buffer systems
cellular buffer systems
bicarbonate & phosphates (up to 40% of buffering capacity)
proteins & carnosine (up to 60% of buffering capacity)- work by accepting H+ ions to get rid of H+ ions in the blood stream
transport of H+ out of the muscle
second line of defense against blood pH shift during exercise
blood buffer systems
blood buffer systems
bicarbonate
phosphates
proteins
what are the two H+ ion transporters located within skeletal muscle
NHE
MCT
NHE
H+ ion transporter in skeletal muscle
works by transporting Na+ into muscle and H+ out of muscle
MCT
H+ ion transporter in skeletal muscle
works by taking lactate and H+ out of muscle
what type of muscle fiber has a higher buffering capacity
fast (type 2)
what intensity of exercise can improve muscle buffering capacity and why
high intensity exercise can improve muscle buffering capacity due to increases in carnosine and H+ ion transporters in trained muscle fibers
when pH decreases, what happens to H+ and what happens to bicarb reaction
increases
reaction moves to the left and CO2 is removed by the lungs (via exhalation), eliminating H+ and increasing the pH
what causes VT
increasing blood PCO2 and H+
also increases in blood K+, rising body temp, elevated blood catecholamines, and neural influences may contribute to VT
VT in McArdles patients
evidence from patients with McArdle’s disease indicates that although no lactic acid is produced these individuals do experience a threshold like ventilatory response during incremental exercise
the reason mcardles pts still have VT is due to other metabolic products like H+ and CO2 which stimulate increased ventilation
what happens to arterial PO2 during graded exercise in an untrained subject
is maintained within 10-12 mmHg of resting value
what happens to arterial PCO2 during graded exercise in an untrained subject
slightly decreases with maximal exercise due to hyperventilation
what happens to arterial pH during graded exercise in an untrained subject
decreases with maximal exercise
when above LT, you are producing lots of H+ ions and maxing the buffering system
what happens to ventilation during graded exercise in an untrained subject
linear increase up to 50-75% VO2 max and then an exponential rise
what happens to venous PO2 during graded exercise in an untrained subject
decreases because delivering increased O2 to tissues which allows H+ ions to bind to Hb and change affinity, allowing for more O2 to be delivered to tissues
what organ is important in long term acid base balance at rest
the kidneys
but not significant in acid base balance during exercise because they are too slow and have reduced blood flow during exercise
how do kidneys contribute to acid base balance at rest
by regulating blood bicarb [ ]
when blood pH decreases (increased H+), bicarbonate excretion is reduced
when blood pH increases (decreased H+), bicarb excretion is increased
recent evidence of the removal of lactate following exercise
70% of lactic acid is oxidized meaning it is used as a substrate by heart and skeletal muscle
20% is converted to glucose (via the Cori cycle)
10% is converted to AA
lactic acid is removed more rapidly at what intensity
light exercise in recovery
optimal intensity of recovery exercise is ~30-40% VO2 max
