Chapter 11

Question 1

H+ ion production during exercise depends on

Answer 1

exercise intensity
amount of muscle mass involved
duration of exercise

Question 2

muscle pH vs blood pH

Answer 2

muscle pH decreases more dramatically than blood pH since it is the source of H+ ion production

Question 3

sources of H+ ions in skeletal muscle

Answer 3

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+]

Question 4

sources of H+ ions during exercise

Answer 4

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+

Question 5

which source of H+ ions produces the most H+

Answer 5

production of CO2

Question 6

how does increased [H+] impair performance

Answer 6

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

Question 7

as work rate increases what happens to HCO3

Answer 7

decreases

Question 8

as work rate increases what happens to lactate

Answer 8

increases

Question 9

as work rate increases, what happens to pH

Answer 9

decreases

Question 10

acid base balance is maintained by

Answer 10

buffers

Question 11

role of buffers when pH is too high

Answer 11

release H+ ions to decrease pH back to normal

Question 12

role of buffers when pH is too low

Answer 12

accept H+ ions which makes it more basic increasing pH

Question 13

what is the first line of defense against a muscle pH shift during exercise

Answer 13

cellular buffer systems

then the blood buffer systems

Question 14

cellular buffer systems

Answer 14

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

Question 15

second line of defense against blood pH shift during exercise

Answer 15

blood buffer systems

Question 16

blood buffer systems

Answer 16

bicarbonate
phosphates
proteins

Question 17

what are the two H+ ion transporters located within skeletal muscle

Answer 17

NHE
MCT

Question 18

NHE

Answer 18

H+ ion transporter in skeletal muscle

works by transporting Na+ into muscle and H+ out of muscle

Question 19

MCT

Answer 19

H+ ion transporter in skeletal muscle

works by taking lactate and H+ out of muscle

Question 20

what type of muscle fiber has a higher buffering capacity

Answer 20

fast (type 2)

Question 21

what intensity of exercise can improve muscle buffering capacity and why

Answer 21

high intensity exercise can improve muscle buffering capacity due to increases in carnosine and H+ ion transporters in trained muscle fibers

Question 22

when pH decreases, what happens to H+ and what happens to bicarb reaction

Answer 22

increases
reaction moves to the left and CO2 is removed by the lungs (via exhalation), eliminating H+ and increasing the pH

Question 23

what causes VT

Answer 23

increasing blood PCO2 and H+
also increases in blood K+, rising body temp, elevated blood catecholamines, and neural influences may contribute to VT

Question 24

VT in McArdles patients

Answer 24

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

Question 25

what happens to arterial PO2 during graded exercise in an untrained subject

Answer 25

is maintained within 10-12 mmHg of resting value

Question 26

what happens to arterial PCO2 during graded exercise in an untrained subject

Answer 26

slightly decreases with maximal exercise due to hyperventilation

Question 27

what happens to arterial pH during graded exercise in an untrained subject

Answer 27

decreases with maximal exercise
when above LT, you are producing lots of H+ ions and maxing the buffering system

Question 28

what happens to ventilation during graded exercise in an untrained subject

Answer 28

linear increase up to 50-75% VO2 max and then an exponential rise

Question 29

what happens to venous PO2 during graded exercise in an untrained subject

Answer 29

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

Question 30

what organ is important in long term acid base balance at rest

Answer 30

the kidneys

but not significant in acid base balance during exercise because they are too slow and have reduced blood flow during exercise

Question 31

how do kidneys contribute to acid base balance at rest

Answer 31

by regulating blood bicarb [ ]

when blood pH decreases (increased H+), bicarbonate excretion is reduced
when blood pH increases (decreased H+), bicarb excretion is increased

Question 32

recent evidence of the removal of lactate following exercise

Answer 32

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

Question 33

lactic acid is removed more rapidly at what intensity

Answer 33

light exercise in recovery

optimal intensity of recovery exercise is ~30-40% VO2 max