Pulmonary Function During Exercise

Question 1

what can cause the partial pressure v. hemoglobin saturation curve to shift to the right?

Answer 1

increased acidity
increased temperature

Question 2

what happens when the partial pressure v. hemoglobin saturation curve shifts to the right?

Answer 2

lower affinity of hemoglobin for oxygen
oxygen offloaded more easily

Question 3

does myoglobin release oxygen easily at high concentrations of oxygen?

Answer 3

no

Question 4

when is myoglobin important?

Answer 4

transporting oxygen to the mitochondria at the beginning of exercise and during very strenuous exercise

Question 5

what happens to PaCO2, PaO2, and pH during strenuous exercise in most animals?

Answer 5

remain normal

Question 6

what enzyme allows the interconversion of bicarbonate and CO2?

Answer 6

carbonic anhydrase

Question 7

what determines ventilatory control?

Answer 7

input from respiratory center in medulla
chemical state of blood as it communicates with medulla
plasma PaO2, PaCO2, H+ concentrations
chemoreceptors

Question 8

where are the sensors of PaO2?

Answer 8

aortic bodies at arch of aorta
carotid bodies at branching of carotid arteries

Question 9

what is the most important stimulus to ventilation?

Answer 9

partial pressure of CO2 in plasma

Question 10

why does ventilation increase in exercise out of proportion to PaCO2?

Answer 10

cortical input
peripheral input from mechanoreceptors

Question 11

what happens during steady rate, aerobic exercise, with ventilation and oxygen uptake?

Answer 11

ventilation increases as oxygen uptake does

Question 12

what happens when exercise intensity increases?

Answer 12

eventually, tissue demand outstrips the combined respiratory and cardiovascular ability to supply oxygen
anaerobic component, lactate and tissue CO2 rise

Question 13

what does VO2 refer to?

Answer 13

amount of oxygen an individual can take up at any given time

Question 14

where does blood go preferentially in the lungs of a horse?

Answer 14

dorsal regions

Question 15

what do horses have that is unprecedented?

Answer 15

pulmonary hypertension
reaches close to 100mmHg at a gallop

Question 16

what are the five basic mechanisms of hypoxemia?

Answer 16

decrease in inspired FiO2
right to left shunts
V/Q mismatching
diffusion impairment
alveolar hypoventilation

Question 17

why do horses experience hypoxia and hypercapnea during exercise?

Answer 17

hypoventilate
diffusion impairment

Question 18

when does the precipitously steep portion of the oxygen-hemoglobin binding curve occur?

Answer 18

PaO2 of 60mmHg

Question 19

if we breathe in a gas with a higher percentage of O2, what happens to our minute ventilation?

Answer 19

slows down

Question 20

why do we breathe with a greater rate during exercise?

Answer 20

greater minute ventilation
likely dissipates heat

Question 21

what increases in the CSF when CO2 is increased?

Answer 21

H+

Question 22

what does the ventilatory equivalent for oxygen tell us?

Answer 22

efficiency of ventilation: how many liters of air for every liter of oxygen you consume

Question 23

what contributes most to VO2max?

Answer 23

heart
capillarization of muscle
density of mitochondria
not respiratory system

Question 24

when does breathing frequency and stride frequency become tightly coupled in horses?

Answer 24

canter
gallop
not walk/trot

Question 25

what does lack of stride/breath coupling indicate in a horse?

Answer 25

respiratory disease

Question 26

what might cause pulmonary hypertension in horses?

Answer 26

high left atrial pressures

Question 27

what is inertance?

Answer 27

impedance to breathing that moving a column of air back and forth at increasing frequencies entails

Question 28

what happens with resistance when a horse exercises?

Answer 28

it increases

Question 29

how much does the work of breathing increase in a horse between rest and exercise?

Answer 29

almost 500-fold

Question 30

what does it mean that horses’ work of breathing increases so much during exercise?

Answer 30

they may reach a point where increases in ventilation cost more in energy than the horse can afford while still performing mechanical work