Mod 4: Respiratory Function and Regulation During Exercise Flashcards
what’s the difference between internal and external respiration?
External respiration, also known as breathing, involves both bringing air into the lungs (inhalation) and releasing air to the atmosphere (exhalation). During internal respiration, oxygen and carbon dioxide are exchanged between the cells and blood vessels.
describe the different lung volume measurements and how they are influenced by exercise
Spirometry
explain how respiratory rate(AKA ventilation rate) changes during exercise(going from rest to exercise)
increases
air movement into and out of lungs
pulmonary ventilation (external resp)
gas exchange between lungs and the blood
pulmonary diffusion(external resp)
movement of O2 and CO2 via the blood
Gas Transport(internal resp)
gas exchange between capillary blood and the tissues
Capillary diffusion (internal resp)
air moved with each breath
-amount of air entering and leaving the lungs with each normal breath
Tidal volume (VT)
500ml
fresh air which actually reaches alveoli
VT-“dead space volume” (VD
-not all tidal volume reaches alveoli
Alveolar Volume (VA)
the greatest amount of air that can be expired after a maximal inspiration
vital capacity (VC)
the sum of the vital capacity and the residual volume
total lung capacity (TLC)
the volume of air remaining in the lungs after normal expiration
functional residual capacity
the amount of air remaining in the lungs after maximal expiration
residual volume(RV)
normal individual expiration (total lung capacity)
6-8 L
ventilation rate
(per unit of time) depends on tidal volume and respiratory rate(breathing frequency)
what are ventilation rates at rest
minute ventilation (VI or VE) -VT x RR
=500 ml x 12 breaths/min
=6000ml/min (total air flow each min)
BUT NOT ALL OF THAT AIR IS USED
need to subtract dead space volume(can be influenced by smoking)
Alveolar Ventilation VA
= VA x f
=(VT-VD) x RR
(500-150(dead space)) x 12 breaths/min
= 4200 ml/min –> fresh air flow each min
if u have lots of dead space and want to keep alveolar ventilation the same u need to: increase tidal volume or increase breathing frequency
ventilation rate at maximal exercise for avg untrained male
minute and alveolar ventilation
minute ventilation
VI = VT x RR
=3000ml x 40 breaths/min
=120L/min (20x HIGHER THAN REST)
alveolar ventilation
VA=VA x RR
=(VT-VD) x f(RR)
=(3000-175ml) x 40b/min
=113L/min is alveolar ventilation–>27 X higher than rest–> acc getting to alveoli after accounting for dead space
-dead space increases during max exercise but is offset by big tidal volume so not a big issue
what are the factors that determine gas exchange
- Partial pressure gradient across the barrier(alveoli has capillaries surrounding it, in between there’s a barrier)
high–> low pressure, pressure gradient across barrier -
diffusion capacity (solubility of a gas)
low solubility=high partial pressure across barrier to get across
high solubility=dont need big pressure gradient to get across -
characteristics of the barrier
-thin, 1 cell thick
how is partial pressure of a gas calculated? why is it important?
what are the changed that happen in PO2 and PCO2 in the body-what are the normative(avg) values?
gas exchange pathway between alveoli and capillaries
inspired air path: bronchial tree–> alveoli
blood path: right ventricle–> pulmonary arteries–> pulmonary capillaries
-alveoli surrounded by capillaries
what are the 2 main functions of gas exchange
- replenish blood oxygen supply
- removes co2 from blood
portion of total pressure due to presence of a single gas
Pa (2 atm) + Pb (1atm) = Ptotal(3 atm)
partial pressure
what is the P O2 in dry atmospheric air at sea level?
given: fraction of O2 :0.2093
pressure of atmospheric air: 760 mmHg
=fraction x total pressure
=0.2093 x 760 mm Hg
=159 mmHg
what happens to air pressure as altitude increases
lower pressure
-closer to earth , PP of gases is higher
what’s the effect of water vapor(humidity) on gas pressure?
where does it happen in the body?
water molecules disperse gas molecules
=increase total volume of air (water + gas)
=decrease gas pressure for given volume of air
INVERSE RELATIONSHIP: water enters air, gas molecules spread out, volume of air increases, pressure decreases
-happens in trachea
what is the Pressure of Oxygen (PO2) in dry atmospheric air vs in tracheal air? WHY
Dry atmospheric air: 159 atm
tracheal air: 149 atm
pressure decreased in trachea bc water molecules got into gas, increasing volume, decreasing pressure
what happens to PO2 as oxygen travels throughout the body?
from atmosphere–> trachea–> alveoli–> tissue cell—> venous blood
- atomsphere : starting PO2
- Trachea: small dec Pressure due to water vapour and inc volume
-
Alveoli: LARGE DECEASE in pre
ssure due to mixing with venous blood (deox blood returning to lungs) -
Arterial blood: small decrease in pressure, similar to alveoli–> DETERMINES O2 bound to hemoglobin
pp of o2 in arterial blood determines ho much blood is bound to hemoglobin, which determines amount/content of oxygen actually in the blood stream to get to working muscles - Tissue Cell: LARGEST DEC in pressure, relative to O2 used in muscle, during exercise use more O2 than at rest, so LARGER drop during exercise than at rest
- Venous Blood: Depends on muscle tissue O2 use (O2 leftover), larger drop in PP(as low as 5) during exercise than at rest
** In this system rest, start with PO2=105, PCO2=40, end with PO2=40, PCO2=46**
** Heavy exercise: end with PO2=25, PCO2=60**
CO2 is more soluble, so it can diffuse finw w gradient 40 and 46
what determines the amount of O2 bound to hemoglobin, and ultimately the amount of O2 in the bloodstream?
the partial pressure of O2 in arterial blood
-arterial blood O2 pressure drops, O2 delivery to tissues is compromised bc less O2 is bound to hemoglobin
at higher altitudes, pressure is low, so the overall diffusion gradient at skm is decreased from 60 mmHg to 15 mmHg which compromised athletic ability. What would be the body’s first way to buffer the reduced PaO2(the partial pressure of oxygen in the arterial blood) be?
struggling for O2, so increase pulmonary ventilation
-immediate increase in pulmonary ventilation, breathing deeper, tidal volume INC, resp rate INC
-try to buffer arterial drop in pp of O2
Calculate blood oxygen content if given PO2
What’s the importance of loading and unloading phases of the oxyhemoglobin dissociation curve and how the curve “shifts” during exercise?
100-80 % oxyhemoglobin saturation | oxygen content 20-15 ml O2/100 ml blood: O2 delivered to tissues
-
Loading Portion of Curve
-saturation stays high even with large changes in PO2
100->40 % oxyhemoglobin saturation | oxygen content 20->7 ml O2/100 ml blood -
UnLoading Portion of Curve
-saturation changes quickly with even small changes in PO2, allowing oxygen unloading to tissues
40->0 % oxyhemoglobin saturation | oxygen content 7->0 ml O2/100 ml blood
describe the a-VO2 difference at rest and during exercise.
-whats the difference
Muscle at rest
artery: 20 mlO2/100 ml blood
capillary: 4-5 ml O2/100 ml blood TAKEN UP so subtract
Vein: 15-16 ml O2/100 ml blood
20-15-16=4-5ml O2/100 ml blood taken up at capillaries
Muscle during intense aerobic exercise
artery: 20 mlO2/100 ml blood
capillary: 15 ml O2/100 ml blood TAKEN UP so subtract
Vein: 5ml ml O2/100 ml blood
20-5=15ml O2/100 ml blood taken up at capillaries
Difference:
more O2 is uptaken by capillaries during intenxe exercise which leaves a much more deox blood afterward
describe the transport of O2 in the blood and in the muscle
Myoglobin: takes O2 into muscle
- ONLY found in muscle, not in bloodstream
-binds O2 tighter than O2(left shift in curve, increases affinity)
-shuttles O2 to mitos
oxHgb comes by in the capillary and offloads the O2(PaO2=100), turns into Hgb leaves. the O2 binds to Mb in muscle (PO2=40)turning into oxmgb, o is delivered to mitos (PO2 is less than 5). big conc gradient between capillary and mito which allows for offloading
-during exercise PaO2 stays same at 100 but PvO2 and Po2 get as low as 15, and Po2 of mito can be as low as 1
Pa O2
arterial oxygen pressure
PA O2
Alveolar oxygen pressure
Sa O2
arterial O2 saturation
Ca O2
arterial O2 content
PAO2 –> Oa O2 –> SaO2 –> CaO2
pressure determines saturation which determines content
what determines how much oxygen binds to hemoglobin
high pressure= O2 binds well and tightly to hemoglobin molecules so it can be effectively delivered
oxyhemoglobin
oxygenated heomglobin
what determines blood oxygen content?
-what are the normative
[Hgb] = g/10 ml of g%
Normal =15 g% (range: 13-18 g%), women are lower. lower hemoglobin =hard to deliver O2
1g Hgb binds 1.34 ml O2 when 100% saturated
Blood O2 content=[Hgb] x 1.34 x % sat
eg. arterial blood:
CaO2=15g/100ml x 1.34 ml O2/g x 0.98 (can get thru finger tool to know O2 %)
= 19.7 ml O2/100 ml blood =197 ml/L
+ SMALL amount of O2 dissolved in plasma (3ml/L)
what determines blood oxygen content
how much O2 binds to 1 hgb when its fully saturated?
1.34 ml
what type of blood? arterial or venous?
higher PO2=more O2 bound to Hgb
po2=100 mm Hg
Hemoglobin =98.5% saturated
Arterial blood
what type of blood? arterial or venous?
lower PO2=less O2 bound to Hgb
Po2 =40 mm Hg
hgb=75% saturates
venous blood
GOOD FOR UNLOADING?
“shifting” of oxyhgb dissociation curve:
- leftward shift towards lower PO2 means increased affinity for O2 (more tightly bound
-rightward shifttowards higher PO2 means DEcreased affinity for O2(less tightly bound)
WHICH WOULD WE WANT DURING EXERCISE?
righward shift(decreased affinity)
-protected by buffer(straight line at top of graph)
-we want O2 to be easily stripped off (Offloaded) at muscle cells so it can be used
how to temp and Ph effect the shift of the oxyhgb dissociation cure to the right? (which is what we want during exercise)
Temp
-warmer temp decreases affinity(inc pressure) (43 degrees)
-20 deg increases affinity, 37 deg is body temp
pH
lower pH decreases affinity (more acidic)(inc pressure)(7.2)
-7.6 inc affinity, 7 .4 is body pH
decreased affinity allows for more O2 to be offloaded at the tissues bc its not as tightly bound to hemoglobin
-right shift promotes oxygen offloading, BUT it doesnt influence the top so we can still get oxygen binding tighly in the arterials, and it comes off easier as the curve dips
calculate CaO2 (content) in arterial blood given:
PaO2=15g/100 ml
Each gram of hemoglobin is capable of carrying 1.34 mL of oxygen
oxygen sat # = 98
CaO2= PaO2 x 1.34 x o sat
=15g/100 ml x 1.34 ml/g x 0.98
=20 ml O2/100 ml
=200 ml/L
calculate CvO2 (content) in venous blood(@ rest) given:
PvO2= see 40 mmHg so (O2 sat=75%)
PaO2=15g/100 ml
Each gram of hemoglobin is capable of carrying 1.34 mL of oxygen
oxygen sat # = 98
CvO2= PaO2 x 1.34 x o sat
= 15 x 1.34 x 75
=15 ml O2/100 ml blood
= 150 ml/L
RESTING a-v O2 diff= 50 ml O2/L of blood
calculate CvO2 (content) in venous blood(@ EXERCISE) given:
PvO2= see 15 mmHg so (O2 sat=25%)
PaO2=15g/100 ml
Each gram of hemoglobin is capable of carrying 1.34 mL of oxygen
oxygen sat # = 98
CVO2= PaO2 x 1.34 x osat
=15 g/100 ml x 1.34 x 0.25
= 50 ml O2/100 ml =50 ml/L
** EXERCISE a-v O2 diff= 150 ml O2/L blood**
summary
pressure –> saturation –> content
CaO2 doesnt change, CVO2 dec during exercise
- S shape ox oxhgb curve so buffer
-mgb transfers O2 in muscle
describe how CO2 is transported from the muscle to the lungs
what signals control ventilation during exercise
what is the ventilatory threshold?
what are the major and minor roles of ways that bicarbonate ions (HCO3) in blood co2 transport
Minor
-freely dissolved in plasma
-carbaminohemoglobin
Major
CO2 + H2O <–> H2CO3(carbonic acid) <–> H + HCO3 *bicarbonate ion)
-key enzyme in rbcs: CARBONIC ANHYDRASE
- H is buffered by Hgb (blood ph drops a tiny bit but its ok)
what do RBCs do for co2 transport? what role does it play
describe how CO2 is transported from the muscle to the lungs
Co2 from tissues (now in plasma) enters RBC and combines w water to make carbonic acid : CO2 + H2O <–> H2CO3 through enzyme carbonic anhydrase which immediately dissociates into a H ion and HCO3 (bicarbonate), H is buffered by Hgb so i doesnt cause a major change in blood pH.
HCO3 leaves RBC and circulates within plasma ultimately going towards lungs to exhale co2
in the tissues rxn goes forward: inc co2 formed = inc HCO3
in lungs rnx is in reverse: dec in HCO3 as CO2 is released
how does the respiratory center in the brain control the ventilation rate?
-inspiratory and expiratory
- in brainstem(medulla oblangata, pons)
-signals go to these centers to tell us to breathe heavier and more etc
-establish rate and depth of breathing via signals to respiratory muscles (involuntary)
-cortex overrides signals if necessary (voluntary)
what are the inputs that go to the respiratory centers?
1. central command from the brain
2. signals from active muscle (cause an input to inc inspiration)
3. central chemoreceptors
- stimulated by inc CO2 (H) in CSF
-inc rate and depth of breathing and removes excess CO2 from body
4. Peripheral Chemoreceptors(aortic and carotid bodies
- sensitive to arterial blood PO2, PCO2, H ion
5. Mechanoreceptors/stretch receptors(lungs)
-in pleurae, bronchioles, alveoli
-“sense” movement
6. Voluntary control(motor cortex)
-can adjust your breathing rate by choice
1 and 2 are neural factors
3 and 4 are chemical factors (respond to changes in bloodstream)
neurohumoral control of ventilation during exercise
humoral=chemical
-matches o2 delivery w demand
-levels off
how is ventilation during exercise linked to energy metabolism
VE matches VO2 during most low-moderate exercise intensities
-in vo2 max test, ventilation goes up in proportion to VO2 to a certain point (VENTILATORY THRESHOLD)
- above 60% VO2 max, VE increases DISproportionately (ventilatory threshold (VT))
-due to a disproportionate increase in PCO2 at higher exercise intensities
-above VT the increase in VE to remove CO2 is disproportionate to the bodies actual need for O2
-ventilation inc to maintain PaCO2 and PaO2
-primary stimulus at onset of exercise in inc in neural drive
-chemical changes fine tunes response
