Respiratory System & Its Regulation- Part 2

What is the carrying capacity of oxygen in the blood?

20 mL O2/100mL blood (1L O2/ 5L of blood)

How much O2 in the blood is bound to hemoglobin?

98%

How much O2 in the blood is dissolved in plasma?

less than 2%

What is oxyhemoglobin?

oxygen bound to hemoglobin

What is deoxyhemoglobin?

hemoglobin without oxygen

What does hemoglobin saturation depend on?

-PO2

-affinity between O2 and hemoglobin (attraction)

What does the oxygen hemoglobin dissociation curve display?

the amount of hemoglobin saturated with oxygen at different PO2 values

What occurs at the loading portion of the oxygen hemoglobin dissociation curve?

saturation of oxygen stays high even with large changes in PO2 (small changes in hemoglobin saturation per mmHg changes in PO2)

What occurs at the unloading portion of the oxygen hemoglobin dissociation curve?

saturation changes quickly with even small changes in PO2 allowing oxygen unloading to tissues

When PO2 is high (such as in the lungs), what part of the oxygen hemoglobin dissociation curve is this at?

loading portion

When PO2 is low (such as in body tissues), what part of the oxygen hemoglobin dissociation curve is this at?

unloading portion

How does the oxygen hemoglobin dissociation curve represent/fit with the body's needs?

large changes quickly in hemoglobin saturation during the unloading portion allows O2 to be extracted for active tissues

How does exercise change the unloading portion of the oxygen hemoglobin dissociation curve?

increases the amount of unloading

How does blood pH impact hemoglobin saturation?

when blood becomes more acidic, the oxygen-hemoglobin saturation curve is shifted to the right (Bohr effect)

What occurs when the oxygen-hemoglobin saturation curve is shifted to the right?

hemoglobin has a decreased affinity for oxygen

What encourages O2 loading at the lungs?

relatively high pH at the lungs

What is the pH in exercising muscle?

more acidic (relative to lungs) due to by-products of exercise indicating more oxygen is being unloaded from hemoglobin

How does blood temperature affect the oxygen-hemoglobin saturation curve?

warmer the blood temperature shifts the curve to the right

At a given PO2, what will happen to oxyhemoglobin saturation with an increase in muscle/blood temperature?

less saturation because O2 is delivered to working muscles

What is the blood-oxygen carrying capacity?

maximum amount of O2 blood can carry

What is the blood oxygen-carrying capacity based on?

hemoglobin content (12-18g of Hb / 100 mL of blood)

What is the average hemoglobin content in men and women?

men = 14-18g Hb

women = 12-16g Hb

How saturated is hemoglobin at rest?

98-99% saturated

At rest, what is the transit time of hemoglobin?

0.75 seconds

What is transit time of hemoglobin?

the time it takes for RBCs which contain hemoglobin, to pass from alveolar air to pulmonary capillaries

What happens to the transit time of hemoglobin during exercise?

it decreases because of the increase in heart rate indicating that oxygen saturation during exercise also decreases

What does 1g of Hb bind to?

1.34 mL O2

What is the blood oxygen-carrying capacity?

16-24mL O2 / 100mL of blood

How does anemia affect hemoglobin content and oxygen capacity?

decreases hemoglobin content which in return decreases oxygen capacity

What can lead to a wrongful diagnosis of anemia?

expansion of plasma volume

When is CO2 released as a by-product?

of carb and fat metabolism

What are the 3 ways CO2 is transported in the blood?

-as bicarbonate ions (~60-70%)

-dissolved in plasma (~7-10%)

-bound to hemoglobin (~20-30%)

What is the molecule called when CO2 is bound to hemoglobin?

carbaminohemoglobin

What does CO2 + water form?

carbonic acid (H2CO3)

Where does the formation of carbonic acid occur and what catalyzes it?

occurs in RBCs and is catalyzed by carbonic anydrase

What does carbonic acid dissociate into?

bicarbonate

What does the H+ produced in the dissociation of carbonic acid to bicarbonate bind to and what is the purpose?

binds to hemoglobin (as a buffer) and triggers the Bohr effect

Where do bicarbonate ions diffuse from?

from RBCs into plasma

When does CO2 diffuse out into alveoli?

when PCO2 is low (ex. in lungs), CO2 comes out of solution and diffuses out into alveoli

Does CO2 compete with O2 binding on hemoglobin?

no they each have their own binding site:

O2 binds to heme portion of Hb

CO2 binds to protein globin portion of Hb

What affects CO2-Hb binding?

-hemoglobin state

-PCO2

Does deoxyhemoglobin or oxyhemoglobin bind to CO2 more easily?

deoxyhemoglobin

An increase in PCO2 results in what and where does this happen?

results in easier CO2-Hb binding and occurs in active tissues and muscle cells

A decrease in PCO2 results in what and where does this happen?

results in easier CO2-Hb dissociation and occurs in the lungs

What is the arterial-venous oxygen difference (a-v)O2?

difference between arterial and venous O2

What happens to O2 extraction from rest to exercise?

increases dramatically

How is venous O2 and a-v O2 difference change as O2 extraction increases?

venous O2 decreases and a-v O2 difference increases

What is the arterial O2 content?

20 mL O2/ 100 mL blood

Does arterial O2 content change during exercise?

no

Does venous O2 content change during exercise?

yes

How does the venous O2 content change at rest and during heavy exercise?

rest = 15-16mL O2/ 100 mL blood

heavy exercise = 4-5mL O2/ 100mL blood (O2 was extracted for tissues)

What transports O2 in muscle?

myoglobin

Does hemoglobin or myoglobin have a higher affinity for oxygen?

myoglobin

How is the O2-myoglobin dissociation curve shaped differently than the O2-hemoglobin curve?

-at PO2 0-20 mmHg slope is very steep (reflects stronger attraction between Mb and O2)

-loading portion by PO2 = 20 mmHg

-releasing portion at PO2 = 1-2 mmHg (really low pressures)

What factors influence oxygen uptake and delivery?

-O2 content of blood

-blood flow

-local conditions (pH, temp)

How does O2 content of blood influence O2 delivery and uptake?

creates arterial PO2 gradient for tissue exchange

What is O2 content of blood represented by?

PO2 and Hb percent saturation

How does blood flow influence O2 delivery and uptake?

-decrease in blood flow results in decrease in delivery of O2 to tissue

-exercise increases blood flow to muscle

What conditions of pH and temp promote unloading in the tissue?

decrease in pH and increase in temp

How is pulmonary ventilation regulated?

-homeostatic balance between blood PO2, PCO2, and pH

-requires coordination between respiratory and cardiovascular systems

Is regulation of pulmonary ventilation voluntary or involuntary?

involuntary (can override it, but it is typically involuntary)

Where are respiratory centers for central chemoreceptors located?

brain stem (medulla and pons)

What is the function of respiratory centers for central chemoreceptors?

-establish rate and depth of breathing via signals to respiratory muscles

-cortex overrides signals if necessary

What stimulates central chemoreceptors?

increase in PCO2 in cerebrospinal fluid

Can H+ ions cross the blood brain barrier?

no because they are charged

How do central chemoreceptors respond to an increase in CO2?

increase rate and depth of breathing and remove excess CO2

Where are peripheral chemoreceptors located?

in aortic bodies and carotid bodies (next to peripheral baroreceptors)

What are peripheral chemoreceptors sensitive to?

decrease in PO2 (mainly) but also increase PCO2 and H+

What are some circumstances where peripheral chemoreceptors would induce increased ventilation?

-altitude (barometric pressure decreases)

-COPD, emphysema (pulmonary disease or anything that leads to hypoxemia)

What are the peripheral mechanisms of regulation of ventilation?

-peripheral chemoreceptors

-mechanoreceptors (stretch)

Where are mechanoreceptors found?

-pleurae

-bronchioles

-alveoli

What happens when the mechanoreceptors experience excessive stretch?

reduce the depth of breathing (Hering-Breuer reflex)

What is the function of the Hering-Breuer reflex?

prevents over inflation of the lungs (damage to lungs)

What role does afferent feedback from exercising limbs play in ventilation?

contributes to the fast initiation of the drive to breath early in exercise (as soon as you start moving)

What is the afferent feedback from exercising limbs proportional to?

proportional to the frequency of limb movement

Does aerobic training have influence on the respiratory system?

has little influence on the respiratory system

Does land exercise or swimming exercise induce more adaptations to the lungs?

swimming

How does swimming provide respiratory adaptations?

-decreases breathing frequency

-increases tidal volume

-increases minuet ventilation

How does aging impair respiratory function?

-impaired recruitment and distension of pulmonary capilalries during exercise

-NOT limited during exercise in highly fit older adults

What type of exercise is beneficial for those with asthma?

habitual aerobic exercise

What type of exercise is beneficial for prevention of pneumonia?

-habitual aerobic exercise

-greater exercise energy expenditure associated with lower disease risk