Exam 4: Respiratory L4

Question 1

Oxygen Transport in the Blood:
Oxygen is carried in the blood in two forms:

1.

2.

Answer 1

Oxygen is carried in the blood in two forms

1. Dissolved
2. Bound to Hemoglobin

Question 2

Dissolved Oxygen:

• Measured clinically as ______
• Amount that can be dissolved follows ____ Law
• Per 1 mmHg of PO2 —–> ______ mL 02/100 mL blood
• normal blood —–> ____ mL O2/ 100 mL blood

Answer 2

Dissolved Oxygen:
- measured clinically as PaO2 (blood gas analysis)

• amount that can be dissolved follows henry’s law (concentration of solute in gas is directly proportional to partial pressure)
• Per 1 mmHg of PO2 —> 0.003 mL O2 per 100 mL blood
• normal blood has 0.3 mL O2/ 100 mL

Question 3

How much oxygen do we use per minute in the blood?

How much of that does dissolved O2 provide?

Answer 3

Normal O2 consumption is roughly 250 mL O2/min

Dissolved gives us 15 mL of O2 per minute

(dissolved O2 is not enough)

Question 4

Dissolved Oxygen:

• ______ percentage of total O2
• Under normal conditions it is _____

Calculation sample question: What is the PAO2 if you breathe 100% oxygen and the PAco2 is 45 mmHg (R = 0.8)

Answer 4

Dissolved Oxygen:

• SMALL percentage of total O2 in blood
• Under normal conditions its almost negligible

Final answer: 657 mmHg

Question 5

Hemoglobin:

How many heme groups are there?

How many polypeptide chains? Which kind?

What is adult hemoglobin vs fetal hemoglobin

The binding/dissociation of O2 occurs in ____ and changes ______

Answer 5

Hemoglobin:

4 heme groups containing iron (this is where oxygen binds)

There are four polypeptide chains (2 alpha and two beta), this is for HbA

For kids less than a year old, HbF has 2 alpha globin and 2 gamma globin chains

The binding/dissociation of O2 occurs in milliseconds and changes light absorption of Hb (red means oxygenated, blue means deoxy)

Question 6

Explain the two states of Hb related to O2 binding

Explain O2 binding on heme

Answer 6

Hb has two states, tense and relaxed

Tense State (T) : no oxygen bound, low affinity for O2

Relaxed State (R): oxygen bound, high affinity

Oxygen binding is reversible, and also the oxygen binding on Hb is cooperative (sigmoidal curve)

That means the likelihood of oxygen binding goes up with each oxygen bound

Question 7

How much Hb is bound to oxygen within the normal range of P_O2 ? Draw the oxygen dissociation curve to help.

What is the normal unloading of oxygen by hemoglobin (in mL O2 per 100 mL blood)

Answer 7

Most Hb is oxygen bound within the range of normal P_O2 .

Curve is shown in attached picture.

Normal unloading is approx 4.5 mL O2 per 100mL

Question 8

Oxyhemoglobin Dissociation Curve:
At P_O2 > 60 mmHg what are the changes in Hb saturation

(what does that mean at those pressures)

At P_O2 < 60 mmHg : small changes in pressures lead to _____

(what does that mean?)

Answer 8

At P_O2 > 60 mmHg , small canges in Hb saturation (loading and transport at these pressures… facilitates normal oxygen transport to organs/cells)

At P_O2 < 60 mmHg: small changes in pressure lead to release of large amounts of O2

(facilitates release of oxygen to organs and cells)

Question 9

The oxyhemoglobin saturation curve is NOT static.

The curve responds to the local enviornment to ______

Explain what a right ward vs leftward shift means

Also explain P50 and how that is effected by left or rightward shift

Answer 9

The oxyhemoglobin saturation curve is NOT static. The curve responds to the local enviornment to modulate loading and unloading.

P50 is the pressure at which 50% of the Hb are oxygen saturated

A left shift of the curve means an INCREASE in Hb-O2 binding (decrease in P50, meaning an increase in Hb O2 affinity)

A rightward shift of the curve means a DECREASE in Hb-O2 binding. (increase in P50, meaning Hb has a decrease in O2 affinity)

Question 10

Explain which physiological factors cause a leftward shift of the Hb-O2 saturation curve

Explain which factors cause a rightward shift in the curve

Answer 10

Leftward Shift in the Curve (meaning increase in Hb-O2 affinity) : Decrease in temp, Decrease P_CO2 , Decrease in 2,3-DPG, and a decrease in H+ ions (meaning increased pH)

Rightward Shift in the Curve (meaning decreased O2 affinity): Increased temp, Increased P_CO2 , Increase in 2,3-DPG, Decrease in pH ( increase in H+ ions)

Question 11

Explain the Bohr Effects on the Hb-O2 saturation curve

Answer 11

Bohr studied the effects of pH and PCo2 on the Hb-O2 saturation curve

An increase in pH (decrease in H+ ions) and a decrease in P_CO2 causes a leftward shift of the curve (increased oxygen affinity)

A decrease in pH (increase in H+ ions), and an increase in P_CO2 cause a rightward shift in the curve (decreased oxygen affinity)

Question 12

Cheat code for hemoglobin oxygen saturation curve:

As X factor increases, Hb binding of oxygen ____

Just be aware of pH relationship to H+ ions

Answer 12

Cheat code:

As X factor increases, the Hb binding of oxygen decreases (shifts curve to the right)

(factors include temp, PCO2, 2,3-DPG, and H+ ions)

Just remember that decrease in pH means increase in H+ and vice versa

Question 13

Metabolically active tissues will have an _____ in all of the factors, causing the dissociation curve to shift to the _____

Answer 13

Metabotically active tissues will have an increase in all of the factors, causing the dissociation curve to shift to the right and causing a decrease in the O2 affinity

Question 14

Explain what happens to the hemoglobin oxygen saturation curve when the temperature drops vs rises

Answer 14

When the temperature drops, the curve shifts to the left, and oxygen affinity for Hb increases. Thus, not only does the blood get redistributed in cold weather, but also the blood that does get to the extremities does NOT unload its oxygen

When temperature rises, the sat curve gets shifted to the right, meaning more O2 is being unloaded in the tissues because the Hb o2 affinity decreased

Question 15

What two factors constitute the Bohr Effect?

Answer 15

Bohr Effect: pH and CO2

Question 16

The Bohr Effect: pH and CO2

What is hypercapnia?

How does CO2 react with Hb and affect O2 binding?

How does it compare to the effects of pH?

Answer 16

Hypercapnia = high CO2

CO2 does not directly compete for binding sites with O2. Instead, CO2 binds to amino groups and creates a carbamino Hb which decreases O2 binding

Therefore, high CO2 will shift the curve to the right, decreasing O2 affinity

The effects of CO2 are minor compared to pH

Question 17

The Bohr Effect:

High CO2 leads to ____ pH

Respiratory acidosis ______ O2 affinity

Combo of both pH and CO2 constitutes the Bohr Effect: explain what needs to happen for a left or rightward shift

Answer 17

High CO2 leads to lower pH

Respiratory acidosis decreases O2 affinity

Bohr Effect:

low pH and high CO2 decreases Hb oxygen affinity and shifts the curve to the right

Higher pH and lower CO2 levels increase the HB O2 affinity and shifts curve to the left

Question 18

2,3 DPG

Preferentially binds to ____

_____ affinity of Hb for oxygen (allosterically)

Increased DPG in _____ conditions

Answer 18

2,3 DPG preferentially binds to deoxygenated Hb

Decreases affinity of Hb for oxygen (allosterically)

Increase of DPG shifts curve to the right

There is Increased DPG in low oxygen conditions (where you want more oxygen dropped off)

Question 19

Final RECAP on Hb-O2 saturation curves:

Explain what causes left ward vs rightward shift in the following conditions, and note how each shift affects affinity and P₅₀
Temp

P_CO2

2,3 DPG

pH

Answer 19

Leftward Shift: Increased Affinity (Decreased P₅₀ )

• Decreased temp, decreased PCO2, decreased 2,3-DPG, and increase in pH (essentially a decrease in H+ ions)

Rightward shift: Decreased O2 affinity (increased P₅₀)

• Increased temp, increased PCO2, increased 2,3-DPG, and decreased pH (increase in H+ ions)

Question 20

Carbon Monoxide:

Hb affinity for CO is ______ than the affinity of O2

At 1 mmHg CO _____ binding sites are occupied

In the presence of CO: Hb affinity for O2 is ____, causing ________

What does the CO Hb saturation curve look like?

Answer 20

CO and Hb:
Hb has a 200x greater affinity for CO than O2

At 1 mmHg CO, ALL binding sites are occupied

In the presence of CO: Hb affinity for oxygen is ENHANCED, which prevents oxygen unloaded on the tissues

“it’s a double whammy”.. not only is CO going to bind and occupy the binding sites, but the O2 that stays bound will not be unloaded in the tissues either

Question 21

Hb and CO:
CO binding “mimics” oxygen binding into the _____ state for _____oxygen affinity.

What does that mean for Hb O2 binding?

Answer 21

CO binding “mimics” oxygen binding into the relaxed state for enhanced oxygen affinity.

Hb not necessarily binding more O2 due to higher affinity, it’s just that the oxygen that is bound is less likely to unload/dissociate?

Question 22

Sickle Cell:

Which form of Hb is it?

It is a ___ AA substitution in the ___ chain

It is normal with oxygen: it ____ at low oxygen

The sickle cell shape causes ___ and ___

Answer 22

Sickle Cell:

HbS

Single AA subsitution in the BETA chain

It is normal with oxygen; crystallizes at low oxygen

Sickle cell shape, hemolysis, anemia

Question 23

Explain Hb within diabetes

Answer 23

Diabetes: Hemoglobin A1c

Increased blood glycose leads to increased cell glucose 6-P which increases the amount of glycosylated Hb

This glycosylation is irreversible. RBCs last for three months (120 days) so HbA1c gives an accurate 3 month running average of your blood glucose level

Question 24

For PaO2, which level of partial pressure of oxygen in the arteries is hypoxia, and which level is in danger?

Give both the mmHg level and the o2 saturation percentage

Answer 24

PaO2 > 80 mmHg means HYPOXEMIA (97.5%)

PaO2 = 60 mmHg means DANGER (90%)

Altering Hb saturation is just as dangerous as altering your oxygen intake

Question 25

How do you calculate the oxygen content in arterial blood…“CaO2”?

Answer 25

To calculate CaO2, you simply multiply O2 capacity by SO2.

1 g of Hb can bind to 1.34 mL of O2

That means at 100%, we have 20.1 mL O2/100 mLs

In order to calculate the oxygen content in arterial blood, you take the SpO2/SO2% as a decimal and multiply it by 20.1 mL O2/ 100mL

Question 26

CO₂ is carried in the blood in three forms:

1.

2.

3.

Which one is the VAST majority of how CO2 is carried in blood?

Answer 26

CO2 is carried in the blood in three different forms:

1. Dissolved
2. Bicarb
3. Carbamino compounts

BICARB is mainly how CO2 is transported in blood, at 69%

Question 27

Carbamino compounds as Co2 in blood:

How much in plasma

How much in RBCs

Answer 27

Carbamino compounds as CO2 transport within blood:

11% in plasma

89% in RBCs

Question 28

Dissolved CO2:

Measured clinically as ______

Within the blood, how many mLs of CO2 per 100mLs of blood?

How does that compare to oxygen?

Answer 28

Dissolved CO2 is measured clinically as PaCo2

remember little a is for arteries, big A is for alveoli

Within blood: 0.067 mLs CO₂/ 100 mLs of blood

Remember O2 was 0.003 mLs/100mL of blood

There is 20x more disssolved CO2 than O2 in blood

Question 29

The Bicarb Equation:
CO2 + H2O <-> H2CO3 <–> H+ + HCO3-

In plasma:

the conversion of CO2 to carbonic acid is ___

But what happens in RBCs?

Answer 29

In plasma: the conversion of CO2 to carbonic acid is SLOW, so in plasma the majority of CO2 will exist as CO2

BUT, RBCs have an enzyme called Carbonic Anhydrase which rapidly converts the CO2 to carbonic acid, which rapidly diffuses to bicarb

Question 30

Haldane Effect:

Increasing PO2 ______ Hb affinity for CO2, meaning CO2 is ________ where O2 is high.

Decreasing PO2 ______ Hb affinity for CO2, meaning CO2 is _____ where O2 is low.

At any PCO2, total CO2 content rises as ______.

Answer 30

Haldane Effect:

Increasing PO2 decreases Hb affinity for CO2. CO2 is released in the lungs where O2 is high.

Decreasing PO2 increases Hb affinity for CO2, meaning that CO2 is picked up in the systemic tissue where O2 is low.

At any PCO2, total CO2 content rises as PO2 falls.

Question 31

Haldane vs Borh

Haldane: Effects of ___ on Hb to increase/decrease ___ binding.

Bohr: Effect of ___ on Hb to increase/decrease ___ binding.

Answer 31

Haldane: Effects of O2 on Hb to increase/decrease CO2 binding. (unloading of CO2 in the lungs)

Bohr: Effects of CO2 on Hb to increase/decrease O2 binding. (unloading of O2 in the tissue)

Question 32

O2 transport is mostly bound to _____

Answer 32

O2 transport is mostly bound to hemoglobin

Question 33

Oxyhemoglobin binding is ____ and ____

(Hb is mostly oxygen bound; binding falls off significantly below ___ mmHg, facilitating ____)

Answer 33

Oxyhemoglobin binding is cooperative and reversible

Hb is mostly bound to oxygen; binding falls off significantly below 60 mmHg, facilitating transport and release

Question 34

Which physiological factors shift the oxyhemoglobin dissociation curve?

Answer 34

Temp, 2,3- DPG and then pH and CO2 (bohr effect)

Question 35

CO binds ____ more tightly than O2 and inhibits _____

Answer 35

CO binds 200x more tightly than O2 and inhibits O2 unloading

Question 36

CO2 transport is mostly as _____, also ___ and ___

_______ (enzyme) facilitates CO2 to bicarb in RCCs

Answer 36

CO2 transport is mostly bicarb ; also dissolved CO2, and as carbamino compounds

Carbonic Anhydrase facilitates CO2 to bicarb in erythrocytes/RBCs

Question 37

Hb-CO2 binding ______ with increasing PO2 (Haldane Effect)

Answer 37

Hb-CO2 binding decreases with increases PO2

This is called the Haldane effect

Question 38

Control of Respiration:

Two main tasks:

1.

2.

Answer 38

In order for the brain to control respiration, it has two primary tasks:

1. Establish automatic rhythmic breathing
2. Accomodate Changing Demand

Question 39

Draw the flowchart of control of respiration:

Central controllers

Effectors

Sensors

Answer 39

Question 40

What are the major sites of respiratory control:

1. For Automatic Respiration
2. For Voluntary Respiration

Answer 40

Automatic Respiration:

• Respiratory Control Center (medulla)
• Central Chemoreceptors
• Peripheral Chemoreceptors
• Pulmonary mechanoreceptors/sensory nerves

Voluntary Respiration:
Motor cortex ——> Corticospinal tracts

Question 41

What are the two areas within the medulla that help generate a breathing pattern?

Answer 41

Dorsal Respiratory Group (DRG): primarily inspiratory

Ventral Respiratory Group (VRG): inspiratory and expiratory

the DRG and the VRG act together to generate a breathing pattern

Question 42

Eupnea vs dyspnea

Answer 42

Eupnea: normal rhythmic breathing via alternating inspiratory and expiratory neuron activity

Dyspnea: not normal breathing pattern

Question 43

Overall the ____ and the ___ (areas within the brain) control breathing pattern

Answer 43

Overall, the pons and the medulla control breathing patterns

Question 44

Central Chemoreceptors:

located on the ______

Sensitive to changes in _______ (which comes from where?)

Answer 44

Central Chemoreceptors:

• Located on the ventrolateral surface of the medulla oblongata
• Sensitive to changes in pH within CSF (the CO2 within blood passes over the blood brain barrier, gets converted to H+ within the CSF and that’s what is being detected by these central chemoreceptors)

Question 45

Central Chemoreceptors respond to changes in ____ but not changes in _____

Answer 45

Central Chemoreceptors respond to changes in PCO2 but NOT to changes in PO2

Question 46

Where are the peripheral chemoreceptors located?

What do they respond to?

_____ cells are like neuro-clusters of cells responsible for chemoreception

Answer 46

Peripheral Chemoreceptors: Carotid Sinus and Aortic Arch

Respond to: Decreases in PO2, Decreases in pH (carotid only), and increases in PCO2

Glomus cells are like neuroclusters of cells responsible for chemoreception

Question 47

What are the only chemoreceptors that respond to changes in PO2?

Answer 47

Peripheral chemoreceptors (aortic arch and carotid sinus) are the only ones that respond to changes in PO2

Question 48

At what level of PaO2 do the peripheral chemoreceptors start firing?

Answer 48

Remember, a PaO2 of 60 mmHg or less is DANGER zone

So peripheral chemoreceptors start firing robustly at a PaO2 of less than 70-80 mmHg

Question 49

What is one of the only negative feedback loops within respiratory control?

Answer 49

Hering-Breuer Reflex (stretch receptors in the lungs)

Question 50

Pulmonary stretch receptors:

Prevent the lungs from ____

Explain inflation reflex vs deflation reflex

The Hering-breuer reflexes are largely inactive in ___, unless _____

Answer 50

Pulmonary stretch receptors:
Prevent the lungs from over-inflation

Inflation of lungs inhibits inspiratory muscle activity (HB inflation reflex)

Deflation of lung initiates inspiratory activity (deflation reflex)

Hering Breuer reflexes are largely inactive in adults, unless tidal volumes are very high

Question 51

Irritant Receptors:

That are they stimulated by?

Answer 51

Irritant receptors

stimulated by noxious gas, cigarette smoke, dust, cold air

Impulses travel through vagus nerve

May play a role in asthma

Question 52

J (juxtacapillary) receptors and bronchial C fibers:
Respond to _______

In alveoli and conducting airways

Answer 52

J receptors and bronchial C fibers respond to chemicals in pulmonary (J receptors) and bronchial (C fiber) circulation

Question 53

Nose/upper airway receptors (irritant receptors)

respond to what?

What happens to airflow then?

Answer 53

Respond to diving, aspiration, sneeze reflex

Airflow: the radius decreases but the velocity increases more so more turbulent airflow happens

Question 54

Ventilatory Response to CO2:

At higher PCO2, there will be ______ ventilation

The effect of CO2 on ventilation is independent of O2 at normal O2 levels,

BUT when we drop to lower O2 levels what happens?

Answer 54

At higher PCO2 there will be higher ventilation

At lower PaO2:

• Ventilation at a given CO2 level is even higher
• Ventilatory Response to CO2 (slope) becomes steeper

AKA at lower O2 levels, ventilatory response to CO2 increases more dramatically

Question 55

Central chemoreceptors are located near the _______. They respond to changes in pH within the ____, caused by diffusion of ____ across the blood brain barrier into CSF.

Peripheral chemoreceptors respond to changes in ______, _____, and _____. The response to PO2 is _____ above 50-60 mmHg.

Answer 55

Central chemoreceptors are located near the ventral surface of the medulla.

They respond to changes in CSF, caused through diffusion of CO2 into CSF.

Peripheral chemoreceptors respond to changes in PO2, PCO2 and pH. Response to PO2 is amll above PO2 of 50-60 mmHg.

Question 56

The _____ of the blood is the most important factor controlling ventilation., most of control is through the _______ chemoreceptors.

Answer 56

The PCO2 of the blood is most important factor controlling ventilation, most of control is through the central chemoreceptors.

Question 57

_________ are clinically the most important breathing abnormalities

Answer 57

SLEEP APNEA syndromes are clinically most important breathing abnormalities

Question 58

Explain the difference between Obstructive Sleep Apnea vs Central Sleep Apnea

Answer 58

Obstructive Sleep Apnea: pleural pressure is normal, but there’s an obstruction causing airflow to not get through upper airway

central Sleep Apnea/Ondine’s curse: NEURAL defect, where the airflow stops because you loose the rhythmic breathing/the pleural pressure changes stop

Question 59

What are the three main responses the body does via the lung when its under extremely high altitude?

Answer 59

Lung Responses in High Altitude:
1. Hyperventilation

2. Polycythemia
3. Pulmonary Vasoconstriction

Question 60

At high altitude, the atmospheric pressure is lower, which means the PAO2 ends up being _____

Explain what the peripheral chemoreceotors do in response

Answer 60

LOWER

which is why you compensate

Peripheral chemoreceptors will be firing on all cylinders since the PaO2 is less than 70-80mmHg

Therefore, you will hyperventilate. BUT that hyperventilation will in turn reduce your CO2 and increase the pH

Question 61

Explain the effects of polychtemia

Answer 61

Polycthemia:
Increase in Hb and O2 carrying capacity

Stimulated by hypoxemia after 2-3 days in altitude

So even though people at high altitudes have low PO2 and low SpO2, they have more Hb than normal and therefore are able to unload just as much oxygen in the tissues

Question 62

Hypoxic Vasoconstriction in Altitude:

Instead of being local, it’s now global

What affects does this have in the heart?

Answer 62

Global hypoxia will decrease the radius of all pulmonary vessels, heart will have to work harder, right side will be hypertropied after a prolonged period of time, and then the pt will get hypertension

Question 63

Key Concepts: Altitude

• ____ is the most important problem
• ____ is the most immediate adaption

(hypoxia is induced by ______)

(CO2 is _____ over the coming days)

_______ develops slowly in high altitude, but increases the O2 concentration in blood

• Alveolar hypoxia at high altitude can result in pulmonary _____, right heart ____, and ___

Answer 63

Low PO2 is most important problem

Hyperventilation is most immediate adaptation

Hypoxia is induced by peripheral chemoceptors

CO2 is brought to normal over the coming days

Polycythemia develops slowly in high altitude

Alveolar hypoxia at high altitude can result in pulmonary vasoconstriction, right heart hypertrophy, and pulmonary edema