Crr Week 2: Respiratory Physiology Ii

Front 1

What is the MAJOR factor regulating pulmonary blood flow?

Back 1

Partial pressure of O2 in alveolar gas (PAO2)

Front 2

Decreases in PAO2 below ______ mm H produce pulmonary vasoconstriction.

Is the mechanism of this related to depolarization or hyperpolarization of smooth muscles?

Back 2

70 mm Hg

Mechanism is related to depolarization of smooth muscles caused by hypoxia.

Front 3

Describe the direction of pulmonary blood flow in poorly ventilated and well-ventilated regions of the lung.

Back 3

Pulmonary blood flows away from poorly-ventilated regions and towards well-ventilated regions of the lung

Front 4

How does hypoxic vasoconstriction of the lung lead to right ventricle hypertrophy?

Back 4

Hypoxic vasoconstriction in the lungs can lead to pulmonary vascular resistance, causing right ventricle hypertrophy (to pump against an increased load)

Front 5

Describe the difference in vascular response to hypoxia in the lung versus hypoxia in other regions of the body?

Back 5

Hypoxia in the lung leads to vasoconstriction

Hypoxia in most other regions leads to vasodilation

Front 6

What are the effects of Thromboxane A2 and Prostacyclin?

Back 6

Thromboxane A2 --> vasoconstriction

Prostacyclin --> vasodilation

Front 7

The pressure gradient between which structures provide the driving force in zone 1 of the lung?

Back 7

Pressure difference between the artery and the alveoli

Front 8

The pressure gradient between which structures provide the driving force in zone 2 of the lung?

Back 8

Pressure difference between the artery and the avleoli

Front 9

The pressure gradient between which structures provide the driving force in zone 3 of the lung?

Back 9

Pressure difference between the artery and the vein

Front 10

What happens if PA were to be greater than Pa in zone 1 of the lung?

Back 10

The blood vessels would be compressed by the high Pa, so zone 1 will be ventilated but not perfused (becomes part of the physiologic dead space).

Front 11

Which zone of the lung has the greatest number of open capillaries and the highest blood flow?

Back 11

Zone 3

Front 12

Which veins participate in shunting coronary blood flow into the left atrium?

Back 12

Thebesian veins

Front 13

What kind of shunt occurs when there is an interventricular defect? (left to right, or right to left?

Back 13

Right-to-left

Front 14

What happens to the PaO2 and PaCO2 in the case of an interventricular defect?

Back 14

Right --> left shunting. Less blood is oxygenated.

PaO2 decreases (hypoxia)

PaCO2 changes only minimally (due to increased ventilation rate

??
In hypoxia, pCO2 increases, but the body compensates by increasing the ventilation rate, and bringing the PCO2 back down. Therefore the PaCO2 overall is only minimal.

Front 15

List 2 causes for Left-to-Right shunts?

Back 15

1. Patent ductus arteriosus (PDA)
2. Traumatic injury

Front 16

What does the V/Q ratio represtent?

Back 16

Alveolar ventilation / pulmonary blood flow

Front 17

Which zone in the lung has the highest V/Q raio?

Back 17

Zone 1

(V/Q = alveolar ventilation/ pulmonary blood flow)

Front 18

What is the average V/Q value for the entire lung?

Back 18

0.8

(V/Q = alveolar ventilation / pulmonary blood flow)

Front 19

If V/Q is normal, then what will the values of PaO2 and PaCO2 be?

Back 19

PaO2 = 100 mm Hg

PaCO2 = 40 mm Hg

Front 20

Is the PaO2 higher in zone 1 or zone 3 of the lung?

Back 20

Zone 1

Front 21

Is PaCO2 higher in zone 1 or zone 3 of the lung?

Back 21

Zone 3

Front 22

If both blood flow and ventilation are "low" in the upper lung and "high" in the lower lung, why does the V/Q ratio change from zone to zone?

Back 22

Regional variations in ventilation are not as great as regional variations in blood flow.

So, the lower portions of the lung have greater increases in blood flow, decreasing the ratio of V/Q when traveling from Zone 1 to Zone 3.

Front 23

In which region of the lung will PaO2 be the lowest and PaCO2 be the highest?

Back 23

Zone 3

Front 24

Describe the V/Q ratio in a "dead space" region of the lung.

Back 24

V/Q = infinity

(No blood flow in dead space; Q = ZERO)

Front 25

Describe the V/Q ratio in a shunt.

Back 25

V/Q = ZERO

(V = zero)

Front 26

What are the relative values (high/low) of PO2 and PCO2 when V/Q > 0.8?

Back 26

high PO2 and low PCO2

(zone 1)

Front 27

List the 4 basic components of the respiratory system that control breathing.

Back 27

1. Chemoreceptors (for O2 or CO2)
2. Mechanoreceptors in the lungs and joints
3. Control centers for breathing in the brain stem
4. Respiratory muscles

Front 28

Where is the apneustic center located and what is its function?

Back 28

Lower pons

Functions to PROMOTE inspiration by stimulation of the inspiratory neurons in the medulla oblongata
(this delays the "switch off" from the pneumotaxic center)

Front 29

Where is the pneumotaxic center located and what is its function?

Back 29

Rostral dorsal lateral pons

It antagonizes the apneustic center, cyclically sending the "switch off" signals to INHIBIT inspiration.
This decreases the tidal volume and increases respiratory rate.

Front 30

Which portion of the brain is involved in voluntary control of breathing?

Back 30

Cerebral cortex

Front 31

What are the four main centers in the brain to regulate respiration?

Back 31

1. Inspiratory center
2. Expiratory center
3. Pneumotaxic center
4. Apneustic center

Front 32

Which two respiratory control centers are located in the pons?

Back 32

1. Pneumotaxic center
2. Apneustic center

Front 33

Which two respiratory control centers are located in the medulla?

The dorsal respiratory group of neurons comprises which center?

Back 33

1. Inspiratory center (<-- dorsal group)
2. Expiratory center

Front 34

What is the function of the inspiratory center?

Back 34

Controls the basic rhythm for breathing by setting the FREQUENCY of inspiration

Front 35

The inspiratory center receives input from which controls?

How does it send motor output to the diaphragm?

Back 35

1. Peripheral chemoreceptors (via CN IX and CN X)
2. Mechanoreceptos (CN X)

*Sends motor output via Phrenic N

Front 36

When does the expiratory center become active?

Back 36

Becomes active during exercise

Front 37

What is the term for an abnormal pattern of breathing with prolonged inspiratory gasps, followed by brief expiratory movement?

Back 37

Apneusis

Front 38

List 3 causes of apneusis.

Back 38

1. Damage to the pons or upper medulla caused by strokes or trauma
2. Concurrent removal of input from the vagus nerve and the pneumotaxic center
3. drugs such as ketamine

Front 39

The absence of the pneumotaxic center will result in what sort of abnormal breathing?

Back 39

Increase in depth of respiration and a decrease in respiratory rate.

(Normal breathing rhythm typically persists)

Front 40

What is the effect of hyperventilation on PaCO2 and pH?

Back 40

Decrease in PaCO2
Increase in pH

Front 41

Where are central chemoreceptors located?

Back 41

Ventral surface of the medulla
(near the point of exit of the CN IX and CN X)

Front 42

Do central chemoreceptors communicate directly or indirectly with the inspiratory center?

Back 42

Directly

Front 43

What is the direct stimulus for central chemoreceptors?

Back 43

pH of the CSF

(this is an indirect response to changes in arterial PCO2)

Front 44

Will decreases in pH of CSF result in hyper or hypoventilation?

Back 44

Hyperventilation

Front 45

Which form of CO2 is the blood brain barrier permeable to?

Back 45

Permeable to CO2
Relatively impermeable to HCO3-

Front 46

Where are peripheral chemoreceptors located?

Back 46

1. Aortic bodies (on the arch of aorta)
2. Carotid bodies (on common carotid)

Front 47

Peripheral chemoreceptors act principally to detect variation of...?

How is information relayed to the medullary inspiratory center?

Back 47

PO2 in the arterial blood
(also monitor arterial PCO2 and pH).

*Info relayed via CN IX and CN X

Front 48

How do peripheral chemoreceptors detect variation of the PO2 in a "very unique way"?

Back 48

Peripheral chemoreceptors do not respond until PO2 decreases to less than 60 mm Hg.

(So, if arterial PO2 is anywhere between 100 and 60 mm Hg, the chemoreceptors will not respond).

Front 49

Are central or peripheral chemoreceptors more important in the detection of PCO2?

Back 49

Central chemoreceptors

Front 50

Which peripheral chemoreceptors detect changes in H+?

Back 50

Only the chemoreceptors in the carotid bodies

(changes in H+ detected is independent of PCO2 changes)

Front 51

What is the result of peripheral chemoreceptors detecting decreased arterial PO2 levels?

Back 51

Breathing rate is increased

Front 52

What is the result of peripheral chemoreceptors detecting increases in arterial PCO2 or decreased arterial pH?

Back 52

Breathing rate is decreased

Front 53

Where are mechanoreceptors located that are involved in breathing control?

What is their function?

Back 53

Smooth muscles of the airways

Initiate the Hering-Breur reflex, which is a reflex leading to a prolonged expiratory time-- decreasing breathing rate

*Inhibits Inspiratory center

(negative feedback reflex)

Front 54

What reflex is initiated by stretch receptors of smooth muscles (mechanoreceptors)?

Back 54

Hering-Breuer reflex

Front 55

What is the action of joint and muscle receptors?

Back 55

Instruct the inspiratory center to increase the breathing rate

Front 56

Which muscle receptors are important in the early/anticipatory ventilation response to exercise?

Back 56

Joint and muscle receptors

Front 57

Where are irritant receptors located?

What are they sensitive to?

Back 57

Between epithelial cells lining the airways

Noxious chemicals and particles

Front 58

What sort of reflex results from irritant receptors?

Back 58

Reflex constriction of bronchial smooth muscle and an INCREASE in breathing rate

Front 59

Where are juxtacapillary (J) receptors located?

Which nerve are they innervated by?

Back 59

In the alveolar walls (interstitium) and near the capillaries?

Innervated by the Vagus N.

Front 60

How are juxtacapillary receptors actived? (2)

What is the result of their activation?

Back 60

1. Engorgement (saturated with fluids) of pulmonary capillaries with blood
2. Increases in interstitial fluid volume

*Increase in breathing rate.

Front 61

How can you explain left-sided heart failure causing rapid, shallow breathing?

Back 61

Left-sided heart failure will result in engorgement of pulmonary capillaries with blood.
This activates juxtacapillary (J) receptors, which cause rapid, shallow breathing

Front 62

Why are the mean values of PO2 and PCO2 in arterial blood unchanged during exercise?

Back 62

Quick adjustments in ventilation via peripheral and central chemorecptors compensate.

(breathing rate is increased)

Front 63

What is the effect of exercise on arterial pH?

Back 63

pH may decrease due to the buildup of lactic acid

Front 64

How does the PCO2 of mixed venous blood change during exercise?

Back 64

PCO2 increases because skeletal muscle is adding more CO2.

Front 65

How can alkalosis be treated?

Back 65

Carbonic anhydrase inhibitors (acetazolamide)

Front 66

How might cardiac muscle adapt to high altitude?

Back 66

Hypertrophy of the right ventricle

Low PO2 produces hypoxic ventilation, leading to increased pulmonary arterial pressure, and potentially R ventricle hypertrophy

Front 67

How can high altitude cause hyperventilation?

How can it lead to alkalosis?

Back 67

Low PO2 may be severe enough (< 60 mmHg) to activate peripheral chemoreceptors to produce hyperventilation

This can also lead to alkalosis (hyperventilation decreases PCO2, resulting in increased pH).

Front 68

What causes acute altitude sickness?

Back 68

Initial hypoxia and respiratory alkalosis

Front 69

What is the difference between hypoxemia and hypoxia?

Back 69

Hypoxemia is a decrease in arterial PO2
Hypoxia is a decrease in O2 deliver, or utilization by, the TISSUES.

Front 70

List 3 pathological causes of an increased A-a gradient.

Is supplemental O2 helpful for these conditions?

Back 70

1. Diffusion defect (fibrosis)
2. V/Q defect
3. Right-to-Left shunt

Supplemental O2 is helpful for the first two, but it is not helpful for R-to-L shunts

Front 71

List 5 causes of hypoxia.

Back 71

1. Decreased cardiac output
2. Hypoxemia (reduced % Hb-saturation)
3. Anemia (reduced Hb concentration)
4. Carbon monoxide poisoning
5. Cyanide poisoning
4.