Respiratory Physiology Flashcards

Question

What is the most important muscle for respiration?

Answer 1

The diaphragm

Answer 2

* Active during **inspiration**: dome-shaped structure separating lungs from abdominal contents * When the diaphragm **contracts** it moves down, allowing the abdominal content to be pushed down and the *rib cage to be pushed outward* * OVERALL EFFECT: * Increase in thoracic volume when it contracts

Answer 3

* inspiratory pump muscle * Contract and lift the rib cage, promotes a lateral increase in the thoracic volume * Contract and lift the rib cage to promote lateral increase in the thoracic volume * expansion of thorax * Motion similar to lifting a bucket handle = bucket handle motion

Answer 4

* Inspiratory Pump muscle * Contract and pull sternum forward - increases anterior posterior dimension of the rib cage * Pump handle motion

Answer 5

* Expiratory pump muscles * Contraction forces lung to return to resting position

Answer 6

* Expiratory pump muscles * Relaxed at rest and recruited during forced expiration * Push the rib cage down to reduce the amount of air or reduce the volume of the thoracic cage

Answer 7

* Scalenes, sternocleidomastoid, and pectoralis minor * Not commonly active during resting breathing; active during exercise and forced respiration

Answer 8

1. Diaphragm 2. External intercostals 3. Parasternal intercostals

Answer 9

1. Abdominals 2. Internal intercostals

Answer 10

1. Diaphragm contracts * pushing the abdominal content down and expanding the thorax as air comes in 2. External intercostals and parasternal intercostals contract (bucket handle and pump motion) increasing volume of the thorax

Answer 11

Stronger contaction of the diaphragm, and recruitment of the accessory muscles - further expanding the thoracic cavity

Answer 12

* No active contraction * Relaxation of the inspiratory muscles (diaphragm, external and parasternal intercostals) * Air moves out because of lung recoil

Answer 13

* Abdominal muscles contract intensely * pushes abdominal content upward forcing the diaphragm higher than its resting level * Internal intercostals contract and push the rib cage down

Answer 14

* reduction in upper airway latency during sleep = reduction in openness of airway * Depressed tone of upper respiratory muscles is depressed and they become a floppy muscle * Air cannot go in and out = daytime sleepiness, low o2 saturation in blood and cardiovascular risks

Answer 15

* result of a problem with the neural control of breathing * Lack of excitatory drive = needed to maintain tone of resp. muscles as well as anatomical defect

Answer 16

* respiratory zone and at the level of the alveoli * At conducting zone = muco-ciliary escalator

Answer 17

**Muco-ciliary escalator:** * Two types of cells lining the surface of the trachea: * Goblet Cells - produce mucus * Ciliated Cells - have cilia on apical surface

Answer 18

There are two cell types lining the trachea that make up the muco-ciliary escalator: 1. Goblet Cell - produce mucus 2. Ciliated Cell - have cilia on the apical surface; movement has preferential direction * produce periciliary fluid Both cell types function in a coordinated manner to entrap inhaled biological and inert particulates and remove them from the airways

Answer 19

* Periciliary fluid * Quite liquid (low density) * Sits on top of the ciliated cells = **sol layer** * Allows cilia to move freely because of low density

Answer 20

Thick, dense mucus = **Gel layer** * Sparse * trap particulates that enter the resp system during inhalation

Answer 21

SOL Layer = periciliary fluid from ciliated cells Gel Layer = mucus from goblet cell

Answer 22

Through cilia movements: * cilia move in the SOL layer and the tip of the cilia touches the mucus and pushes it continuously in one direction * Cilia movement is **downward** in the **nasopharynx** and **upward** at the level of the **trachea** to eliminate mucus through the esophagus

Answer 23

Macrophages in the alveoli -phagocytose particulates and digest them

Answer 24

* Macrophahes phagocytose the silica dust/asbestos but cannot digest them * the silica dust/asbestos break/kill the macrophages which then disintigrate * releases chemotactic factors * promotes recruitment of fibroblasts into the alveoli * increases the introduction of collagen = stiffens the lungs * Results in **pulmonary fibrosis**

Answer 25

A pulmonary function test that determines the amount and the rate of inspired and expired at each breath

Answer 26

The volume of air moved IN OR OUT of the respiratory tract during each ventilatory cycle

Answer 27

The additional volume air that can be forcibly exhaled following a normal expiration * Can be assessed simply by expiring maximally to the Maximum Voluntary Expiration

Answer 28

The additional volume of air that can be forcibly inhaled following a normal inspiration; it can be accessed simply by inspiring maximally to the *Maximum Possible Inspiration*

Answer 29

The volume of air remaining in the lungs after a maximal expiration; it cannot be expired no matter how vigorous or long the effort ## Footnote **RV cannot be measured with a spirometry test** **RV= FRC-ERV** **(FRC: functional residual capacity** **ERV: expiratory reserve volume**

Answer 30

RV = (FRC-ERV) FRC: functional residual capacity ERV: Expiratory reserve volume

Answer 31

Prevents collapse of the alveoli (Atelectasis)

Answer 32

Capacities are measurements of lung _volumes_ and correspond to the sum of: 2 or more lung volumes

Answer 33

Maximal volume of air that can be forcible exhaled after a Maximal inspiration **VC = TV + IRV + ERV** TV: tidal volume IRV: Inspiratory reserve volume ERV: expiratory reserve volume

Answer 34

* Inspiratory capacity is the maximal volume of air that can be forcibly inhaled * **IC = TV + IRV** TV= Tidal Volume IRV = Inspiratory Reserve Volume

Answer 35

* The volume of air remaining in the lungs at the end of a normal expiration * **FRC = RV + ERV** Functional residual capacity RV" Residiual Volume ERV: Expiratory reserve volume

Answer 36

* Volume of air in the lungs at the end of a Maximal Inspiration * **TLC = FRC + TV + IRV = VC +RV**

Answer 37

Residual volume and any capacity that relies on RV in it's formula. Therefore, we cannot measure: Residual Volume Functional Residual Capacity (FRC) Total lung capacity (TLC) TLC = FRC +TV + IRV FRC = RV + ERV

Answer 38

500mL (Tidal Volume = air moved in or out of the respiratory tract during each ventilatory period)

Answer 39

The amount of air that is exchanged within a rate time, or within a minute **Total/minute ventilation = (tidal volume)(resp. freq)** **= (0.5L)(15/min)** **=7.5 L/min \*** **\***Not all of this will be available for gas exchange (have to take into account the anatomical dead space)

Answer 40

**Alveolar Ventilation**: The amount of air moved into the alveoli per minute * Will be LESS than Minute Ventilation as it depends on the anatomical dead space * Calculated by subtracting the anatomical dead space volume from the tidal volume and multiplying by the respiratory frequency: * **V_A= (TV - V_ADS) (Resp. Freq)**

Answer 41

Tidal volume (air that enters the resp system) is **_500_**mL and conducting airways have a volume of about **_150_**mL (volume of air that is leftover from previous breath; no gas exchange) Which means, ~1/3 of a normal breath is not available for gas exchange

Answer 42

Divers inhale slowly and very deeply; this improves ventilation of the lung - majority of minute ventilation is dedicated to or available for gas exchange _Deep breathing is more effective at increasing alveolar ventilation than is fast, shallow breathing_

Answer 43

Spirometry is used to determine the _forced expiratory volume_ in _1_ second(s) and the forced _vital capacity_

Answer 44

1. Forced expiratory volume in 1 second (FEV-1) 2. Forced vital capacity (FVC)

Answer 45

Forced Expiratory Volume in 1 second: * forced expiratory volume is how much of the vital capacity volume that can be expelled in one second

Answer 46

Forced vital capacity is about _5 Litres_ in a healthy person

Answer 47

Obstructive disease or restrictive disease

Answer 48

Patients affected by obstructive lung disease have shortness of breath due to difficulty in *_exhaling_* _all the air from their lungs_ because of _damage to the lungs or narrowing of the airways inside the lungs - exhaled airs comes out more slowly_

Answer 49

* FEV-1 is significantly reduced * Process of expiration is also much slower (shown by a lower slope) * FVC can be normal or slightly reduced * Ratio between FEV-1/FVC is also reduced (\<0.7)

Answer 50

* Patients cannot fully fill their lungs with air - restricted from expanding * Most often results from a condition causing stiffness in the lungs * Can also be caused by stiffness of the chest wall, weak muscles or damaged nerves

Answer 51

* FVC is reduced * FVC is reduced in patients compared to normal because less air enters therefore the IRV is much smaller than in a normal patient even though he has the full ability to expel * FEV-1 is reduced in comparison to a normal calculation * Ratio between FEV-1/FVC will be similar to a normal healthy person BUT the volume measured with FEV-1 and FVC will be reduced

Answer 52

Recall: FRC = is the volume remaining in the lungs after a normal, passive exhalation Can be measured with Helium dilution method

Answer 53

* Mechanical properties that are present in the lungs when no air is flowing * Necessary to maintain lung and chest wall at a certain volume * Include: * intrapleural pressure (P_IP), * transpulmonary pressure (P_PT), * static compliance of the lung and * surface tension of the lung

Answer 54

* Mechanical properties when the lungs are changing volume and air is flowing in and out (*necessary to permit airflow*) * Alveolar pressure * Dynamic lung compliance * airway and tissue resistance

Answer 55

Ventilation

Answer 56

Change in pressure, or the generation of a pressure difference, between the atmosphere and the alveoli that will move air into and out of the lungs

Answer 57

In ventilation, air flows by _bulk flow_ from a region of higher pressure to a region of lower pressure

Answer 58

For a fixed amount of an ideal gas that is kept at constant temperature the **pressure and the volume are inversely proportion** * The product of pressure and volume will be a constant * With an increase in volume, there will be a corresponding decrease in presure **P1V1=P2V2**

Answer 59

During the expiratory phase of the lungs, a reduction in volume will generate an increase in _alveolar pressure_

Answer 60

**Flow =** ΔP/R ΔP = Change in pressure (difference in pressure between the alveolar pressure and atmospheric pressure) R = Resistance

Answer 61

Lungs have a tendency to collapse due to _elastic recoil_

Answer 62

* Intrapleural pressure - Pressure that is inside the pleura * acts like a vacuum * Alveolar pressure (P_ALV) * Transpulmonary pressure (P_TP) - derived from the difference of the alveolar pressure minus the intrapleural pressure

Answer 63

Because the intrapleural space acts as a relative vacuum, the intrapleural pressure is _älways negative_

Answer 64

* Intrapleural pressure fluctuates with breathing but it is always _subatmospheric_ due to: _opposing directions of the elastic recoil of lungs and thoracic cage_ * What would result if the PIP = PALV * The lungs would collapse

Answer 65

_Transpulmonary Pressure (P_TP)_ is the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall

Answer 66

P__alv_should always be \> than P_IP in order to maintain the lungs expanded in the thorax

Answer 67

P_TP is a static parameter which does **not** cause airflow, but determines lung volume (V_L)

Answer 68

P_ALV is a dynamic component that determines air flow

Answer 69

During an inspiratory effort: * CNS sends an _excitatory drive_ to the muscles of inspiration (_diaphragm_, _intercostals_ and _parasternals_) * Muscles contract and generate an _increase_ in thoracic volume * Intrapleural pressure _decreases (becomes more subatmospheric ie more negative)_ * Transpulmonary pressure _increases_ * Lung volume _increases_ * Alveoli pressure _decreases (below atmospheric)_ * generates movement of _gas_ from low _pressure_ to high _pressure_

Answer 70

Expiration: * Relaxation of the _inspiratory_ muscles → * chest wall _recoils_ (goes back to its resting state) → * _intrapleural pressure_ moves back to a pre-inspiratory value→ * as transpulmonary pressure is equal to the alveolar pressure minus the intrapleural pressure, the transpulmonary pressure will also will be _reduced_ as the intrapleural pressure returns to pre-inspiratory values → * as transpulmonary pressure is also linked to lung volume, _lungs recoi_l and a reduce _volume_, generating _compression_ of the gas molecules inside the alveoli → * increase in _alveolar pressure_ so it is greater than the atmospheric pressure → * air will move from a region of high _pressure_ to a region of low _pressure_, flowing out of the lungs to the environment

Answer 71

Lungs are embedded inside the pleural tissue called: _visceral pleura_ The inside of the chest wall is lined by another pleural tissue called the _parietal pleura_

Answer 72

* Intertia of the respiratory system * Friction forces 1. friction between the different alveolar sacs 2. friction between the lung and the chest wall 3. Resistance that the airflow incurs when it enters the airway * accounts for 80% of total airway resistance

Answer 73

Airflow resistance is most sensitive to changes in radius when flow is _NOT laminar (turbulent)_

Answer 74

Mixture of laminar (linear) and turbulent (not smooth) * It takes extra energy to produce vortices = increases resistance * Airflow is transitional throughout most of the bronchial tree, at the ramifications or branches of the bronchial tree

Answer 75

In larger airways, such as the trachea, the larynx and the pharynx * larger diameter = velocity of gas molecules is higher resulting in turbulent flow

Answer 76

Poiseuille's Law R=(8ηL)/(πr⁴) n=viscosity L = length \*Based on this formula, as the radius is reduced, the resistance will dramatically increase\*

Answer 77

* **In Series** * Resistance is simply the sum of the individual resistances * **In Parallel** * The resistance at each specific generation, when there is respiratory airflow, will be given by the inverse of each specific resistance; * as a consequence, the respiratory resistance at the level of the small airways at the level of the respiratory zone is minimal

Answer 78

Because their overall resistance can change significantly in pathological conditions * small airways can easily be occluded: * as they are surrounded by smooth muscle, contraction of smooth mm will increase resistance

Answer 79

1. Small airways are surrounded by smooth muscle, contraction of which will increase resistance 2. **Edema**: presence of fluid in the small airways can reduce the space available for airflow to move in or for the air to flow into alveolar sacs 3. **Mucus** accumulation can reduce the alveolar space at the level of the bronchioles

Answer 80

Because lung compliance can be measured both in the presence or absence of airflow

Answer 81

Measure of the elastic properties of the lungs and a measure of how easily the lungs can expand * given by the magnitude of the change in lung volume produced by a given change in transpulmonary pressure * Determined from a plot of transpulmonary pressure (x-axis) and lung volume (y-axis) *compliance is the slope*

Answer 82

* Represents the lung compliance (elastic properties of the lungs) when no air is flowing through * To measure: * Pt is asked to make a maximal inspiration and then release a small amount of air, at which time lung volume and transpulmonary pressure are measured * this continues in intervals (where pt exhales small amount of air and then stops) * the curves illustrate the ability of the lungs to expand and how much effort is put into inhaling or increasing lung volume at each respiratory breath

Answer 83

* Lung compliance is low * Overproduction of collagen makes the lungs stiff which means that the patient has to make a big effort to expand the chest wall in order to increase the transpulmonary pressure that is responsible for changing the lung volume * A large change in transpulmonary pressure will result in a small change in lung volume (slope is reduced)

Answer 84

* Lung compliance is high * Gradual reduction in lung elastic components * Small change in transpulmonary pressure will result in a large change in lung volume * Slope increases * "floppy lungs" - lost alveolar tissue resulting in less surface respiratory membranes available for gas exchange

Answer 85

* Measured during periods of gas flow (either during inspiration or expiration) * Takes into consideration not only the **elastic properties** of the lungs, or the **stiffness**, but also the **airway resistance** that the air encounters during breathing that could potentially reduce the expansion of the lungs

Answer 86

Dynamic: * measured when air is flowing * elastic properties AND airway resistance * Usually less than or equal to static compliance (b/c of airway resistance) Static: * elastic properties when no air is flowing

Answer 87

At FRC, the slope of the curve will be **reduced** in the case of Dynamic compliance and it will be **increased** in the case of Static compliance

Answer 88

Hysteresis

Answer 89

What events do the numbers on the graph represent? 1. _Stable V_L_ * Collapsed lung - medium and small airways will be collapsed = little gas exchange * at low lung volumes, it's difficult to _pop open an almost completely collapsed airway_ therefore rising _P_TP_ has little effect on _V_L_ 2. _Opening of airways_ * First increases in _V_L_ reflect the popping open of the _proximal airways_ followed by their expansion and recruitment of others as air flows into the _alveolar sacs_ which progressively increases the _P_TP_ 3. _Linear expansion of open airways_ * When all airways are open, making _P_IP_ more negative by chest wall expansion inflates the lungs and increases _V_L_ in a linear fashion * _alveoli_ will expand until basically the _elastic_ properties of the lungs do not allow further expansion 4. _Limit of airway inflation_ * Curve reaches a plateau as it reaches the _limit_ of _airway inflation_ * At high _V_L_ lung compliance _decreases_

Answer 90

Difference between the inflation and deflation compliance pathway (Where compliance is measured as the slope of transpulmonary pressure (x)/Lung volume graph (y)) C= ∆V_L / ∆P_TP

Answer 91

Because a greater pressure difference is required to open a previously closed (or narrowed) airway than to keep an airway from closing; * Related to the elastic properties of the lungs

Answer 92

* Elastic components of lungs and airway tissue * anatomic structures of the lungs and tissues * **elastin and collagen** * Surface Tension at the air-water interface within the alveoli

Answer 93

Elastin and collagen are localized in _alveolar walls_, around _blood vessels_ and _bronchi_ * Influence: * how elastic or stiff the lung is * *Dynamic*: * the amount of these proteins varies considerably with changes in life

Answer 94

* Geometric arrangement of the molecules * **Elastin**: * Gives lung *high extensible properties* b/c of it's SPRING SHAPE * Improve the ability of lungs to *stretch* * **Collagen** * gives stiffness (like a strong twine = high tensile strength/inextensible) * increase in collagen causes fibrosis = low compliance = require higher P_TP to inflate lung at low volumes

Answer 95

* Healthy lung tissue * well organized with very regularly shaped alveoli and a dense network of alveoli within the lung tissue * Emphysema * still see some alveoli that are similarly shaped to healthy lung * many large alveolar spaces = ↓surface area available for gas exchange * ↑Compliance = small ∆pressure → large ∆volume * Floppy lungs = less elastic recoil (high compliance)

Answer 96

Surface tension: property or phenomenon that occurs at the level of the interface between the surface and the air * Makes lungs collapse or gives the lungs elastic recoil * Surface tension decreases lung compliance

Answer 97

The molecules of the fluid that are in contact with the air/fluid interface * molecules in the bulk of the fluid will tend to interact with each other (esp if they are polar) * water molecule deeply embedded in the liquid will interact with molecules in all directions forming strong bonds * Water molecules at the surface are interacting with water molecules but will have little interaction with gas = creates a strong attractive force at the level of the air interface **Surface tension =** measure of the attracting forces acting to pull a liquid's surface molecules together at an air liquid interface

Answer 98

Surface tension is seen at all air-fluid boundaries and arises as a result of: Hydrogen bonding of water molecules

Answer 99

If you fill an isolated deflated lung with liquid (saline in this case) so that there is NO air in the lung, the pathway of lung compliance is much steeper because surface tension is not involved - therefore, the effect of surface tension is to "cause" the surface to maintain as small an area as possible - influences mvmt to the right of the lung compliance curve

Answer 100

* Type I alveolar cells line the surface of the alveolar walls * They are in contact with fluid that contains surfactant * the internal surface of the alveoli is lined with a thin layer of fluid and air continuously comes in and out of the alveoli

Answer 101

Water molecules cover the alveolar surface creating substantial surface tension = reduces the volume of the ideal sphere (or alveoli)

Answer 102

Describes the equilibrium that balances the pressure necessary to keep the alveoli open and the tendency for alveoli to collapse P = 2T/r T = Surface tension r = radius * the smaller a bubble's radius = the greater the pressure needed to keep it inflated

Answer 103

According to Laplaces eqn, a large alveoli requires less pressure to remain open than does a small alveoli =means that there is a region of higher pressure in small alveoli and a region of lower pressure in larger alveoli

Answer 104

Because of surfactant - reduces surface tension at alveoli - makes alveoli stable against collapse

Answer 105

type ii alveolar cells (ie type ii pneumocytes)

Answer 106

1. Reduce the surface tension at the level of the alveoli 2. Improve lung compliance = less work needed to breath 3. stabalize alveoli against collapse 4. allows alveolar communication between dif sized alveoli without collapsing

Answer 107

Surfactant is a mixture of _phospholipids_ * for interest: dipalmitoyl-phosphatidylcholine (DDPC), Phosphatidyl-choline, surfactant apoproteins and Ca2+ * Recall: phospholipids are AMPHIPATHIC * hydrophobic and hydrophilic properties * **interferes with water-water interactions \***

Answer 108

* Surfactant, which is always present on the surface of the air/water interface in alveoli, will be closer together or further apart depending on the phase of the respiratory cycle * T/r ratio is constant across dif sizes of alveoli * because alveoli have equal concentration of surfactant, it must be organized differently based on size * small alveoli = surfactant is closer together * larger alveoli = surfactant is farther apart * surface tension is increased in large alveoli and decreased in small alveoli

Answer 109

you will have lower surface tension as seen in smaller alveoli

Answer 110

Allows the alveolar tension to change with inflation and deflation - thickness of the surfactant layer varies inversely with the surface area

Answer 111

They do not have enough surfactant in their lungs = have to make a large inspiratory effor to increase lung volume **infant respiratory distress syndrom** *dr administers surfactant to the airways*

Answer 112

Surfactant improves _compliance_ and stabalizes _alveolar size_

Answer 113

That ventilation is not equal throughout the lung: * ventilation was higher in the lower zone of the lung (bottom) and lower in the upper zone * If patient was laying flat, the highest ventilation was towards his back * Shows that *regional ventilation changes have to do with gravity and posture*

Answer 114

* There is *negative pressure* in the *intrapleural space* (**subatmospheric**) which changes between the top and bottom of the lung * P_IP is much *more negative* at the top of the lung than the bottom * P_IP is generated by the balance between the elastic recoil of the lung and the elastic chest wall * The lungs have weight and are affected by gravity * weight increases pressure = P_IPless negative (increase) at the bottom and decrease (more negative) at the top

Answer 115

* more deflated = can expand more = receive larger portion of inspired air At the beginning of an inspiration, the alveoli that are at the bottom of the lungs start being *more deflated* because the transpulmonary pressure that generates the lung volume is influenced by the values of intrapleural pressure; when inflation occurs, small changes in P_IP will generate large changes in V_L

Answer 116

States that in a mixture of gas, such as air, each gas has its specific pressure and the total pressure of this mixtures is given by the **sum of the individual pressures**

Answer 117

Gas exchange occurs at the level of the _Respiratory membrane_ (very thin layer of tissue) * contains the fluid, epithelial cells in the alveoli, interstitial space, basement membrane of the capillary epithelium, and the epithelium * Thinness is an advantage

Answer 118

Explains diffusion through the respiratory membrane: * States that the rate of transfer of a gas (V; L/min) through a sheet of tissue per unit time is proportional to the Surface area of the membrane (A) and depends on the difference in partial pressures between the two environments, (P1-P2) and inversely proportional to the thickness (T) of the membrane. * D= diffusion constant **V_{gas =}** (A÷T) • D • (P1-P2)

Answer 119

The diffusion constant (in _FICK's_ law) is proportional to the _solubility of the gas_ and inversely proportional to _square root of the molecular weight_ Conclusion? * Solubility of the gas in the fluid will influence the diffusion process * CO2 is much more soluble than oxygen * CO2 will have a faster diffusion process compared to O2

Answer 120

CO2 diffuses faster because it has a much higher solubility than O2

Answer 121

The amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in with the liquid is in equilibrium

Answer 122

Partial pressure and solubility [gas] in liquid = (P • Sol) Therefore, if two gases are at the same PP but differ in sol, their content within sol'n will differ \*ONLY GAS DISSOLVED IN SOL'N CONTRIBUTES TO PP (O2 bound to Hb = no longer dissolved)

Answer 123

PP of water is variable and depends on _how saturated the air is_

Answer 124

At the level of the alveoli: * PPO2 is _reduced_ * PPCO2 is _increased_

Answer 125

Venous blood returns to the heart from the systemic circulation, and then travels by the pulmonary arteries to the lung capillaries. * Mixed venous blood containing _oxygen_ and _carbon dioxide_ returns to the lung capillaries available for the gas exchange * PO2 in the atmosphere is _160 mmHg_; PO2 at the level of the alveoli is _105_ mmHg * When the mixed venous blood enters the pulmonary circulation, PO2 is _40_ mmHg _(lower in blood than in atmosphere)_ * The diffusion process from the alveoli to the lung capillaries is very fast and _oxygen will move from the alveoli to the lung capillaries as soon as air enters the alveoli_ * Blood exiting the lung is equivalent to the gas that is present at the level of the _alveoli_ * PO2 in blood exiting the pulmonary capillaries is 100 mmHg (similar to 105 mmHg seen in the alveoli)

Answer 126

* Air enters the respiratory system and reaches the alveoli where it is warmed up and humidified; partial pressure of water will increase and the partial pressure of O2 will decrease * As soon as air enters the alveoli = lots of blood available for diffusion = reduce Po2 * Once air enters the alveolar network, it mixes with air that makes up the functional residual capacity = decrease PO2

Answer 127

1. PO2 in the atmosphere * higher altitudes = reduced atm pressure = decrease PO2 proportionally 2. Alveolar ventilation * how much air is exchanged per unit time * ↑ alveolar ventilation = more air will be continuously exchange * Air at level of alveoli will be more similar to the air at the level of the atmosphere 3. Metabolic rate (eg exercise) 4. Lung perfusion * change in cardiac output = change in amount of blood passing through resp. system

Answer 128

1. Atmospheric PCO2 (essentially zero) * CO2 moves out of blood into alveoli = increases alveolar PCO2 2. Alveolar ventilation * decrease in alveolar ventilation will lead to less exhalation of CO2 from alveoli to atm and therefore PCO2 will be increased in the alveoli 3. Metabolic rate = increases PCO2 4. Lung perfusion

Answer 129

Increasing **alveolar ventilation (VA)** will increase alveolar P**_O2_** and decrease alveolar PC**_O2_** * Due to increased ventilation, there will be an increase in PO2 because the alveolar air will be more similar to the air that is present in the atmosphere * When the ventilation is increased, more CO2 is eliminated

Answer 130

Reduce the amount of gas exchange between the alveoli and the atmosphere = increase in alveolar PCO2 and decrease in alveolar PO2

Answer 131

PP of gas in alveoli determines arterial levels

Answer 132

The respiratory membrane is extremely fragile High bp can damage the respiratory membrane and edema and influx of plasma or RBC could move into the lungs and affect resp function

Answer 133

Resistance defined by Poiseuille's law * length of vessels and the fourth power of the radius affects resistance * short wide vessels consistently reduce the resistance of the pulmonary circulation

Answer 134

* Thin walled vessels * Vessels have very little smooth mm and small changes in pressure = large expansion * vessels will dilate in response to modest increase in arterial pressure

Answer 135

The pulmonary system is _low_ pressure, _low_ resistance, and _high_ compliance

Answer 136

They are equal

Answer 137

If the capillary pressure falls below alveolar pressure, the capillaries close off, diverting blood to other pulmonary capillary beds with higher pressures

Answer 138

Ventilation/perfusion ration is the balance between the ventilation (bringing O2 into/removing CO2 from the alveoli *atm-alveoli*) and the perfusion (removing O2 from the alveoli and adding CO2 *alveoli-blood*)

Answer 139

Alveolar (and therefore arterial) levels of O2 and CO2

Answer 140

The greater the ventilation, the more closely alveolar PO2 and PCO2 approach their respective values in inspired air (ie closer to atm values)

Answer 141

The more closely the composition of local alveolar air approaches that of mixed venous blood (reduced PO2 and increased PCO2)

Answer 142

* Seen when there is a collapsing of the lung capillaries, *pleurisy* or other diseases that affect the vasculatory system * Blood flow is obstructed or occluded * No blood available for gas exchange * ↑PO2 at alveoli (no O2 passing from lungs to caps) * ↓PCO2 at alveoli (no CO2 entering lungs from blood) * Region is **under-perfused** or **under-ventilated** * Anatomical dead volume

Answer 143

* Obstruction: collapsed bronchi or bronchioles * no gas exchange between the alveolar air or alveolar space and the atmosphere * Blood still moves through alveolar space and contacts alveolar spce through the resp membrane * Decrease in **alveolar** **PO2** and increase in **PCO2** * Amount of blood passing through this system is called a **shunt**

Answer 144

refers to the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries * alveolar occlusion =\> V/Q (ventilation/perfusion) ratio is low

Answer 145

Both _blood flow (perfusion)_ and _ventilation_ decrease from the bottom of the lungs to the top of the lungs * The slope of the two lines representing perfusion and ventilation is different * This leads to the ventilation/perfusion ratio being _lower_ at the bottom of the lungs and _higher_ at the top of the lungs

Answer 146

Homeostatic mechanisms exist to limit _mismatch_ between ventilation and perfusion

Answer 147

* **Pulmonary hypoxic vasoconstriction** * a homeostatic mechanism that is intrinsic to the pulmonary vasculature. Intrapulmonary arteries **constrict** in response to alveolar hypoxia (↓O2), diverting blood to better-oxygenated lung segments, thereby **optimizing ventilation/perfusion matching** and systemic oxygen delivery

Answer 148

a homeostatic mechanism that is intrinsic to the pulmonary vasculature. Intrapulmonary arteries **constrict** in response to alveolar hypoxia (↓O2), diverting blood to better-oxygenated lung segments, thereby **optimizing** **ventilation/perfusion matching** and systemic oxygen delivery

Answer 149

1. Dissolved in plasma (~2% - O2 has low solubility) 2. Combined with hemoglobin (~98%)

Answer 150

Dissolved O2 follows _Henry's_ Law * Henry's law is one of the gas laws states that: at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is **directly proportional** to the **partial pressure** of that gas in equilibrium with that liquid. * O2 content ∝ PO2 and solubility

Answer 151

Protein composed of 4 aa subunits called Globin (2 alpha and 2 beta) and 4 Heme groups

Answer 152

* What is a heme group? * porphyrin ring structure in which an iron atom binds to oxygen * each heme binds a molecule of oxygen = 4O2 molecules/Hb * What is it called when it's bound to oxygen? Unbound? * Bound * Oxyhemoglobin * No O2 bound * deoxyhemoglobin * Interaction between O2 and hemoglobin is reversible and is strongly influenced by the arterial partial pressure of O2

Answer 153

The interaction between hemoglobin and the arterial PO2

Answer 154

When bood exits the pulmonary capillaries, the percentage of hemoglobin saturation is _100%_

Answer 155

At rest, when blood moves back in the venous system it has _70_% O2 attached to Hb. What does this indicate? * The amount of O2 unloaded in the tissue capillary is minimal at rest

Answer 156

The amount of O2 that can be combined with Hb

Answer 157

How much Hb is present in the blood •change in amount of Hb will change O2 capacity

Answer 158

The percentage of available hemoglobin binding sites that have O2 attached * tells us very little about the O2 capacity

Answer 159

1. Arterial PO2 * MOST important * As PO2 changes, the percentage of Hb saturation changes 2. pH in blood 3. PCO2 4. Temperature

Answer 160

* Hb-O2 dissociation curve is *sigmoidal* * because of cooperative binding

Answer 161

Cooperative binding occurs due to the fact that we have deoxyhemoglobin * First molecule of O2 interacts with heme group and changes the conformation of the heme group and the globin chains * globin chains change conformation from tens to relaxed * Next o2 will attach much easier * causes sigmoidal shape of Hb-O2 binding curve

Answer 162

Because PO2 is necessary to drive diffusion of O2 from RBC to blood to cells and mitochondria

Answer 163

During a high metabolic rate when peripheral tissue is using a lot of O2

Answer 164

Changes in Hb concentration can change oxygen concentration or oxygen capacity without affecting the _Hb saturation_

Answer 165

1. Hb at 10gm/100ml - **low Hb (anemia)** 2. Hb at 15 gm/100ml of blood - Normal 3. Hb at 20gm/100ml of blood - High Hb **polycythemia** * If the hemoglobin is fully functional it will still be able to bind to O2 and therefore the sigmoidal curve will not be affected * At a high PO2 level (120mmHg) 100% of Hb saturation is seen with 10, 15 or 20 * y axis shows how much O2 can be transported * very different with differing [Hb] * Curve showing Hb at 10 has a lower [O2] in the blood compared to the curves with higher [Hb].

Answer 166

CO (carbon monoxide) has 200x the binding affinity for Hb compared to o2 * Reduce O2-Hb binding * Confomational change * Less O2 delivered to peripheral tissue * Harder to unload O2

Answer 167

* Alveolar space has a high PO2 just before the diffusion process (higher than the PO2 in the plasma) * Pressure gradient between plasma and alveoli pulls O2 across the respiratory membrane and into the plasma * Another pressure gradient between the plasma and the inside of the RBC * O2 will move from plasma into RBC where they will bind with Hb according to the **Hb oxygen dissociation curve**

Answer 168

* Capillary is next to a peripheral tissue * Peripheral tissue is composed of tissue cells surrounded by interstitial fluid (IF) * Peripheral tissue cells consume O2 for metabolism * O2 moves from RBC → plasma → IF →space between cells → intracellular space → MIT * oxygen use by MIT creates pressure gradients * Low PO2 in plasma will recall o2 from inside RBC

Answer 169

Major factor: arterial PO2 Other factors: 1. Temperature * ↑ temp → ↑ O2 unloading 2. pH * ↓pH → ↑ O2 unloading 3. pCO2 * ↑PCO2 → ↑ O2 unloading

Answer 170

* Dissolved (5%) * Bicarbonate (HCO3: 60-65%) * Carbamino compounds (25-30%)

Answer 171

In RBC: 1. CO2 + H2O → H2CO3 * Extremely fast reaction 2. Carbonic acid dissociates into H+ and bicarbonate: * H2CO3 → H+ + HCO3

Answer 172

RBC's exchange bicarbonate for _Cl-_ using: the anion exchange protein * Chloride shift * Bicarbonate exits the RBC into the plasma; Cl- moves into RBC to maintain electrical neutrality

Answer 173

Maintain electrical neutrality in the RBC's as bicarbonate leaves the RBC

Answer 174

H+ will increase in venous blood = decrease pH but maintains electrical neutrality

Answer 175

CO2 interacts with the globin chain of hemoglobin to form a carbamino compound called _carbaminohemoglobin_ Hb + CO2 ⇔ HbCO2 No enzyme required

Answer 176

deoxyhemoglobin * CO2 will bind deoxyhemoglobin and shift equilibrium towards a more dissociated hemoglobin-o2 molecule * If PCO2 increases, the O2 dissociation curve shifts to the right = lower %O2 bound to Hb * increased O2 unloading because CO2 will bind preferentially to deoxyhemoglobin

Answer 177

1. Unloading of O2 * lower pH = reduced % Hb saturation = increased O2 unloading 2. Hemoglobin buffers the change in pH at the level of venous blood

Answer 178

**hypoventilation** (CO2 production \> CO2 elimination): Increase PCO2 and Increase H+ concentration

Answer 179

Hyperventilation ( CO2 Production \< CO2 elimination): ↓PCO2 and ↓H+ (increase pH)

Answer 180

↑ in blood H+ concentration independent from changes in PCO2

Answer 181

↓ in blood H+ concentration independent from changes in PCO2

Answer 182

neural control of breathing is established in the _central nervous system_ * Drives inspiratory and expiratory muscles

Answer 183

1. pontine respiratory group 2. dorsal respiratory group 3. ventral respiratory group

Answer 184

Ventral respiratory group Contains both the inspiratory rhythm generator and the expiratory rhythm generator

Answer 185

Breathing is * initiated in the _medulla_ by _specialized neurons_ * Modified by _higher structures of the CNS and inputs from central and peripheral **chemoreceptors** and **mechanoreceptors** in the lung and chest wall_

Answer 186

_PreBötC_ and _pFRG_ neurons drive activity in premotor neurons which excite motorneurons that activate rhythmically respiratory muscles

Answer 187

* Fundamental for generating rhythm which is produced by several factors * Neuromodulatory factors (NT's) * Suprapontine influences that are volitional or emotional * Sensory inputs can also influence the rhythm of breathing

Answer 188

Pre-Bötzinger complex

Answer 189

Peripheral and central chemoreceptors - provide an exctiatory drive to brain centres that control the respiratory group (Dorsal and Ventral respiratory group in medulla)

Answer 190

Hypoxia (low PO2), Hypercapnia (high PCO2) and acidosis all cause an _increase_ in _ventilation_

Answer 191

Carotid and aortic bodies

Answer 192

mainly changes in arterial PO2 and will be activated by changes in pH Sense primarily hypoxia (low arterial PO2)

Answer 193

Type 1 glomus cell: chemosensitive - drive response to change in arterial PO2 Type II sustentacular cells: supporting cells

Answer 194

neurons * -voltage gated ion channels * generate AP's following depolarization * Vesicles with NT's * excite the terminals of the glossopharyngeal afferents * Increase respiratory drive = increase ventilation

Answer 195

specialized neurons located close to the ventral surface of the medulla (close contact with blood vessels and CSF)

Answer 196

Central chemoreceptor pathway - responsible for 70% of the response to hypercapnia - mediated by effects at the level of the dorsal and ventral respiratory groups that change ventilation