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Vanders Human Physiology (PHYSL 210) > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

What are 6 functions of the Respiratory System?

A
  1. Provide O2 and eliminate CO2 (homeostatic regulation of blood gases)
  2. Protect against microbial infection (filter)
  3. Regulate blood pH (with kidney)
  4. Contribute to phonoation (passage of air through vocal cords = speech)
  5. Contributes to olfaction
  6. Reservoir for blood
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2
Q

What is the fundamental unit of the respiratory system?

A

Alveoli

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3
Q

The alveoli are embedded in a dense network and tissue characterized by: _______, ________, and ________ with a large number of _______

A

The alveoli are embedded in a dense network and tissue characterized by: smooth muscle tissue, smooth muscle cells and connectie tissue with a large number of capillaries

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4
Q

What is the passage of air in the upper respiratory tract?

A

Larynx -> trachea -> two primary bronchi -> lungs

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5
Q

How are the trachea and primary bronchi structurally similar?

A

Both are semi-cartilaginous

  • C-shaped ring (made of cartilage) in front and smooth muscle in the back
  • Provides protection for the airway and gives elasticity
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6
Q

How is the structure of the bronchi different from the trachea and primary bronchi?

A
  • Still have cartilaginoous structures but the air pathways are no longer C-shaped
    • C-shaped rings of cartilage are replaced by plates of cartliage and smooth muscle
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7
Q

What provides the structure for bronchioles (prevents collapse)?

A

Smooth muscle (No cartlage)

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8
Q

What are the two regions of the tracheobronchial tree?

A
  1. Conducting zone
    • no alveoli = no gas exchange
    • “anatomical dead space”
  2. Respiratory zone
    • contains alveoli = gas exchange
    • Respiratory bronchioles, alveolar ducts and alveolar sacs
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9
Q

Why is the conducting zone of the tracheobronchial tree called “anatomical dead space”?

What structures are included in this region?

A

Because there are no alveoli therefore no gas exchange occurs.

  • trachea, primary bronchi, bronchioles and terminal bronchioles
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10
Q

What structures are included in the respiratory zone?

A

Respiratory bronchioles, alveolar ducts, and alveolar sacs

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11
Q

What are the smallest airways without alveoli?

A

Terminal bronchioles

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12
Q

What airway structure has sparse, occasional alveoli?

A

Respiratory bronchioles

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13
Q

What are alveoli? How does the amount of blood in contact with alveoli change?

A
  • Tiny sacs with a very thin wall
  • Highly vascularised - many capillaries that contact the alveolar surface
  • Amount of blood in capillaries is variable and changes with metabolic demand
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14
Q

What are type 1 alveolar cells?

A
  • Flat epithelial cells
  • Internal surface of the alveoli is lined with liquid that contains a surfactant
  • Do not divide - susceptible to inhaled or aspirated toxins
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15
Q

Why is surfactant important?

A

For stabalization of the alveolar sac

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16
Q

What are two functions of Type II Alveolar cells?

A
  • Not as common as type one
  • Functions:
    1. Produce the surfactant
    2. Act as a progenitor - have the ability to replicate and differentiate into Type I Alveolar cells
      • potential for fixing damaged alveoli
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17
Q

Oxygen and carbon dioxide diffuse through the _________ in less than _____second(s)

A

Respiratory membrane in less than 1 second

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18
Q

What is the respiratory membrane?

A

Very thin respiratory surface composed of the alveolar epithelial cell (Type I) and the pulmonary capillary endothelial cell

  • Alveolar fluid (w/ surfactant)
  • Alveolar epithelium
  • Basement membrane of alveolar epithelium
  • Interstitial space
  • Basement membrane of capillary endothelium
  • capillary endothelium
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19
Q

What are the five steps of respiration?

A
  1. Ventilation
  2. Exchange of CO2 and O2 btwn alveoli and blood
  3. Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow
  4. Exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues via diffusion
  5. Cellular utilization of O2 and production of CO2
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20
Q

What is ventilation?

A

First step of repiration:

  • Consists of movement of the gas from the atmosphere to the alveoli by bulk flow, independent of the gas composition
    • movement is generated due to changes in volume and pressure that will promote movement from areas of high pressure to areas of low pressure
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21
Q

Where does step two of respiration occur:

“Exchange of O2 and CO2 between the alveoli and the blood system via diffusion”

A
  • Occurs at the level of the respiratory membrane due to changes in pressure of O2 and CO2 between the alveoli and the blood
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22
Q

How is O2 driven into the tissue cells and CO2 out?

A
  • Differential pressure between the blood and the peripheral tissue will drive oxygen from the blood to the peripheral tissue and CO2 will move from the peripheral tissue to the blood to be eliminated
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23
Q

How is Ventilation produced?

A
  • CNS sends an excitatory drive to respiratory motor neurons that innervate the respiratory muscles
  • Respiratory muscles contract
  • Changes the thoracic volume, the thoracic pressure and intrapulmonary pressures
    • These changes involving pressure allow for gas movement
  • Air flows in and out with the different muscle contraction and relaxations
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24
Q

What are the three categories of muscles involved in respiration?

A
  1. Pump muscles
    • inspiratory and expiratory
    • change pressure and volume and level of lungs
  2. Airway muscles
    • keep airways open
  3. Acessory muscles
    • facilitate respiration during forced breathing
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25
Q

What is the most important muscle for respiration?

A

The diaphragm

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26
Q

How does the diaphragm participate in respiration?

A
  • 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
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27
Q

How do the external intercostals participate in breathing?

To which of the three respiratory muscle groups do they belong?

A
  • 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
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28
Q

How do the parasternal intercostals contribute to breathing?

To which of the three respiratory muscle categories do these muscles belong?

A
  • Inspiratory Pump muscle
  • Contract and pull sternum forward - increases anterior posterior dimension of the rib cage
  • Pump handle motion
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29
Q

How do the abdominals contribute to breathing?

To which category of respiratory muscle do they belong?

A
  • Expiratory pump muscles
  • Contraction forces lung to return to resting position
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30
Q

How do the internal intercostals contribute to breathing?

To which category of respiratory muscles do they belong?

A
  • 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
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31
Q

How do the accessory muscles contribute to breathing?

A
  • Scalenes, sternocleidomastoid, and pectoralis minor
  • Not commonly active during resting breathing; active during exercise and forced respiration
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32
Q

What are the inspiratory pump muscles?

A
  1. Diaphragm
  2. External intercostals
  3. Parasternal intercostals
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33
Q

What are the expiratory pump muscles?

A
  1. Abdominals
  2. Internal intercostals
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34
Q

Describe what happens during inspiration at rest (ie quiet breathing)

A
  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
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35
Q

How does inspiration change during forced breathing?

A

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

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36
Q

What happens during quiet expiration?

A
  • No active contraction
  • Relaxation of the inspiratory muscles (diaphragm, external and parasternal intercostals)
  • Air moves out because of lung recoil
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37
Q

How does expiration change during forced breathing?

A
  • 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
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38
Q

What is obstructive sleep apnea?

A
  • 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
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39
Q

What causes obstructive sleep apnea?

A
  • 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
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40
Q

What regions of the respiratory tract are involved in filtering?

A
  • respiratory zone and at the level of the alveoli
  • At conducting zone = muco-ciliary escalator
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41
Q

The filtering action that occurs in the conducting zone of the Respiratory tract is called the _______

A

Muco-ciliary escalator:

  • Two types of cells lining the surface of the trachea:
    • Goblet Cells - produce mucus
    • Ciliated Cells - have cilia on apical surface
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42
Q

What are the components of the muco-ciliary escalator in the conducting airway?

A

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

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43
Q

What fluid is produced by ciliated cells in the conducting zone and why is it important?

A
  • Periciliary fluid
    • Quite liquid (low density)
    • Sits on top of the ciliated cells = sol layer
    • Allows cilia to move freely because of low density
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44
Q

What do the goblet cells in the conducting zone produce?

A

Thick, dense mucus = Gel layer

  • Sparse
  • trap particulates that enter the resp system during inhalation
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45
Q

What cells produce the SOL layer and what cells produce the gel layer?

A

SOL Layer = periciliary fluid from ciliated cells

Gel Layer = mucus from goblet cell

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46
Q

Once particulates are trapped in the mucus, how are they removed from the resp tract?

A

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
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47
Q

What is responsible for the filtering that occurs at the level of the alveoli?

A

Macrophages in the alveoli

-phagocytose particulates and digest them

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48
Q

What is the result of inhaling silica dust or asbestos?

A
  • 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
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49
Q

What is spirometry?

A

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

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50
Q

Define tidal volume

A

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

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51
Q

Define expiratory reserve volume

How is it assessed?

A

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
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52
Q

Define Inspiratory Reserve Volume

A

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

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53
Q

What is residual volume?

Can it be measured with spirometry?

A

The volume of air remaining in the lungs after a maximal expiration; it cannot be expired no matter how vigorous or long the effort

RV cannot be measured with a spirometry test

RV= FRC-ERV

(FRC: functional residual capacity

ERV: expiratory reserve volume

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54
Q

How do you calculate Residual Volume (RV)?

A

RV = (FRC-ERV)

FRC: functional residual capacity

ERV: Expiratory reserve volume

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55
Q

Why is in important that there is always a small volume of air in the lungs (eg the residual volume)

A

Prevents collapse of the alveoli (Atelectasis)

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56
Q

Capacities are measurements of lung ________ and correspond to the sum of:

A

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

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57
Q

What is Vital Capacity?

How is it calculated?

A

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

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58
Q

What is inspiratory capacity?

How is it calculated?

A
  • Inspiratory capacity is the maximal volume of air that can be forcibly inhaled
  • IC = TV + IRV

TV= Tidal Volume

IRV = Inspiratory Reserve Volume

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59
Q

What is the Functional Residual Capacity (FRC)?

How is it calculated?

A
  • 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

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60
Q

What is the Total Lung Capacity (TLC)?

How is it calculated?

A
  • Volume of air in the lungs at the end of a Maximal Inspiration
  • TLC = FRC + TV + IRV = VC +RV
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61
Q

What measurements cannot be determined using spirometry?

A

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

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62
Q

What is the tidal volume in a healthy adult?

A

500mL

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

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63
Q

What is total or minute ventilation?

How is it calculated?

A

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)

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64
Q

What is alveolar ventilation?

How is it calculated?

How will it compare to minute ventilation?

A

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:
  • VA= (TV - VADS) (Resp. Freq)
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65
Q

Tidal volume (air that enters the resp system) is ______mL and conducting airways have a volume of about _____mL (volume of air that is leftover from previous breath; no gas exchange).

What does this mean?

A

Tidal volume (air that enters the resp system) is 500mL and conducting airways have a volume of about 150mL (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

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66
Q

How do we improve alveoli ventilation?

A

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

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67
Q

Spirometry is used to determine the ________ in ____ second(s) and the forced __________

A

Spirometry is used to determine the forced expiratory volume in 1 second(s) and the forced vital capacity

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68
Q

What two volumes can be determined from Spirometry?

A
  1. Forced expiratory volume in 1 second (FEV-1)
  2. Forced vital capacity (FVC)
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69
Q

What is FEV-1

A

Forced Expiratory Volume in 1 second:

  • forced expiratory volume is how much of the vital capacity volume that can be expelled in one second
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70
Q

Forced vital capacity is about _______ in a healthy person

A

Forced vital capacity is about 5 Litres in a healthy person

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71
Q

What can a spirometry test diagnose?

A

Obstructive disease or restrictive disease

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72
Q

Patients affected by obstructive lung disease have shortness of breath due to difficulty in ______ because of ________

A

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

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73
Q

What would a spirometry test show in a patient with Obstructive Lung Disease?

A
  • 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)
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74
Q

What is restrictive lung disease?

A
  • 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
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75
Q

What would a spirometry show that would indicate restrictive lung disease?

A
  • 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
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76
Q

What method can be used to measure the functional residual capacity?

A

Recall: FRC = is the volume remaining in the lungs after a normal, passive exhalation

Can be measured with Helium dilution method

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77
Q

What are the static properties of the lung?

Why are they necessary?

A
  • 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 (PIP),
    • transpulmonary pressure (PPT),
    • static compliance of the lung and
    • surface tension of the lung
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78
Q

What are the dynamic properties of the lung?

A
  • 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
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79
Q

The exchange of air between the atmosphere and the alveoli is:

A

Ventilation

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80
Q

What causes ventilation to occur?

A

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

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81
Q

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

A

In ventilation, air flows by bulk flow from a region of higher pressure to a region of lower pressure

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82
Q

What is Boyle’s law?

A

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

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83
Q

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

A

During the expiratory phase of the lungs, a reduction in volume will generate an increase in alveolar pressure

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84
Q

What is the equation for flow?

A

Flow = ΔP/R

ΔP = Change in pressure (difference in pressure between the alveolar pressure and atmospheric pressure)

R = Resistance

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85
Q

Lungs have a tendency to collapse due to _____

A

Lungs have a tendency to collapse due to elastic recoil

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86
Q

During inspiration and expiration air moves in and out of the lungs due to variation of the:

A
  • Intrapleural pressure - Pressure that is inside the pleura
    • acts like a vacuum
  • Alveolar pressure (PALV)
  • Transpulmonary pressure (PTP) - derived from the difference of the alveolar pressure minus the intrapleural pressure
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87
Q

Because the intrapleural space acts as a relative vacuum, the intrapleural pressure is _________\_

A

Because the intrapleural space acts as a relative vacuum, the intrapleural pressure is älways negative

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88
Q
  • Intrapleural pressure fluctuates with breathing but it is always _______ due to:
  • What would result if the PIP = PALV
A
  • 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
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89
Q

__________ is the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall

A

Transpulmonary Pressure (PTP) is the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall

90
Q

P__ should always be > than P___ in order to maintain the lungs expanded in the thorax

A

P_alv _should always be > than P<u>IP</u> in order to maintain the lungs expanded in the thorax

91
Q

P__ is a static parameter which does not cause airflow, but determines lung volume (VL)

A

P<u>TP</u> is a static parameter which does not cause airflow, but determines lung volume (VL)

92
Q

P__ is a dynamic component that determines air flow

A

P<u>ALV</u> is a dynamic component that determines air flow

93
Q

During an inspiratory effort:

  • CNS sends an _______ to the muscles of inspiration (_____, ______ and ________)
  • Muscles contract and generate an ______ in thoracic volume
  • Intraplueral pressure _______
  • Transpulmonary pressure ________
  • Lung volume _______
  • Alveoli pressure _______
  • generates movement of _____ from low _____ to high _____
A

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
94
Q

Expiration:

  • Relaxation of the ______\_ muscles →
  • chest wall ______\_ (goes back to its resting state) →
  • ______\_ 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 ______\_ as the intrapleural pressure returns to pre-inspiratory values →
  • as transpulmonary pressure is also linked to lung volume, ______\_and a reduce ______\_, generating ______\_ of the gas molecules inside the alveoli →
  • increase in ______\_ so it is greater than the atmospheric pressure →
  • air will move from a region of high ______\_to a region of low ______\_, flowing out of the lungs to the environment
A

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
95
Q

Lungs are embedded inside the pleural tissue called: _______

The inside of the chest wall is lined by another pleural tissue called the ________

A

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

96
Q

What forces can affect resistance to air flow?

A
  • 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
97
Q

Airflow resistance is most sensitive to changes in radius when flow is ______

A

Airflow resistance is most sensitive to changes in radius when flow is NOT laminar (turbulent)

98
Q

What is transitional airflow and where would you likely see it?

A

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
99
Q

Where would you find turbulent flow?

A

In larger airways, such as the trachea, the larynx and the pharynx

  • larger diameter = velocity of gas molecules is higher resulting in turbulent flow
100
Q

What law is used to determine airflow resistance?

A

Poiseuille’s Law

R=(8ηL)/(πr4)

n=viscosity

L = length

*Based on this formula, as the radius is reduced, the resistance will dramatically increase*

101
Q

How do you determine the resistance for branched airways arranged in series vs in parallel?

A
  • 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
102
Q

Why are small airways the most important in pathological conditions?

A

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
103
Q

What are three ways that small airways can be occluded?

A
  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
104
Q

Why can lung compliance be determined both as a dynamic property and a static property?

A

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

105
Q

What is lung compliance?

A

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
106
Q

What is static compliance of the lung?

How is it measured?

A
  • 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
107
Q

What effect on lung compliance does pulmonary fibrosis have?

A
  • 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)
108
Q

How does emphysema affect lung compliance?

A
  • 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
109
Q

What is dynamic compliance of the lung?

A
  • 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
110
Q

Compare dynamic compliance and static compliance

A

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
111
Q

At functional residual capacity (FRC) what will the compliance graphs look like?

A

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

112
Q

In the image we see that the curve for Deflation is different from the curve for inflation, what is this difference defined by?

A

Hysteresis

113
Q

What events do the numbers on the graph represent?

  1. _______
    • at low lung volumes it’s difficult to __________ therefore rising ____ has little effect on _____
  2. ________
    • First increases in ____ reflect the popping open of the ______ followed by their expansion and recruitment of others as air flows into the _______ which progressively increases the ______
  3. ________
    • When all airways are open, making ____ more negative by chest wall expansion inflates the lungs and increases _____ in a linear fashion
    • ______ will expand until basically the _____ properties of the lungs do not allow further expansion
  4. _________
    • Curve reaches a plateau as it reaches the ______ of _________
    • At high _____ lung compliance ______
A

What events do the numbers on the graph represent?

  1. Stable VL
    • 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 PTP has little effect on VL
  2. Opening of airways
    • First increases in VL 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 PTP
  3. Linear expansion of open airways
    • When all airways are open, making PIP more negative by chest wall expansion inflates the lungs and increases VL 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 VL lung compliance decreases
114
Q

What is hysteresis?

A

Difference between the inflation and deflation compliance pathway

(Where compliance is measured as the slope of transpulmonary pressure (x)/Lung volume graph (y))

C= ∆VL / ∆PTP

115
Q

Why does hysteresis exist?

A

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
116
Q

What are two factors that determine lung compliance?

A
  • 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
117
Q

Elastin and collagen are localized in ________, around ______ and ______

  • Influence:
  • Dynamic:
A

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
118
Q

What is it about Elastin and Collagen that affects lung compliance (elasticity)?

What does each protein influence?

A
  • 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 PTP to inflate lung at low volumes
119
Q

What does the image show?†

A
  • 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)
120
Q

What is surface tension and how does it contribute to lung compliance?

A

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
121
Q

Surface tension is a property of:

A

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

122
Q

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

A

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

Hydrogen bonding of water molecules

123
Q

The image shows the importance of surface tension using a P-V curve in which surface tension is eliminated with saline-filled lung. Explain.

A

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
124
Q

What is the relationship between type I alveolar cells and surface tension?

A
  • 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
125
Q

As air enters the lungs it is humidified and saturated with water vapour at body temperature so that when it reaches the alveoli, it means that _________

A

Water molecules cover the alveolar surface creating substantial surface tension

= reduces the volume of the ideal sphere (or alveoli)

126
Q

What is Laplace’s equation?

A

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
127
Q

Does a large alveoli or small alveoli require more pressure to stay open?

A

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

128
Q

Because of surface tension and Laplaces eqn, logic states that smaller alveoli would collapse into larger alveoli. Why does this not occur in physiology?

A

Because of surfactant

  • reduces surface tension at alveoli
  • makes alveoli stable against collapse
129
Q

What produces surfactant?

A

type ii alveolar cells

(ie type ii pneumocytes)

130
Q

What are 4 functions of surfactant?

A
  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
131
Q

Surfactant is a mixture of ________

A

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 *
132
Q

How are alveoli stabilized by surfactant?

What is the importance of the T/r between large and small alveoli (Surface tension/radius ratio)?

A
  • 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
133
Q

What happens when surfactant is more concentrated on the surface of the alveoli? Where would we see this situation?

A

you will have lower surface tension as seen in smaller alveoli

134
Q

Why is it important that surfactant is dynamic?

A

Allows the alveolar tension to change with inflation and deflation

  • thickness of the surfactant layer varies inversely with the surface area
135
Q

Why do premature babies have difficulty with breathing?

A

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

136
Q

Surfactant improves _______ and stabalizes _______

A

Surfactant improves compliance and stabalizes alveolar size

137
Q

What did the inhalation test with radioactive xenon show? What conclusion can be drawn from this?

A

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
138
Q

How do we explain the difference in ventilation between different regions of the lungs?

A
  • There is negative pressure in the intrapleural space (subatmospheric) which changes between the top and bottom of the lung
    • PIP is much more negative at the top of the lung than the bottom
    • PIP 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 = PIP less negative (increase) at the bottom and decrease (more negative) at the top
139
Q

Why do alveoli at the bottom of the lung have an advantage during inhalation?

A
  • 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 PIP will generate large changes in VL

140
Q

What is Dalton’s Law?

A

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

141
Q

Gas exchange occurs at the level of the ____________ (very thin layer of tissue)

A

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
142
Q

What is Fick’s Law?

A

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

Vgas = (A÷T) • D • (P1-P2)

143
Q

The diffusion constant (in ______ law) is proportional to the _________ and inversely proportional to ________

Conclusion?

A

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
144
Q

Which gas diffuses faster between CO2 and O2? Why?

A

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

145
Q

What is Henry’s Law?

A

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

146
Q

The concentration of gas in a liquid is determined by:

A

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)

147
Q

PP of water is variable and depends on __________

A

PP of water is variable and depends on how saturated the air is

148
Q

At the level of the alveoli:

  • PPO2 is ______
  • PPCO2 is _____
A

At the level of the alveoli:

  • PPO2 is reduced
  • PPCO2 is increased
149
Q

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 ___\_and ___\_ returns to the lung capillaries available for the gas exchange
    • PO2 in the atmosphere is ____ mmHg; PO2 at the level of the alveoli is ___\_ mmHg
    • When the mixed venous blood enters the pulmonary circulation, PO2 is ___\_ mmHg (________________)
      • The diffusion process from the alveoli to the lung capillaries is very fast and _______________________\_
      • Blood exiting the lung is equivalent to the gas that is present at the level of the ___\_
    • PO2 in blood exiting the pulmonary capillaries is 100 mmHg (similar to 105 mmHg seen in the alveoli)
A

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)
150
Q

Why is PO2 in the alveoli (105 mmHg) not the same as PO2 in the atmosphere (160 mmHg)? (3)

A
  • 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
151
Q

What 4 factors determine the alveolar PO2?

A
  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
152
Q

What are four determinants of alveolar PCO2?

A
  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
153
Q

Increasing alveolar ventilation (VA) will increase alveolar P____ and decrease alveolar P__

  • Why?
A

Increasing alveolar ventilation (VA) will increase alveolar PO2 and decrease alveolar PCO2

  • 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
154
Q

What will happen if alveolar ventilation is reduced?

A

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

155
Q

What determines arterial levels of PP gas

A

PP of gas in alveoli determines arterial levels

156
Q

Why do we need pulmonary circulation to be low pressure?

A

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

157
Q

Why is pulmonary circulation a low resistance system? What law defines this resistance?

A

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
158
Q

What does it mean when we say that the pulmonary circulation system is high compliance?

A
  • 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
159
Q

The pulmonary system is _____ pressure, ____ resistance, and ______ compliance

A

The pulmonary system is low pressure, low resistance, and high compliance

160
Q

Is the flow in the pulmonary circulatory system more or less than the flow in the systemic circulatory system?

A

They are equal

161
Q

Alveolar capillaries are collapsible, what does this mean?

A

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

162
Q

What is the ventilation-perfusion relationship for respiration/circulation?

A

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)

163
Q

The ratio between ventilation and perfusion is one of the major factors affecting:

A

Alveolar (and therefore arterial) levels of O2 and CO2

164
Q

The greater the ventilation:

A

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

165
Q

The greater the perfusion:

A

The more closely the composition of local alveolar air approaches that of mixed venous blood

(reduced PO2 and increased PCO2)

166
Q

Under what conditions would we see a high ventilation/perfusion ratio?

What is the result in terms of alveolar PO2 and PCO2

A
  • 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
167
Q

Under what conditions might you see a low Ventilation/perfusion (V/Q) ratio? How would this affect alveolar PCO2 and PO2

A
  • 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
168
Q

What is a pulmonary shunt?

A

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
169
Q

Both ________\_and ______\_ decrease from the bottom of the lungs to the top of the lungs

  • The ______ of the two lines representing perfusion and ventilation is different
  • This leads to the ventilation/perfusion ratio being ____\_at the bottom of the lungs and _____\_ at the top of the lungs
A

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
170
Q

Homeostatic mechanisms exist to limit ______ between ventilation and perfusion

A

Homeostatic mechanisms exist to limit mismatch between ventilation and perfusion

171
Q

How do pulmonary capillaries respond to low O2?

A
  • 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
172
Q

What is Pulmonary hypoxic vasoconstriction?

A

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

173
Q

What is the homeostatic response to low blood flow (decreased perfusion) and low airflow (decreased ventilation)?

A
174
Q

In what two forms is O2 carried in the blood?

A
  1. Dissolved in plasma (~2% - O2 has low solubility)
  2. Combined with hemoglobin (~98%)
175
Q

Dissolved O2 follows ________ Law

A

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
176
Q

What is the composition of hemoglobin ?

A

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

177
Q

What is a heme group?

What is it called when it’s bound to oxygen? Unbound?

A
  • 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
178
Q

What does an oxygen dissociation curve show?

A

The interaction between hemoglobin and the arterial PO2

179
Q

When bood exits the pulmonary capillaries, the percentage of hemoglobin saturation is _______

A

When bood exits the pulmonary capillaries, the percentage of hemoglobin saturation is 100%

180
Q

At rest, when blood moves back in the venous system it has ____% O2 attached to Hb. What does this indicate?

A

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
181
Q

What is oxygen capacity?

A

The amount of O2 that can be combined with Hb

182
Q

What does O2 Capacity depend on?

A

How much Hb is present in the blood

•change in amount of Hb will change O2 capacity

183
Q

What is Hemoglobin Saturation?

What does it tell us about O2 capacity?

A

The percentage of available hemoglobin binding sites that have O2 attached

  • tells us very little about the O2 capacity
184
Q

What four factors can influence the interaction between Hemoglobin and oxygen (Hb saturation)?

A
  1. Arterial PO2
    • MOST important
    • As PO2 changes, the percentage of Hb saturation changes
  2. pH in blood
  3. PCO2
  4. Temperature
185
Q

Why is the Hb-O2 dissociation cure not linear?

A
  • Hb-O2 dissociation curve is sigmoidal
  • because of cooperative binding
186
Q

What is cooperative binding and why does it occur?

A

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
187
Q

Why is it important that PO2 remains relatively high in capillary of peripheral tissue?

A

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

188
Q

In what situation would PO2 go below 40 mmHg?

A

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

189
Q

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

A

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

190
Q

What is the difference between the Sigmoidal curves?

A
  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].
191
Q

What is the effect of CO in the respiratory tract?

A

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
192
Q

Describe the diffusion of O2 between the lung and the blood capillary and the pressure gradients that drive it:

A
  • 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
193
Q

Describe the diffusion of O2 between the Blood and the peripheral tissue and the pressure gradients that drive it:

A
  • 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
194
Q

What is the major factor influencing the binding between Hb and O2?

What are 3 other factors that affect the O2 dissociation curve?

A

Major factor: arterial PO2

Other factors:

  1. Temperature
    • ↑ temp → ↑ O2 unloading
  2. pH
    • ↓pH → ↑ O2 unloading
  3. pCO2
    • ↑PCO2 → ↑ O2 unloading
195
Q

In what 3 forms is CO2 carried in the blood?

A
  • Dissolved (5%)
  • Bicarbonate (HCO3: 60-65%)
  • Carbamino compounds (25-30%)
196
Q

How is Carbonic Anhydrase formed in the RBC?

A

In RBC:

  1. CO2 + H2O → H2CO3
    • Extremely fast reaction
  2. Carbonic acid dissociates into H+ and bicarbonate:
    • H2CO3 → H+ + HCO3
197
Q

RBC’s exchange bicarbonate for ____ using:

A

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
198
Q

What is the function of chloride shift?

A

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

199
Q

What change allows for HCO3- to exit the cells?

A

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

200
Q

CO2 interacts with the globin chain of hemoglobin to form a carbamino compound called _______

A

CO2 interacts with the globin chain of hemoglobin to form a carbamino compound called carbaminohemoglobin

Hb + CO2 ⇔ HbCO2

No enzyme required

201
Q

Co2 has a higher affinity for (deoxyhemoglobin or oxyhemoglobin)

A

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
202
Q

What are two effects from the interaction between hemoglobin and H+?

A
  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
203
Q

What is Respiratory acidosis?

A

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

204
Q

What is Respiratory alkalosis?

A

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

205
Q

What causes Metabolic acidosis?

A

↑ in blood H+ concentration independent from changes in PCO2

206
Q

What causes Metabolic Alkalosis?

A

↓ in blood H+ concentration independent from changes in PCO2

207
Q

neural control of breathing is established in the ________

A

neural control of breathing is established in the central nervous system

  • Drives inspiratory and expiratory muscles
208
Q

What are three important regions in the brainstem that control breathing?

A
  1. pontine respiratory group
  2. dorsal respiratory group
  3. ventral respiratory group
209
Q

Which part of the brainstem generates respiratory rates?

A

Ventral respiratory group

Contains both the inspiratory rhythm generator and the expiratory rhythm generator

210
Q

Breathing is

  • initiated in the ______ by ______
  • Modified by ________
A

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
211
Q

______ and _____ neurons drive activity in premotor neurons which excite motorneurons that activate rhythmically respiratory muscles

A

PreBötC and pFRG neurons drive activity in premotor neurons which excite motorneurons that activate rhythmically respiratory muscles

212
Q

What are pre-Bötzinger and parafacial respiratory groups important for?

A
  • 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
213
Q

What excites inspiratory pre-motor neurons in ventral respiratory group which then excite motor neurons and activate the diaphragm and external intercostals

A

Pre-Bötzinger complex

214
Q

Rhythm is generated by the _____

A

pFRG

215
Q

What senses changes in PCO2, PO2 and pH?

A

Peripheral and central chemoreceptors

  • provide an exctiatory drive to brain centres that control the respiratory group (Dorsal and Ventral respiratory group in medulla)
216
Q

Hypoxia, Hypercapnia and acidosis all cause an ______ in _______

A

Hypoxia (low PO2), Hypercapnia (high PCO2) and acidosis all cause an increase in ventilation

217
Q

What are two peripheral chemoreceptors mentioned in lecture>

A

Carotid and aortic bodies

218
Q

Carotid and aortic chemoreceptors sense:

A

mainly changes in arterial PO2 and will be activated by changes in pH

Sense primarily hypoxia (low arterial PO2)

219
Q

What are the 2 cell populations in the carotid bodies?

A

Type 1 glomus cell: chemosensitive - drive response to change in arterial PO2

Type II sustentacular cells: supporting cells

220
Q

glomus cells (in carotid bodies) have characteristics similar to:

A

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
221
Q

what are central chemoreceptors?

A

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

222
Q

Which chemoreceptor pathway is the principle pathway that responds to PCO2 levels

A

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

Vanders Human Physiology (PHYSL 210) (31 decks)

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