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Physiology 210 > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

Functions of the respiratory system

A
  • provides O2 and eliminates CO2
  • protects against microbial infection
  • regulates blood pH
  • contributes to phonation
  • contributes to olfaciton
  • blood reservoir
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2
Q

Upper airway parts

A
  • nasal and oral cavity - air enters
  • pharynx - composed of nasopharynx and laryngopharynx
  • larynx - contains vocal cords
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3
Q

Air passage from larynx to lungs

A

larynx –> trachea –> two primary bronchi –> lungs

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4
Q

Trachea and primary bronchi structure

A
  • semi-cartilaginous
  • C-shaped cartilage ring in front and smooth muscle in back
  • provides protection for airway and gives elasticity
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5
Q

Bronchi

A
  • plates of cartilage and smooth muscle
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6
Q

Bronchioles

A
  • smooth muscle
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7
Q

Conducting zone

A
  • trachea, primary bronchi, bronchioles, terminal bronchioles
  • no alveoli and no gas exchange
  • anatomical dead space
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8
Q

Respiratory zone

A
  • contains the alveoli
  • initially sparse but becomes very numerous with branching
  • respiratory bronchiole –> alveolar ducts –> alveolar sacs
  • gas exchange
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9
Q

Tracheobronchial tree

A
  • each branching is called a generation
  • begin at generation 0 in trachea and goes to generation 23 at alveolar sacs
  • diameter and length decrease
  • number of branches and total surface area increase
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10
Q

Alveoli

A
  • tiny sacs with very thin wall
  • highly vascularized - many capillaries
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11
Q

Type I alveolar cells

A
  • flat epithelial cells
  • internal surface of alveoli is lined with liquid that contains surfactant (stabilization of sac)
  • do not divide
  • susceptible to inhaled or aspirated toxins
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12
Q

Type II alveolar cells

A
  • not found frequently
  • produce surfactant
  • act as progenitor cells - able to replicate and differentiate into Type I alveolar cells
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13
Q

Pneumocyte

A
  • one of the cells lining the alveoli of lung
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14
Q

Steps of respiration

A
  1. ventilation - movement of gas from atmosphere to alveoli by bulk flow
  2. exchange of O2 and CO2 between alveoli and blood system by diffusion
  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 by diffusion
  5. cellular utilization of O2 and production of CO2
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15
Q

How is ventilation produced?

A
  • CNS sends excitatory drive to respiratory motor neurons that innervate respiratory muscles
  • respiratory muscles contract
  • changes thoracic volume and pressure
  • allow for gas movement
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16
Q

3 categories of respiration muscles

A
  • pump muscles
  • airway muscles
  • accessory muscles
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17
Q

Pump muscles

A
  • make changes in pressure and volume at lungs
  • inspiration - diaphragm
  • expiration
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18
Q

Airway muscles

A
  • muscle located at airway level and keep upper airways opens
  • mostly inspiratory, some in expiration
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19
Q

Accessory muscles

A
  • facilitate respiration during exercising, when there is an increased metabolic drive
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20
Q

Diaphragm

A
  • most important muscle for respiration
  • dome-shaped structure and separates lungs and abdominal content
  • when diaphragm contracts, it moves down, allowing abdominal content to be pushed down, and rib cage to be pushed outward
  • increase in thoracic volume when it contracts
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21
Q

External intercostals

A
  • inspiratory pump muscle
  • contract and lift the rib cage
  • lateral increase in thoracic volume
  • bucket handle motion
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22
Q

Parasternal intercostals

A
  • inspiratory pump muscle
    -contract and pull sternum forward
  • anterior and posterior increase of rib cage
  • pump handle motion
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23
Q

Abdominals

A
  • inspiratory pump muscle - active all the time
  • expiratory pump muscle
  • does not contract at rest
  • active when making an effort to breath - stress, exercise, coughing
  • return lung to resting position
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24
Q

Internal intercostals

A
  • expiratory pump muscle
  • relaxed at rest and recruited during forced expiration
  • push rib cage down to reduce amount of air and volume of thoracic cage
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25
Q

Inspiration at rest

A
  • diaphragm, external intercostals, parasternal intercostals
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26
Q

Inspiration when active

A
  • stronger contraction of diaphragm and recruitment of accessory muscles
  • further expanding of thoracic cavity
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27
Q

Expiration at rest

A
  • no muscles are recruited
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28
Q

Expiration when active

A
  • abdominal muscles contract intensely
  • diaphragm is moved even higher and more air is expelled
  • internal intercostals muscles contract and push rib cage down
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29
Q

Obstructive sleep apnea

A
  • upper airway muscle activity is depressed when asleep
  • floppy muscle
  • no airflow resulting in snoring, large drops of oxygen saturation in blood, daytime sleepiness, cognitive impairment, hypertension
  • treatment: mechanical device to send positive airway pressure through nasal
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30
Q

2 cells on trachea surface - muco-ciliary escalator

A
  • goblet cells - sparse, produce mucus, no cilia, GEL layer, very dense fluid, distributed in patches
  • ciliated cells - layer of cells with cilia on apical surface, move continuously, produce SOL layer, very low density fluid
  • entrap inhaled biological and inert particulates and remove from airways
  • cilia move mucus through esophagus
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31
Q

Macrophages in alveoli

A
  • last defense
  • smallest particulates attract the macrophages which phagocytose these particulates, digesting them, and elimination infection
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32
Q

Silica dust and asbestos inhalation

A
  • macrophages can recognize but cannot digest
  • breaks and kills the macrophages causing it to disintegrate and release chemotactic factors
  • promotes fibroblasts and collagen
  • stiff lungs –> pulmonary fibrosis
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33
Q

Spirometry

A
  • test that determines amount and rate of inspired and expired air
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34
Q

Tidal volume

A
  • volume of air moved in or out of the respiratory tract (breathed) during each ventilatory cycle
  • approximately 0.5 L
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35
Q

Expiratory reserve volume

A
  • additional volume of air that can be forcibly exhaled following a normal expiration
  • accessed by expiring maximally to the maximum voluntary expiration
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36
Q

Inspiratory reserve volume

A
  • additional volume of air that can be forcibly inhaled following a normal expiration
  • accessed by inspiring maximally, to the maximum possible inspiration
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37
Q

Residual volume

A
  • volume of air remaining in lungs after maximal expiration
  • cannot be expired no matter what
  • cannot be measured with spirometry test
  • prevents collapsing of alveoli or atelectasis
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38
Q

Vital capacity

A
  • maximal volume of air that can forcibly exhaled after maximal inspiration
  • VC = TV + IRV + ERV
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39
Q

Inspiratory capacity

A
  • maximal volume if air that can be forcibly inhaled
  • IC + TV + IRV
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40
Q

Functional residual capacity

A
  • volume of air remaining in the lungs at the end of normal expiration
  • FRC = RV + ERV
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41
Q

Total lung capacity

A
  • volume of air in the lungs at the end of maximal inspiration
  • TLC = FRC + TV + IRV
  • TLC = VC + RV
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42
Q

Total / minute ventilation

A
  • amount of air that is exchanged within a rate time
    = tidal volume x respiratory frequency
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43
Q

Alveolar ventilation

A
  • amount of air moved into alveoli per minute
  • smaller than minute ventilation because of anatomical dead space, the conducting zone (approximately 0.15 L)
    = (tidal volume - dead space) x respiratory frequency
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44
Q

Volume of anatomic dead space is always ____, ____ from how big a breath you take

A
  • constant; independent
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45
Q

To increase rate of breathing, is it more effective to take a deeper breath or increase beathing rate

A
  • increased depth of breath
  • majority of minute ventilation is dedicated to or available for gas exchange
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46
Q

Forced expiratory volume in 1 second - spirometry test

A
  • patient is asked to make a maximal inspiration and then make an expiratory effort to exhale as much as they can
  • FEV-1 - how much of vital capacity volume that can be expelled in 1 second (healthy person can expel most)
  • FVC - total amount if air is blown out in one breath after max inspiration as fast as possible
  • ratio between FEV-1/FVC represents the proportion of amount of air that is blowing out in 1 second
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47
Q

Obstructive lung disease

A
  • shortness of breath due to difficulty exhaling all air from their lungs
  • abnormally high amount of air still lingering in lungs
  • bronchial asthma, chronic obstructive pulmonary disease or cystic fibrosis
  • FEV-1 is significantly reduced
  • process of expiration is much slower - lower slope
  • FEV-1/FVC is reduced (<0.7)
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48
Q

Restrictive lung disease

A
  • patients cannot fully filly their lungs with air, lungs are restricted from expanding
  • stiffness in lung, stiffness of chest wall, weak muscles, damaged nerves, asbestos, silica dust
  • FVC is reduced
  • FEV-1 is reduced
  • ratio will be similar
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49
Q

Helium dilution method

A
  • spirometer cannot measure air the remains in lungs at the end of forced expiration
  • can measure functional residual capacity
  • helium is an inert gas that is not taken by vascular system but is confined to lungs
  • concentration C2 is measured at the end of expiratory effort
  • V2 = V1 (C1-C2) / C2
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50
Q

Static properties of the lung

A
  • mechanical properties that are present in lungs when no air is flowing
  • necessary to maintain lung and chest wall at certain volume
  • intrapleural pressure, transpulmonary pressure, static compliance, surface tension
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51
Q

Dynamic properties of the lung

A
  • mechanical properties when lungs are changing volume and air is flowing in and out
  • alveolar pressure
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52
Q

Boyle’s law

A
  • fixed amount if gas at constant temperature, the pressure and volume are inversely proportional
  • during expiratory phase, reduce in volume will generate an increase in alveolar pressure
  • during inspiratory phase, increase in volume will generate a decrease in alveolar pressure
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53
Q

Bulk flow

A
  • change in pressure will lead to gas movement from a region that has a high pressure to a region that has low pressure
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54
Q

Pleural tissue

A
  • lung and chest wall is closely connected to a double layer of pleural tissue separated by inreapleural fluid
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55
Q

Visceral pleura

A
  • lines to lungs
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56
Q

Parietal pleura

A
  • inside of chest wall
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57
Q

Elastic recoil of lung and chest walls

A
  • lungs - tendency to collapse
  • chest wall - tendency to expand
  • at equilibrium with each other not by direct attachment but through intrapleural space
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58
Q

Intrapleural pressure (Pip)

A
  • pressure in the pleural cavity
  • acts a relative vacuum
  • always negative (subatmospheric)
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59
Q

Alveolar pressure (Palv)

A
  • pressure of the air inside the alveoli
  • Palv - Patm governs the gas exchange between lungs and atmosphere
  • dynamic element directly producing air flow
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60
Q

Transpulmonary pressure (Ptp)

A
  • responsible for keeping alveoli open, expressed as pressure gradient across alveolar wall
  • Ptp = Palv - Pip
  • static parameter that determines lung volume
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61
Q

Steps of inspiration

A
  • CNS sends excitatory drive to muscles
  • muscles contract and generate increase in thoracic volume
  • intrapleural pressure becomes more negative
  • transpulmonary pressure increases
  • increases in lung volume
  • decrease in alveoli pressure
  • difference in pressure generates movement of gas from atmosphere into alveoli
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62
Q

Steps of expiration

A
  • relaxation of inspiratory muscles
  • chest wall recoils
  • intrapleural pressure moves back
  • transpulmonary pressure decreases
  • decrease in lung volume
  • increase in alveoli pressure
  • movement of gas from alveoli to atmosphere
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63
Q

Forces that affect resistance to air flow

A
  • inertia of respiratory system (minimal)
  • friction forces: between different alveolar sacs, between lungs and chest wall, resistance that airflow incurs when enters the airway (80%)
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64
Q

Laminar airflow

A
  • little resistance
  • linear fashion
  • small airways (terminal bronchioles)
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65
Q

Transitional airflow

A
  • extra energy for resistance increase
  • bronchial tree at ramifications or branches
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66
Q

Turbulent flow

A
  • not smooth and laminar
  • large airways (trachea, larynx, pharynx)
  • high gas velocity
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67
Q

Resistance in first part of conducting zone and respiratory zone?

A

minimal

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68
Q

Are airways arranged in series or parallel

A
  • parallel
  • radius inverse of resistance kinda
  • resistance is minimal in smaller airways
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69
Q

3 ways airways can be occluded

A
  • contraction of surrounding smooth muscle
  • edema (fluid) can reduce space for airflow
  • mucus can reduce alveolar space at bronchioles
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70
Q

Lung compliance

A
  • measure of elastic properties of the lung and measure of how easily the lungs can expand
  • change in lung volume (y-axis) produced by a change in transpulmonary pressure (x-axis)
  • compliance is slope of curve
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71
Q

Static compliance

A
  • when no air is flowing through
  • patient is asked to maximally inspire then expire and take pauses
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72
Q

Pulmonary fibrosis

A
  • low lung compliance
  • stiff lungs
  • overproduction of collagen
  • bigger effort to expand chest wall
  • large change in transpulmonary pressure results in small change in lung volume
  • smaller slope
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73
Q

Emphysema

A
  • high lung compliance
  • floppy lungs
  • small change in transpulmonary pressure results in large change in lung volume
  • bigger slope
  • floppy lungs
  • lost alveolar tissue leading to many spaces and reduction in surface for gas exchange
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74
Q

Dynamic compliance

A
  • periods of gas flow (inspiration or expiration)
  • not just elastic properties but also airway resistance
  • less or equal to static compliance
  • slope falls when lung stiffness or airway resistance increases
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75
Q

Hysteresis

A
  • defines the difference between the inflation and deflation compliance path
  • elastic properties of lung
  • more pressure is needed to open an airway rather than keep open an airway that is already open (balloon)
76
Q

2 factors for lung compliance

A
  • elastic components of the lungs
  • surface tension at air-water interface within alveoli
77
Q

Elastin

A
  • high extensible
  • spring
  • lung stretch
78
Q

Collagen

A
  • low extensible
  • stiffness
79
Q

Surface tension

A
  • makes the lung collapse or gives lungs elastic recoil
  • decreases lung compliance
  • water molecules strongly interact with each other and stick
80
Q

Alveolar surface tension

A
  • air entering lungs is saturated with water vapor and water molecules cover alveolar surface
  • strong attractive forces create a belt action and tighten the belt to reduce surface of sphere
81
Q

The smaller the bubble’s radius the ____ the pressure needed to keep bubble open

A

greater

82
Q

Pressure gradient in alveolar surface tension

A
  • gas present in smaller alveoli will move to large alveoli because of high pressure movement to low pressure
  • smaller alveoli collapses into bigger
  • does not occur because of surfactant
83
Q

Alveolar surfactant

A
  • produced by type II alveolar cells
  • functions to reduce surface tension and alveoli level
  • overall effect is improved lung compliance which allows easier breathing
  • makes alveoli stable against collapse
  • allows alveolar communication
84
Q

Surfactant structure and function

A
  • mixture of phospholipids (hydrophilic head and hydrophobic tail)
  • positioning of surfactant at air water interface breaks strong attractive forces between water molecules
  • there is equal amount of surfactant in different sizes of alveoli
  • more concentrated surfactant –> lower surface area (smaller alveoli)
85
Q

In smaller alveoli, surfactant is found _____.
In large alveoli, surfactant is found _____.

A
  • closer together
  • further apart
86
Q

Infant respiratory distress syndrome

A
  • in premature babies with respiration problems
  • their surfactant has not developed in the lungs and it takes a lot of effort to breath and increase lung volume
  • treatment: administer artificial surfactant
87
Q

Radioactive xenon test and results

A
  • breath in xenon and test radioactive activity
  • ventilation is higher in lower lung zones than the top
  • when lying flat, ventilation highest in the back
  • when handstand, ventilation highest in the top
88
Q

Intrapleural pressure (Pip) is much more ____ at the top of the lung than the bottom

A

negative
- lungs have weight that are affected by gravity
- weight increases pressure which makes intrapleural pressure less negative
- since alveoli at bottom are starting more deflated, they are able to expand more

89
Q

Pressure of gas is dependent on

A
  • temperature
  • concentration of gas molecules
90
Q

Dalton’s Law

A
  • the total pressure of this mixture of gas is given by the sum of the individual pressures
91
Q

Air is composed of

A

oxygen, nitrogen, carbon dioxide, water

92
Q

Percentage of water in inhaled air will ____

A

increase because is it warmed and becomes humidified through nasal and oral cavities

93
Q

Respiratory membrane

A
  • very thin layer of tissue that contains fluid, epithelial cells in the alveoli, interstitial space, and basement membrane
  • thinness is advantageous for gas diffusion
94
Q

Fick’s law

A

rate of transfer of gas:
- proportional to surface area of membrane and different in partial pressure between environments
- inversely proportional to thickness of membrane
- diffusion constant

95
Q

Diffusion constant

A

amount of gas transferred:
- proportional to solubility of gas
- inversely proportional to the square root of molecular weight

96
Q

Is carbon dioxide or oxygen more soluble?

A

carbon dioxide

97
Q

Henry’s Law

A
  • concentration of gas molecules in liquid is proportional to partial pressure of gas which the liquid is in equilibrium
98
Q

At the level of the alveoli, partial pressure of oxygen is _____ and partial pressure of carbon dioxide is _____.

A
  • reduced
  • increased
99
Q

Blood exiting the lung is ____ the gas that is present at the level of alveoli

A

equivalent to

100
Q

Why is PO2 in air of alveoli (105 mmHg) less than the PO2 in the atmosphere (160 mmHg)

A
  • air reaching the alveoli is warmed up and humidified (partial pressure of water will increase and oxygen will decrease)
  • lots of blood available for diffusion or gas exchange
  • mix with air that is in the functional residual capacity
101
Q

Determinants of alveolar PO2

A
  • PO2 in the atmosphere (higher altitudes - PO2 is reduced)
  • alveolar ventilation (increase will result in more air getting exchanged)
  • metabolic rate (exercising will result in lower PO2 in mixed venous blood)
102
Q

Determinants of alveolar PCO2

A
  • PCO2 in the atmosphere (basically zero)
  • alveolar ventilation
  • metabolic rate
  • lung perfusion
103
Q

Increasing alveolar ventilation will ____ alveolar PO2 and ____ alveolar PCO2

A
  • increase
  • decrease
    air will be more similar to air present in atmosphere
    more CO2 will be eliminated
104
Q

Increasing metabolic rate will ____ alveolar PO2 and ____ alveolar PCO2

A
  • increase
  • decrease
105
Q

Pulmonary circulation is a low pressure system because

A
  • respiratory membrane is extremely fragile
  • high blood pressure can damage the respiratory membrane and edema could move into lungs
106
Q

Pulmonary circulation is a low resistance system because

A
  • short wide vessels consistently reduce the resistance of pulmonary circulation
107
Q

Pulmonary circulation is a high compliance system because

A
  • thin-walled vessel
  • small changes in pressure result in large expanion of vessel
108
Q

Why are alveolar capillaries collapsible

A
  • if capillary pressure falls below alveolar pressure, the capillaries close off, diverting blood to other pulmonary capillary beds with higher pressures
109
Q

Ventilation-perfusion relationship

A
  • inspired air must be delivered to regions of the lung where the blood is going
  • balance between ventilation (O2 in and CO2 out) and perfusion (O2 out and CO2 in)
110
Q

The greater the ventilation, the more the PO2 and PCO2 will be similar to

A

atmospheric pressures

111
Q

The greater the perfusion, the more the PO2 and PCO2 will be similar to

A

mixed venous blood

112
Q

Normal optimal ventilation-perfusion ratio

A

PO2 - 100-105 mmHg
PCO2 - 40 mmHg

113
Q

A high ventilation/perfusion ratio

A
  • blood flow is obstructed
  • alveoli are normally ventilated but there is little gas exchange that occurs across respiratory membrane because there is no blood available for gas exchange
  • PO2 at alveoli will be increased because there is no oxygen that passes through lungs
  • PCO2 at alveoli will be decreased because there is no CO2 that is delivered
  • alveolar dead volume
  • region is over-ventilated or under-perfused and does not contribute to gas exchange
114
Q

Alveolar dead volume

A
  • region of lungs where there is high ventilation/perfusion ratio because of a pathological condition
115
Q

A low ventilation/perfusion ratio

A
  • collapsed bronchi or bronchioles
  • no gas exchange between alveolar air and atmosphere
  • PO2 at alveoli will decrease
  • PCO2 at alveoli will increase
  • blood is shunt and passes through system
116
Q

Shunt blood

A
  • portion of venous blood that does not get oxygenated
117
Q

Lung ventilation and lung perfusion are higher at the ____ of the lung

A

base/bottom

118
Q

Blood flow and ventilation ____ from the bottom of the lungs to the top

A

decrease

119
Q

PO2 and PCO2 at bottom of lung

A
  • reduced PO2
  • increased PCO2
  • 0.6 x ideal V/P ratio
120
Q

PO2 and PCO2 at top of lung

A
  • increased PO2
  • reduced PCO2
  • 3 x ideal V/P ratio
121
Q

V/P matching with decreased airflow to lung

A
  • decreased alveolar pressure and decreased PO2
  • decrease PO2 in arterial blood
  • vasoconstriction of pulmonary vessels
  • decreased blood flow
  • local adaptive effect to region of lung to decrease blood flow
  • blood will be diverted to regions where ventilation is still effective
122
Q

V/P matching with decreased blood flow to lung

A
  • increase alveolar PO2 and decrease PCO2
  • bronchoconstriction
  • less air moves into region that has decreased blood flow
  • diversion of blood flow from region that has low ventilation to region of high ventilation
123
Q

Oxygen is carried in 2 forms

A
  • dissolved in plasma - 2%
  • combined with hemoglobin - 98%
124
Q

Hemoglobin structure

A
  • 4 amino acid subunits (2 alpha and 2 beta)
  • 4 Heme groups
  • 4 ferrous irons
125
Q

Hemoglobin bound to oxygen

A

oxyhemoglobin

126
Q

Hemoglobin not bound to oxygen

A

deoxyhemoglobin

127
Q

Oxygen dissociation curve at PO2 = 100 mmHg

A
  • when blood exits the pulmonary capillaries
  • hemoglobin saturation is 100%
128
Q

Oxygen dissociation curve at PO2 = 40 mmHg

A
  • when blood is in the peripheral tissue
  • hemoglobin saturation is 75%
129
Q

When blood moves back in venous system, it has __% of oxygen attached to hemoglobin

A

70%

130
Q

Oxygen capacity

A
  • maximum amount of oxygen that can be combined with hemoglobin
131
Q

Hemoglobin saturation

A
  • percentage of available hemoglobin binding sites that have oxygen attached
132
Q

Determinants of Hb saturation

A
  • arterial PO2 –> most important
  • pH in blood
  • PCO2
  • temperature
133
Q

Oxygen dissociation curve relationship and shape

A

sigmoidal (S shaped)
- due to cooperative binding

134
Q

Cooperative binding

A
  • first molecule of oxygen interacts with heme group
  • changes conformation from tense state to relaxed state
  • next oxygen molecule that binds to Hb will attach easier
  • facilitates binding of next oxygen molecule
135
Q

Regions of oxygen dissociation curve

A
  • flat plateau portion: 60-100 mmHg
  • steep portion: 10-60 mmHg
136
Q

Plateau region - O2 dissociation curve

A
  • reduced alveolar PO2 and therefore arterial PO2
  • saturation stays high over wide range of alveolar PO2
  • provides safety factor so that even significant limitation of lung function will allows normal O2 saturation of Hb
137
Q

Steep portion (10-40 mmHg) - O2 dissociation curve

A
  • increases in metabolic rate cause further decrease in tissue PO2, facilitates diffusion from plasma which leads to drop in plasma PO2
  • diffusion of O2 from RBC and addition dissociation of O2 from Hb
  • exercising muscle can extract much more O2 from blood compared to resting conditions
138
Q

Steep portion (40-60 mmHg) - O2 dissociation curve

A
  • unload large amounts of O2 with only small decrease at PO2
  • important that PO2 remains high in capillary of peripheral tissue since pressure is necessary to drive diffusion of O2 to RBC
  • small changes in pH or temperature enhance O2 unloading
139
Q

Anemia Hb amounts

A

10 mg of Hb/100 ml of blood

140
Q

Normal Hb amounts

A

15 mg of Hb/100 ml of blood

141
Q

Polycythemia Hb amounts

A

20 mg of Hb/100 ml of blood

142
Q

Carbon monoxide

A
  • 200x more affinity for Hb compared to O2 and binds tightly
  • binding of CO will displace oxygen
  • decrease in % of Hb oxygen saturation
  • CO induces a conformational change that will hold O2 more tightly to Hb
  • shift towards left on Hb disassociation curve
  • less oxygen that is delivered to peripheral tissue
143
Q

Oxygen movement in lungs and blood capillary

A
  • alveolar space has high O2 and will diffuse into plasma (pressure gradient)
  • another pressure gradient moves plasma O2 into RBC
  • O2 will bind to Hb according to Hb oxygen dissociation curve
144
Q

Oxygen movement in blood capillary and peripheral tissue

A
  • oxygen moves from RBC to plasma to interstitial fluid to space between cells to intracellular space to mitochondria
  • low PO2 in plasma will call oxygen so oxyhemoglobin and deoxyhemoglobin equilibrium moves towards deoxyhemoglobin (more O2 unloading)
145
Q

What does a shift to the right of the oxygen dissociation curve mean?

A
  • there will be lower % of Hb that has oxygen
  • O2 affinity of Hb is reduced
  • unloading oxygen at peripheral tissue
146
Q

Factors that cause a shift to the right of the oxygen dissociation curve

A
  • increased body temperature
  • increased in PCO2
  • increase H+ production
  • increased body metabolism
  • DPG in RBCs in RBC metabolism
147
Q

CO2 is ____ soluble in water than O2

A

more

148
Q

CO2 is carried in blood in 3 forms

A
  • dissolved 5%
  • bicarbonate 60-65%
  • carbamino compounds 25-30%
149
Q

Carbonate form of CO2 in RBC

A
  • CO2 and H2O are catalyzed by carbonic anhydrase to produce carbonic acid (H2CO3)
  • carbonic acid dissociates into H+ and bicarbonate (HCO3-)
  • anion exchange protein exchanges Cl- into cell and bicarbonate out of cell (chloride shift - electrical neutrality)
150
Q

Carbamino compounds of CO2 in RBC

A
  • CO2 interacts with globin chain of hemoglobin to form carbaminohemoglobin (HbCO2)
  • no enzyme is needed
  • CO2 has higher affinity for deoxyhemoglobin
  • shift O2 dissociation curve to the right
  • increased oxygen unloading
151
Q

Carbon dioxide movement in lungs

A
  • pressure gradient drives CO2 from plasma to alveoli
  • cause more CO2 to move from inside of RBC to plasma
  • bicarbonate will diffuse back into RBC and react with H+ to produce carbonic acid and more CO2
  • hemoglobin is now available for O2
152
Q

Transport of H+ between tissues and lungs

A
  • H+ is produced during HCO3- formation
  • H+ stay inside RBCs and bind to Hb
  • H+ has higher affinity for deoxyhemoglobin that oxyhemoglobin - favor oxygen unloading
153
Q

2 effects of H+ binding with hemoglobin

A
  • unloading of oxygen at low pH
  • buffers the change in pH at the level of venous blood
154
Q

Respiratory acidosis

A
  • hypoventilation - increased CO2 production
  • increased PCO2
  • increased H+
155
Q

Respiratory alkalosis

A
  • hyperventilation - increased CO2 elimination
  • decreased PCO2
  • decreased H+
156
Q

Metabolic acidosis

A
  • increase in blood H+ concentration
  • independent of PCO2
157
Q

Metabolic alkalosis

A
  • decrease in blood H+ concentration
  • independent of PCO2
158
Q

Neural control of breathing is established in the

A

CNS

159
Q

3 regions in the brainstem that control breathing

A
  • pontine
  • dorsal
  • ventral (most important - contains inspiratory and expiratory rhythm generator)
160
Q

Breathing is initiated in the

A

medulla by specialized neurons

161
Q

Breathing is modified by

A

higher structures of the CNS and inputs from central and peripheral chemoreceptors and mechanoreceptors in lungs and chest

162
Q

Pre-Botzinger complex

A
  • inspiratory rhythm generator
  • groups of neurons in the ventral respiratory group
  • polysynaptic pathway - generates excitatory inspiratory activity that excites inspiratory muscles
163
Q

Parafacial respiratory group (pFGR)

A
  • expiratory rhythm generator
  • group of neurons in the ventral respiratory group
  • generation of active contraction of abdominal muscles
164
Q

Neuronal networks much adjust breathing rhythm to accommodate changes in

A
  • metabolic demands
  • varying mechanical conditions
  • non-ventilatory behaviors
  • pulmonary and non-pulmonary diseases
165
Q

Factors that influence Pre-Botzinger and pFGR activity

A
  • neuromodulatory factors/neurotransmitters
  • suprapontine influences that are volitional or emotional
  • sensory inputs that influence rhythm of breathing
166
Q

Once rhythm is generated at level of ventral respiratory group by activity of Pre-Botzinger and pFRG then

A

the excitatory drive moves down neuron pathway so respiratory muscles are activated

167
Q

Inspiratory activity

A
  • Pre-Botzinger complex excite inspiratory neurons in ventral respiratory group
  • excited phrenic and thoracic motor neurons
  • activate the diaphragm and external intercostal muscles
  • activate different cranial motor neurons that control inspiratory activity of the tongue and upper airway muscles
168
Q

Active expiration

A
  • rhythm is generated by pFRG
  • excite expiratory premotor neurons located in ventral respiratory group
  • activate expiratory motor neurons at level of thoracic and lumbar spinal cord
  • activation of internal intercostals and abdominal muscles
169
Q

Peripheral and central chemoreceptors sense changes in levels of

A

PCO2, PO2, and pH
- provide an excitatory drive to centers of brainstem that control respiratory activity

170
Q

What changes in PCO2, PO2 and pH increases ventilation

A
  • hypoxia (low PO2)
  • hypercapnia (high PCO2)
  • acidosis (low pH in blood)
171
Q

2 peripheral chemoreceptors

A
  • carotid and aortic bodies
  • sense changes in arterial PO2 but also sensitive to pH changes
  • sense hypoxia - low arterial PO2
172
Q

Characteristics of carotid bodies

A
  • small and chemosensitive
  • highly vascularized
  • high metabolic rate
173
Q

2 cell populations of carotid bodies

A
  • Type I glomus cells - chemosensitive, drive the response, change in ventilation
  • Type II sustentacular cells - supporting cells
174
Q

Characteristics of glomus cells

A
  • voltage-gated ion channels
  • generate action potentials following depolarization
  • when excited, release neurotransmitters which will excite terminals of glossopharyngeal afferents
  • this nerve will drive excitatory input back to dorsal respiratory group and will excite Pre-Botzinger complex and pFRG to increase respiratory drive and increase ventilation
175
Q

Ventilation is stable over __ - __ mmHg range of arterial PO2

A

60-120 mmHg

176
Q

___ changes on PO2 will have ____ affect in minute ventilation

A

little; little

177
Q

below 60 mmHg, ___ changes of PO2 will have ____ affect in minute ventilation

A

little; large

178
Q

Response to hypoxia (low oxygen) conditions

A

low inspired PO2 –> decrease in alveolar PO2 –> PO2 in arterial blood will decrease –> below 60 mmHg will alter the activity of peripheral chemoreceptors –> increase firing –> activate the pathway that activates the neurons in the medulla –> increase the respiratory rate –> tidal volume –> contractions of respiratory muscles increase –> increase ventilation –> return PO2 to normal level

179
Q

___ changes in PCO2 will have ___ affect in minute ventilation

A

little; large

180
Q

Characteristics of central chemoreceptors

A
  • specialized neurons close contact with blood vessels and cerebrospinal fluid
  • chemosensitive sites are in medullary raphe and hypothalamus
  • sense changes in PCO2
  • CO2 will diffuse from capillary to extracellular space in brain and interact with water to produce H+ (excitatory factor or stimulus)
181
Q

Response of glomus cells to breathing high CO2

A

stimulated by low O2 levels, high concentration of H+ or low pH

182
Q

Response of peripheral chemoreceptors to breathing high CO2

A

increase inspired CO2 –> increase alveolar PCO2 –> increase in glomus cells increase rate of firing and excite the glossopharyngeal nerve –> drive activity in dorsal and ventral respiratory group where PreBotzinger complex and pFRG are located –> increase ventilation

183
Q

Response of central chemoreceptors to breathing high CO2

A

increase inspired CO2 –> increase alveolar PCO2 –> increase arterial PCO2 –> increase brain extracellular fluid PCO2 –> increase brain extracellular fluid hydrogen ion concentration –> hydrogen ions activate central chemoreceptors and increase rate of firing causing an excitatory drive to ventral respiratory group –> increase ventilation

184
Q

Hypercania

A
  • condition where there is too much CO2 in the blood and arterial PCo2 levels are high
  • mediated by dorsal and ventral respiratory groups and central chemorecepetors
185
Q

Response of ____ chemoreceptors to increase production of acid

A

peripheral
- increased contraction of respiratory muscles, increase ventilation, decrease alveolar PCO2, decrease arterial PCO2, return of arterial hydrogen ions towards normal levels
- H+ does not cross blood brain barrier like CO2 does

Physiology 210 (12 decks)

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