Resp System Flashcards
1
Q
Alveoli
A
tiny, thin-walled, capillary-rich sac in the lungs where the exchange of oxygen and carbon dioxide takes place
- about 500 mil in human lung
- about 280 billion capillaries in the lung (70 mL of blood at rest; 200mL during physical activity)
2
Q
Type I alveolar cells
A
- covers most surface of alveolar walls
- flat epithelial cells
- do not divide (susceptible to inhaled or aspirated toxins)
3
Q
Type II alveolar cells
A
- 7% of alveolar surface
- produce surfactant: detergent-like substance made of lipoproteins that reduces the surface tension of alveolar fluid
- progenitor cells (injury to type I = type II can multiply and eventually differentiate into type I)
4
Q
Transfer of O2 and CO2occurs by _________ through the __________ ___________
A
diffusion; resp membrane
5
Q
Diaphragm
A
dome-shaped muscle which flattens during contraction (INS), abdominal contents forced down and forward and rib cage is widened = increase in volume of thorax
6
Q
External intercostal muscles
A
- inspiratory
- contract and pull ribs upward increasing the lateral volume of the thorax
expands lower intercostal - “bucket handle motion” of ribcage
- lateral increase in volume
7
Q
Parasternal intercostal muscles
A
- contract and pull sternum upand forward, increasing anterior-posterior dimension of the rib cage
- “pump handle motion” of the sternum
- anterior increase in volume
8
Q
Abdominal muscles
A
- expiratory
- external & internal obliques, rectus & transverse abdominis
- relaxed at rest
- involved in coughing, vomitting, defecation and posture
9
Q
Internal intercostal muscles
A
- expiratory
- relaxed at rest
- during exercise, internal intercostal muscles pull rib cage down, reducing thoracic volume
10
Q
Scalenes
A
- insp
- elevate upper ribs
Not active during rest; only active during exercise and forced resp to potentiate process of ventilation
11
Q
Sternocleidomastoid
A
- insp
- raise the sternum
Not active during rest; only active during exercise and forced resp to potentiate process of ventilation
12
Q
Pectoralis
A
- insp
- elevates ribs
Not active during rest; only active during exercise and forced resp to potentiate process of ventilation
13
Q
Obstructive sleep apnea
A
reduction in upper airway patency during sleep (snoring, apneas, sleep disturbances)
- anatomical defects
- reduction in muscle tone
increased risk of CV disorders like hypertension; CPAP
14
Q
CPAP
A
continuous positive airway pressure
15
Q
Spirometry
A
pulmonary function test to determine the amount and the rate of inspired and expired air
- records the amount and the rate of air that you breathe in and out over a period of time
16
Q
Tidal volume
A
the volume of air moved in or out of the resp tract (breathed) during each ventilatory cycle (NO EXTRA EFFORT)
17
Q
Inspiratory reserve volume
A
the additional volume ofd air that can be forcibly inhaled following a normal inspiration
- can also be accessed by simply inspiring maximally, to the maximum possible inspiration
18
Q
Expiratory reserve volume
A
the additional volume of air that can be forcibly exhaled following a normal expiration
- can be access simply by expiring maximally to the mac voluntary expiration
19
Q
Residual volume
A
that volume of air remaining in the lungs after a maximal expiration
- cannot be expired no matter how vigorous or long the effort
- cannot be measured with a spirometry test
- RV = FRC - ERV
- *lungs never empty**
20
Q
Vital capacity
A
mac volume of air that can be forcibly exhaled after a maximal inspiration
- VC = TV + IRV + ERV
21
Q
Inspiratory capacity
A
the maximal volume of air that can be forcibly inhaled
- IC = TV + IRV
22
Q
Functional residual capacity
A
the volume of air remaining in the lungs at the end of a normal expiration
- FRC = RV + ERV
23
Q
Total lung capacity
A
the volume of air in the lungs at the end of a maximal inspiration
- TLC = FRC + TV + IRV = VC + RV
24
Q
Volume of air at each breath
A
tidal volume (~0.5 L)
25
Minute (total) ventilation
total amount of air moved into respiratory system per minute
- TV x respiratory frequency (0.5L x 15 bpm = 7.5L/min)
26
Alveolar ventilation
amount of air moved into the alveoli per minute (alv vent < minute vent)
- depend on anatomical dead space (150 mL)
- subtract 150 mL from tidal volume (~0.5L) and multiple bpm
27
FEV1
- forced expiratory volume in 1 sec
| - healthy person can normally blow out most of the air from the lungs within one second
28
FVC
- forced vital capacity
- total amount of air that is blown out in one breath after max inspiration as fast as possible
- TV + IRV + ERV
- similar to vital capacity
29
FEV1/FVC
proportion of the amount of air that is blown out in 1 second
- can be used in asthma patients to see if drug is effective in reducing bronchospasm (beta 2 adrenergic agonist drugs)
30
Obstructive lung disease
- shortness of breath due to difficulty exhaling all the air from the lungs
- due to damage to lungs or narrowing of airways (bronchial constriction), exhaled air comes out more slowly than normal
- at end of a full exhalation, an abnormally high amount of air may still linger in lungs
- exp process is longer
- bronchial asthma, cystic fibrosis, COPD
- FEV1 significantly reduced and FVC is normal/reduced (ration reduced to less than 70% or 0.7)
31
Restrictive lung disease
- cannot fully fill their lungs with air
- lungs restricted from fully expanding
- reduced vital capacity
- most often results from a condition causing stiffness in lungs themselves
- other cases: stiffness of the chest wall, weak muscles, or damaged nerves
- lung fibrosis, neuromuscular diseases (ALS, muscular dystrophy) or scarring of the lung tissue
- reduced vital capacity, FEV1 reduced, FVC reduced, FEV1/FVC almost normal
32
Helium dilution method
- only measures communicating gas or ventilated lung volume
- used to measure functional residual capacity (amount of air that remains in lungs at end of normal exp)
- spirometer connected to a certain specified vol of inert gas (this case is helium)
- Helium not taken up by vascular system; confined in lungs and able to move inside resp system during resp
- we know after equilibria, gas will be diluted so new conctn C2, gas will be dissolved not only in the machine which is V1 but also V2 (corresponds to FRC) or areas in resp system that are available for gas exchange
- V2 = FRC
33
Static properties of the lung
mechanical properties when no air is flowing (necessary to maintain lung and chest wall at a certain volume)
- intrapleural pressure (P ip), transpulmonary pressure (P tp)
- static compliance of the lung
- surface tension of the lung
34
Dynamic properties of the lung
mechanical properties when the lungs are changing volume and air is flowing in and out (necessary to permit airflow)
- alveolar pressure (P alv)
- dynamic lung compliance
- airway and tissue resistance
35
Bulk flow
gas moving from high to low pressure
36
Boyle's Law
for a fixed amount of an ideal gas kept at a fixed temperature, Pand V are inversely proportional (one increases, other decreases)
37
Pleuras
form a thin double-layered envelope
38
Parietal pleura
covers the thoracic wall and superior face of the diaphragm
39
Visceral pleura
covers the external surface of the lung
40
Intrapleural fluid
- reduces friction of lungs against thoracic wall during breathing
- extremely thin
- ~10 mL
41
This determines the lung volume
interaction between lungs and thoracic cage
42
Intrapleural pressure
pressure within the pleural cavity
- fluctuates with breathing but it is ALWAYS subatmospheric (negative) due to opposing directions of the elastic recoil of lungs and thoracic cage
- acts as a relative vacuum
- if PiP equals Palv = lungs collapse
43
Alveolar pressure
pressure of the air inside the alveoli
- when glottis is open and no air flows into or out of he lungs, the pressures in all parts of the respiratory tree, including the alveoli (Palv) are equal to atmospheric pressure (Patm)
- dynamic element, directly involved in producing air flow
44
This expression goversn the gas exchange between the lungd and atmosphere
P alv - P atm
| F = delta P/R
45
Dynamic element, directly involved in producing air flow
alveolar pressure
46
Transpulmonary pressure
the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall
- PTP = PALV - PIP
- static pressure dependent on this
47
Pressure directly controlled by INS muscles
Intrapleural pressure
| - Ptp and Palv
48
Laminar airflow
the subject invests relatively little energy in airflow RESISTANCE; characteristic to the small airways that are distal to terminal bronchioles
49
Transitional airflow
it takes extra energy to produce vortices -> the resistance increases; airflow is transitional throughout most o the bronchial tree
50
Turbulent airflow
effective resistance to airflow is the highest; in the large airways (trachea, larynx, pharynx), where the airway radius is large and linear air velocities may be extremely high
51
For laminar flow (gases/liquids), Poiseuille's law states...
that airway resistance is proportional to the viscosity of the gas (n) and the length of the tube (l), but is inversely proportional to the fourth power of airway radius (r)
52
Lung compliance
measure of the elastic properties of the lungs and is a measure of how easily the lungs can expand
- can be measured in the presence/absence of airflow
- magnitude of the CHANGE in lung volume produced by a given change in the transpulmonary pressure
- slow measured in the pressure-volume curve
- C = delta lung vol over transpulmonary pressure
53
Static compliance
represents lung compliance measured during periods of no gas flow, such as during an inspiratory/expiratory pause
- determined by the P/V slope when measured at FRC (end of expiratory effort)
54
Dynamic compliance
represents pulmonary compliance during periods of gas flow, such as during inspiration (when transpulmonary pressure continuously changes)
- since during airflow, reflects not only lung stiffness but also airway resistance, against which distending forces have to act
- falls when either lung stiffness or airway resistance increases
- is always less than or equal to static lung compliance (due to resistaance)
55
Hysteresis
- defines the difference between the inflation and deflation compliance paths
- exists because a greater pressure difference is required to open a previously closed (or narrowed) airway than to keep an open airway from closing
56
Lung compliance is determined by: (2)
- elastic components of lungs and airway tissue (elastin, collagen)
- surface tension at the air-water interface within the alveoli
57
Emphysema
- floppy lungs as a result of elastin destruction and alveolar wall destruction
- increased compliance with much less elastic recoil - little changes in PTP = large changes in lung volume
- time to fill and empty lungs increased
- consequence = reduction in surface available for gas exchange
58
Pulmonary fibrosis
- collagen deposition in alveolar walls (response to lung injury, silica dust, asbestosis)
- reduction in lung compliance = higher PTP changes are necessary to generate changes in lung volume
- respiratory membrane is thicker
59
Surface tension
a measure of the attracting forces to pull a liquid's surface molecules together at an air-liquid interface
- water molecules at the surface of a liquid-gas interface are attracted strongly to the water molecules within the liquid mass; cohesive force -- v strong bond!!
60
Effect of surface tension is to...
"cause" the surface to maintain as small an area as possible
61
Pressure is greater in smaller or bigger alveolus?
smaller ; Laplace's equation
62
Most important components of pulmonary surfactant are the ...
phospholipids dipalmitoyl-phosphatidylcholine (DPPC), etc.
63
Alveolar stabilization by surfactant
- surfactant reduces surface tension
- thickness of surfactant decreases with increase of SA -> causes T (in wall of alveoli) to increase with increasing alveolar diameter
- Overall effect = t or surface tension is increased in large alveoli and reduced in smaller one
- tends to equalize pressures between alveoli of different sizes
- dynamic properties of surfactant permit the alveolar surface tension to change with inflation and deflation, as the thickness of the surfactant layer varies inversely with SA
64
Surfactant improves __________ and stabilizes ...
compliance; alveolar size
functions:
- reduce the surface tension of alveolar fluid
- improve lung compliance
- stablize alveoli
65
Regional differences in ventilation due to gravity and posture
- ventilation not equal in different areas of lungs
- back = higher lung activity if lying down and vice versa
- upper zone most inflated if upside down
66
Regional differences in intrapleural pressure
- weight of lungs increases pressure near bottom (Pip = less negative) so less pressure pulling it open than regions at top of lung
- since alveoli at bottom are starting more deflated (if Pip is less negative, Ptp will be smaller), they are able to expand more
- bottom regions of lung receive a larger portion of the inspired air
67
Dalton's Law
in a mixture of gases (air), each gas operates independently, this total pressure is the sum of indiv pressures (partial pressures)
68
Fick's Law
the rate of transfer of a gas through a sheet of tissue/unit time (V; L/min) is proportional to the tissue area and the difference in gas partial pressure between the two sides, a diffusion constant, and inversely proportional
69
Diffusion constant
the amount of gas transferred between the alveoli and the blood/unit time (diffusion) is also proportional to the gas solubility (Sol) in fluids or in tissue
70
Henry's Law
the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in which the liquid is in equilibrium
71
Cardiac output
- Q
| - volume of blood pumped by heart per minute
72
Systemic circulation
high pressure system necessary to deliver blood in peripheral tissue (brain) and overcome high resistance system
73
Pulmonary circulation
low pressure system, needs to deliver blood only to lungs and high pressures are risky (lung edema)
74
Ventilation-Perfusion relationship
- important that inspired air delivered to regions of lungs where blood is flowing and vice versa
- ventilation/perfusion (V/Q) ratio is the balance between lung ventilation and lung perfusion
- ratio between the ventilation and the perfusion is one of the major factors affecting the alveolar (and therefore arterial) levels of PO2 and PCO2
- the greater the vent, the more closely alveolar PO2 and PCO2 will approach their respective values of inspired air
- the greater the perfusion, the more closely the composition of local alveolar air will approach that of mixed venous blood
75
Anatomical VD
volume of conducting airways that do not participate in gas exchange
76
Alveolar VD (lack perfusion)
- regions of lung with high V/Q ratios
- regions that are relatively over ventilated (under-perfused) so that a portion of the fresh air reaching these alveoli can not be taken up by the blood
77
Perfused alveoli that are not ventilated
- low V/Q ratio = airway obstruction = shunt
| - portion of the venous blood doesn't get oxygenated and goes back to arterial blood
78
Regional differences in both lung perfusion and lung ventilation
local ventilation-perfusion ratio determines the local alveolar PO2 and PCO2
79
Ventilation-perfusion matching
homeostatic mechanisms exist to limit mismatch; most important is the unique response of pulmonary capillaries to low O2
- pulmonary hypoxic vasoconstriction
80
Oxygen carried in blood in two forms:
- dissolved (2%)
- combined with Hb (98%)
dissolved O2 follows Henry's Law = O2 content is directly proportional to PO2 and solubility
81
Determinants of Hb saturation
- Arterial PO2 = most important!
| - Cooperative binding = results in sigmoidal dissociation curve
82
Dissociation curve is sensitive to:
- cooperative binding
- pH
- P CO2
- Temperature
83
Polycythemia
increase of Hb amount in blood or reduction of blood volume that increases Hb concentration
84
Carbon monoxide poisoning
- shifts Hb dissociation curve to the left (decreases O2 unloading to tissue)
- reduction in O2-Hb binding
- CO has 200x more affinity for hb compared to O2
85
CO2 is carried in blood in three formsL
- dissolved (5%)
- bicarbonate (60-65%)
- carbamino acid compounds (25-30%)
86
Chloride shift
to maintain electrical neutrality and allow for HCO3- to exit the cells through AE (anion exchanger)
- Cl - goes into RBC while HCO3- goes out
* * H+ stays inside RBC = decrease pH)
87
Carbamino compounds
- combination of CO2 with amino group in blood proteins (globins in Hb)
88
Respiratory acidosis
- hypoventilation (CO2 production >> CO2 elimination)
| - not only PCO2 increase but also H+ concentration increases
89
Respiratory alkalosis
- hyperventilation (CO2 production << CO2 elimination)
| - not only PCO2 decrease but also H+ concentration
90
Metabolic acidosis
increase in blood H+ concentration independent from changes in PCO2
91
Metabolic alkalosis
decrease in blood H+ concentration independent from changes in PCO2
92
Neural networks must adjust rhythm o accommodate changes in:
- metabolic demands (as reflected by changes in blood PO2, PCO2, and pH)
- varying mechanical conditions (changing posture)
- non-ventilatory behaviours (speaking, sniffing, eating, etc.)
- pulmonary and non-pulmonary diseases
93
Rhythmic activity also influenced by (2):
sensory and neuromodulatory neurotransmitters inputs originating from different regions within and outside the CNS
94
Peripheral chemoreceptors
- carotid and aortic bodies
- different from aortic and carotid sinuses (baroreceptors)
- sense primarily hypoxia (low arterial PO2) but are also sensitive to pH
95
Carotid bodies
- extremely small
- chemosensitive (type I or glomus cells)
- highly vascularized (40x more than brain)
- high metabolic rate (up to 3-fold greater than that of the brain)
- PO2, PCO2, and pH in the carotid body capillaries is virtually the same as in the systemic arteries
- type II (sustentacular cells) act as support in the CB
- have neuron-like characteristics
96
Primary stimulus for the peripheral chemoreceptors/carotid bodies
decrease in arterial PO2
- > lowering of PO2 = glomus cells increase firing rate
- > glomus cells also sensitive to changes in PCO2 and pH (increase response to hypoxia)
97
When does stimulation of peripheral chemoreceptors occur?
values below 60 mmHg
| ventilation is stable over 60-120 mmHg range
98
How do peripheral chemoreceptors mediate response to hypoxia?
- activate dorsal and ventral resp group neurons in medulla in order to control centrally the activity of the respiratory muscles via
- increasing resp rate
- increasing tidal volume
99
Ventilatory changes with changes in arterial P CO2
Very little changes in PCO2 can provide very large change in minute ventilation
100
Central chemoreceptors
specialized neurons located close to the ventral surface of the medulla (close contract with blood vessels and CSF)
- other chemosensitive sites = medullary raphe and hypothalamus
- responsible for 70% of response to hypercapnia
- again, mediated by effects at the level of dorsal and ventral RG that change ventilation
101
Respiratory response to metabolic acidosis
- H+ stimulates mostly peripheral chemoreceptors because H+ does not cross easily BBB (as CO2 does)
