Exam 3 Flashcards
1
Q
what happens to barometric pressure as altitude increases
A
it decreases
2
Q
why is surfactant needed for lungs to inflate
A
b/c the fluid that coats the lungs has a higher surface tension and makes it harder for them to inflate
3
Q
what things can cause a LOW V/Q ratio
A
lung disease, airway obstruction or lung stiffening
ventilation gets reduced
4
Q
what happens to alveoli in low V/Q ratios
A
they are over-perfused and underventilated
getting blood but not enough air
5
Q
what things can cause a HIGH V/Q ratio
A
vascular obstruction
pulmonary hypotension
pulmonary blood flow is reduced
6
Q
what happens to alveoli in high V/Q ratios
A
ventilation is higher than blood flow
7
Q
what things can result in hyperventilation?
A
- hypoxia
- increased temp
- acidosis
8
Q
what things can result in hypoventilation?
A
- CNS depressed by injury or drugs
- injured phrenic nerve
- damaged thorax or resp. muscles
- severe airway obstruction
- lung disease that decreases compliance
9
Q
what happens to PaCO2 in alveolar hypoventilation
A
it is elevated due to insufficient alveolar ventilation
10
Q
what happens to PaCO2 in alveolar hyperventilation
A
it decreases due to an increase in ventilation
11
Q
what factors affect the rate of gas movement between alveolus and blood (VO2)
A
surface area
the thickness of blood air barrier
driving pressure gradient
12
Q
in diseased lungs where there is edema or inflammation, what factors of gas movement are affected
A
thickness of blood-air barrier (thickened)
reduced SA available for lung exchange
13
Q
how does a Right to left vascular shunt result in a lower PaO2?
A
R ventricle blood bypasses the ventilated lung and the deoxygenated blood mixed w/ the oxygenated blood of the left atrium,
dilutes the [O2] in the blood going into systemic circulation = decreased PaO2
14
Q
what are the steps of exhilation
A
- phrenic nerve stops firing
- inspiratory muscles relax = passive recoil of the chest wall and diaphragm
- elasticity of the thorax and lung decreases, alveoli size decreases and Palv increases
- when Palv > Patm, air leaves lungs
15
Q
what are the steps of inhalation
A
- motor neurons fire in phrenic nerve
- stimulates diaphragm to contract
- increases thoracic cavity
- pressure inside pleural cavity becomes more (-) and alveoli expand
- P atm > Palv so air enters lungs
- air moves down pressure gradient from atmosphere to alveoli passively by bulk flow
16
Q
what is functional residual capacity
A
the volume of gas remaining in lungs when the chest wall is relaxed
(‘left over’ air in lung)
17
Q
what is tidal ventilation
A
the movement of air bidirectionally into and out of the lung via the same pathway
18
Q
what are the elastic forces for lung resistance during expiration
A
- elastin fibers in lungs
- surface tension
19
Q
what things cause a left shift in the O2-Hb curve
A
decreased PCO2
increased pH
decreased temp
decreased 2,3 DPG
20
Q
what things cause a right shift in the O2-Hb curve
A
increased PCO2
decreased pH
increased temp
increased 2,3 DPG
hypoxia
high altitude
21
Q
why is the O2-Hb curve sigmoidal?
A
positive co-operativity
22
Q
what form of O2 can exert partial pressure
A
only dissolved O2
23
Q
what is p50
A
the partial pressure at which Hb is 50% saturated
24
Q
what causes an increase in 2,3 DPG
A
hypoxia
25
what are the 3 major types of respiratory surfaces
invaginated - lungs
evaginated - gills
trachea - insect air-filled tubes
26
is ventilation active or passvie
active!
27
what is the importance of the pleural cavity?
pleural cavity = thin, fluid filled space
the fluid it contains reduces the friction, allowing pleurae to slide against each other
fluid also acts to glue lungs to the chest wall
the pressure in the pleural cavity is negative compared to atm pressure, this keeps the lungs slightly expanded
28
slight changes in what are responsible for the movement of air into/out of lungs
Alveolar pressure (Palv)
29
under what pressure conditions does air enter the lung? when does it exit?
enters lungs when Palv < Patm
exits lungs when Palv > Patm
30
Amount of air that can be exhaled after a normal
exhalation
expiratory reserve volume (ERV)
31
Amount of air that can be further inhaled after a
normal inhalation
inspiratory reserve volume (IRV)
32
Air left in the lungs after a forced exhalation
residual volume (RV)
33
Maximum amount of air that can be moved in or
out of the lungs in a single respiratory cycle
vital capacity (VC)
34
Total volume of air in the lungs after a maximal
inspiration
total lung capacity (TLC)
35
is surface tension higher during expiration or inspiration
higher during inspiration (inflation)
36
affect of activation of parasympathetic system on ventialtion
parasympathetic system releases ACh on muscarinic receptors ---> bronchoconstriction
*protective mechanisms that is activated by irritant materials or inflammatory mediators like histamines / cytokines
*activated in heaves and asthma
37
affect of activation of sympathetic system on ventialtion
sympathetic system releases Epinephrine from adrenal medulla, activating B2 adrenergic receptors
---> relaxation of smooth muscle + dilation
38
Some species utilize nitric oxide as
a _________ via a
nonadrenergic noncholinergic
inhibitory nervous system
bronchodilator
39
term for volume of gas contained in conducting airways
anatomical dead space
40
equation for Tidal Volume
VT = VA + VD
41
what is VA (Alveolar ventilation volume)
the amount of tidal volume available for gas exchange
42
what is VD
dead space volume (amount of VT NOT available for gas exchange)
43
what is 'alveolar ventilation'
the amount of 'fresh' air reaching lungs per minute
44
what is minute volume (VE)
the total volume of air moved into and out of the lungs per minute
45
equation for minute volume (VE)
*includes ventilation of dead space)
VE = VT x f
f : respiratory frequency (breaths/min)
46
Functional (alveolar) minute ventilation (dot on V) (VA)
*better than VE b/c excludes ventilation of dead space
dot VA = VA x (breaths/min)
47
alveolar ventilation equation
48
alveolar gas PO2 (PAO2)
100mmHg
49
alveolar gas PCO2 (PACO2)
40mmHg
50
PO2 of cells, interstitial fluid
<40 mmHg
51
PCO2 of cells, interstitial fluid
>46 mmHg
52
Pressure gradient for O2 is 10x that of CO2, yet CO2 diffuses 2x as fast as O2, how?
Diffusivity (D) for CO2 is 20 times that of O2 at any
given partial pressure gradient
CO2 is much more soluble than O2 in water and lipid
membranes
53
how to calculate gas partial pressure (Pgas)
Pgas = barometric pressure x fractional concentration of gas
54
What causes PO2 to drop during inspiration?
air gets saturated w/ water
water reduces the partial pressure of gas in air
55
PIO2 (partial pressure of O2 in HUMIDIFIED air)
subtract H2O vapor pressure, 47 mmHg, from the barometric pressure
56
what is FIO2
fraction of oxygen in inspired air
57
what is PAO2 and how do we estimate it
Partial pressure of O2 in alveoli
estimated using alveolar gas equation
58
what is R, or RQ
respiratory quotient = the ratio of carbon dioxide production to oxygen consumption
R = 0.8
59
what factors contribute to the normal PAO2 - PaO2 gradient (PAO2 > PaO2) alveolar O2 > arterial
– diffusivity of O2 across alveolar membranes
– shunting of blood to non-respiratory areas of the lung
– venous admixture of blood from bronchial and coronary circulation
60
what things could increase the PAO2 - PaO2 gradient?
diseases that cause edema/inflammation, V/Q mismatch, or increased shunts
61
Extra alveolar vessels dilate in response
to ???
expansion of the pleural cavity ---> increased negative pleural pressures ----> increase transmural
pressure
62
what happens to capillary resistance if the lungs expand to max volume
it begins to deform the capillaries making them more
elliptical, increasing resistance
63
why does hypoxia cause vasoconstriction of pulmonary arteries
hypoxia is the result of poorly ventilated alveoli w/ low pO2s.
no point in sending blood to areas that are not receiving oxygen so vasoconstriction redistributes the blood to areas of the lung that are ventilated
64
how could vasoconstriction during hypoxia cause right-sided heart failure?
Resistance increases during vasoconstriction and thus pulmonary arterial pressure increases causing the right ventricle to work harder
65
explain the relationship b/w the thickness of vascular smooth muscle (VSM) in pulmonary arteries and hypoxic vasoconstriction (HV)
VSM is species-dependent (thick in cows and pigs, intermediate in horses, thin in dogs and sheep)
the thickness of VSM layers affects resposde to HV
the thicker the VSM, the stronger the response to HV
66
role of nitric oxide in hypoxia
Some animals like sheep and llama release NO in
response to change in altitude and this acts as a
vasodilator to counteract the constriction due to
hypoxia
67
how can exercise cause an INCREASE in diffusion capacity (DL)?
exercise can cause a 3 fold increase in diffusion capacity by....
surface area (A) increases
* more pulmonary capillaries open to ventilated areas
* deeper breathing stretches alveoli
thickness (L) decreases
* deeper breathing stretches alveoli, thinning membrane
68
what is the primary determinant of the rate of gas exchange?
pressure gradient
(since diffusion capacity is typically unchanged)
69
what things could cause an impaired diffusion capacity (DL)?
* Pulmonary Fibrosis:
– interstitial fibrous tissue increases diffusion distance
* Pneumonia:
– fluid or pus in alveoli increases diffusion distance (L)
* Congestive heart failure:
– edema in lung increases diffusion distance (L)
70
What ultimately limits the amount of O2 that can be taken up by the lungs
cardiac output
----> the maximum rate at which blood can be
delivered to the lungs by the heart
*called the perfusion limitation hypothesis*
71
under what conditions can oxygen uptake be diffusion limited?
if there is insufficient time for equilibration to occur between the blood and the alveolar gas (rare in
healthy animals), and/or if the diffusion capacity (DL) is abnormally low
72
why is it impossible for the V/Q (ventilation:perfusion) ratio to be = 1
due to branching patterns in the respiratory system and gravity.
73
Dissolved oxygen is directly proportional to what
partial pressure of O2 (PO2)
74
The degree of saturation of Hb is proportional to
partial pressure of O2 (PO2)
75
What does a higher P50 mean in regards to Hb affinity for O2
higher P50 = lower affinity of Hb for O2
and a lower P50 = higher affinity of Hb for O2
76
Oxygen carriage directly dependent on...
hemoglobin content
77
erythropoietin stimulates _______ in the _______
red blood cell production (erythropoiesis) in bone marrow
78
what is erythropoietin produced by and what stimulates its synthesis?
produced by interstitial cells in the peritubular capillary bed of the renal cortex
synthesis is stimulated by : hypoxia and androgens
79
how does erythropoietin work
It increases the number of erythropoietin-
sensitive stem cells in the bone marrow that are converted into red blood cell precursors.
80
Factors that lower the affinity of Hb for O2 and promote the unloading of O2 at tissues (Bohr
effect)
- increased temp
- increased CO2
- increased [H+] (decreased pH)
**all can be a result of metabolism
81
what is the effect of increased nitrite levels in the blood
increased nitrite levels can trigger the oxidation of Hb, leading to methemoglobinemia
82
what is methemoglobinemia
oxidized Hb, cannot bind oxygen =functional anemia
83
what is the role of methemoglobin reductase?
converts methemoglobin back to hemoglobin
84
what is the initial response of the respiratory system at high altitude?
increased ventilation to increase tissue PO2
this decreases PCO2 and increases pH
increased 2,3 DPG shifts curve to the Right, enhancing O2 unloading at tissues
85
what is the long-term effect / response of the respiratory system at high altitude?
increased hematocrit which increases O2 carrying capacity of blood
increased capillary density which enhances tissue O2 delivery
86
what is 2,3 DPG a product of
glycolysis
87
what can cause an increase in 2,3 DPG
hypoxia
88
what is the effect of 2,3 DPG on Hb
it binds to Hb, causing a conformational change that reduces its affinity for O2
this shifts the curve to the right
increasing O2 unloading at tissues
89
why does PO2 remain high in carbon monoxide poisoning
b/c tissues are unable to take up O2
90
why are ruminants susceptible to methemoglobinemia?
because the gut flora reduces nitrate to ammonia, with nitrite as an intermediate product.
91
clinical signs of methemoglobinemia?
Rapid, weak heartbeat with subnormal body temperature, muscular tremors, weakness, and ataxia are early signs of toxicosis when methemoglobinemia reaches 30%–40%.
Brown, cyanotic mucous membranes develop rapidly as methemoglobinemia exceeds 50%.
92
what makes carbon monoxide so toxic
it has 240 x greater affinity for
Hb than O2.
-- binds to Hb in same location as O2, reducing ability of Hb to carry O2
-- also increases affinity of Hb for O2
-- shifts dissociation curve to the left & Ihinders O2 unloading at tissues
93
In what two scenarios is CaO2 (arterial oxygen) decreased
in anemia and carbon monoxide poisoning
94
Most CO2 that diffuses into RBC reacts with H2O to
form
carbonic acid
95
what is the Haldane effect
the removal of O2 from Hb at tissue allows more CO2 and H+ to be removed from tissues at any given PO2
96
what are the respiratory control centers in the brainstem
Medullary
- rostral ventromedial neurons (pre-Botzinger)
-dorsal respiratory group
- ventral respiratory group
Pons
- pneumotaxic center
- apneustic center
97
what are the higher centers of resp control
cortical control
limbic system
hypothalamic center
98
what is the role of the rostral ventromedial neurons (pre-Botzinger) in respiration
rhythm generators
99
what is the role of the dorsal respiratory group in respiration? when is it active
inspiration
active during eupnea & innervates the diaphragm via phrenic nerve
100
what is the role of the ventral respiratory group in respiration?
has both inspiratory and expiratory neurons
active during forced expiration (coughing)
101
role of pneumatic center in respiration ?
turns off inspiration at the dorsal respiratory group
102
role of apneustic center in respiration?
prolongs inspiration, shortened expiration
103
role of cortical control in respiration
voluntary control of vocalization, sighs, breath-holding
104
role of lymbic system in respiration
emotionally induced changes in ventilation
105
hypothalamic control of respiration
temperature control
like fever
106
what are the sensors of the respiratory system
central and peripheral
central = chemoreceptors
peripheral = both chemo and mechanoreceptors
107
where are the central and peripheral resp. sensors located
central : ventral surface of medulla
peripheral : carotid and aortic bodies
108
what are the glomus cells related to and what do they respond to
peripheral respiratory sensors
glomus cells respond to hypoxia (likely hypercapnia and low pH too)
109
what do peripheral sensors detect changes in
changes in PaO2 (if drop below 60-70 mmHg)
110
what do central sensors detect changes in
increased H+ in CSF (as a result of CO2 diffusing across BBB)
sensitive to CO2 levels
111
what is the Hering-Breuer reflex
has to do with pulmonary stretch receptors, which respond to stretch (inflation of lungs)
Hering-Breuer reflex inhibits further inspiration
typically only active at large tidal volumes >1
112
mechanoreceptors that increase ventilation w/ limb movement
chest wall and proprioceptive receptors
(muscle spindles, tendon organs, joint receptors)
113
what is the response of irritant receptors?
bronchoconstriction
114
what are J receptors? what causes them to be active?
they stimulate respiration in response to the engorgement of pulmonary capillaries (ex: left heart failure “backs up” pulmonary circulation)
located in alveolar walls near capillaries
115
what is the likely reason for the ventilatory response to exercise?
impulses from the motor cortex (hypothesis)
116
what things depress the activity of macrophages in the respiratory fluid lining
Glucocorticoids, corticosteroids, hypoxia and viral activity
117
Endotherms can respond to changes in temperature by changing their.....
metabolic rate - rate at which they consume O2 and produce CO2
118
what mechanisms do animals use within the thermoneutral zone
pilomotor responses (hair and feathers)
vasomotor responses change the rate of blood flow to skin
postural responses alter the amount of SA exposed to the environment
119
methods of evaporative cooling
sweating
panting
gular fluttering
**all require Energy
