Ch. 4 Respiratory Physiology Flashcards
Tidal volume
volume inspired and expired with each normal breath
Inspiratory reserve volume
volume that can be inspired over and above the tidal volume
used during exercise
Expiratory reserve volume
volume that can be expired after the expiration of a tidal volume
Residual volume
the volume that remains in the lungs after maximal expiratory
**cannot be measured by spirometry
Anatomic dead space
volume of the conducting airways
**approximately 150 mls
Physiologic dead space
volume of the lungs that does not participate in gas exchange
**approx equal to the anatomic dead space in normal lungs
**is a functional measurement with equation( VD= VT X ((PACO2- PECO2)/PACO2))
Inspiratory capacity
sum of tidal volume and IRV
Functional residual capacity (FRC)
sum of ERV (exp reserve vol) and RV (residual vol)
**volume remaining in the lungs after a tidal volume is expired
**cannot be measured by spirometry
Vital capacity or forced vital capacity
sum of tidal volume, IRV & ERV
**volume that can be forcibly expired after a maximal inspiration
Total lung capacity
sum of all four lung volumes
-volume of lungs after a maximal inspiration
**cannot be measured by spirometry
Forced expiratory volume
volume of air that can be expired in teh first second of a forced maximal expiration
**normal 80% of the forced vital capacity
Which respiratory muscles are not used during normal quiet breathing, but during exercise and in respiratory distress?
external intercostal and accessory muscles
Expiration is normally an active or passive process?
Normally passive
**used during exercise or when airway resistance is increased b/c of disease
Which law describes surface tension of the alveoli?
Laplace law:
P= 2T/r
p=collapsing pressure on alveolus (or pressure required to keep alveolus open)
T= surface tension
r=radius of the alveolus
Which alveoli have high/low collapsing pressures and are difficult/easy to keep open?
large alveoli– low collapsing pressure & easy to keep open
Small alveoli– high collapsing pressure & hard to keep open
In the absence of what susbstance, the small alveoli have a tendency to collapse?
surfactant
What is the mechanism of surfactant?
-lines alveoli
-reduces surface tension– by disrupting the intermolecular forces between liquid molecules= INC compliance
What cells of the lungs produce surfactant?
type II alveolar cells
What is surfactant primarily made up of?
phospholipid– dipalmitoylphhatidylcholine (DPPC)
In babies, neonatal respiratory distress syndrome, what occurs due to lack of surfactant?
atelectasis
–decreased V/Q and right to left shunt, hypoxemia
Airflow in the lungs is driven by what?
the pressure difference between the mouth and the alveoli
**proportional to pressure difference & inversely proportional to airway resistance
Q= Change P/R
Q=airflow
Change P= pressure gradient
R= airway resistance
How is resistance to the airway described?
Poiseuille Law
R= (8nL)/ pieR^4)
R= resistance
n= viscosity of the inspired gas
l=length of the airway
r= radius of teh airway
What is the major site of airway resistance?
medium sized bronchi
Which response (parasympathetic vs sympathetic) causes constriction of the airways, decrease the radius and increase the resistance to airflow?
Parasympathetic stimulation
**ie asthma
Which response (parasympathetic vs sympathetic) causes dilation of the airways, increase in the radius and decrease in the resistance to air flow?
sympathetic stimulation
**through beta 2 receptors
Describe pressures and airflow: at rest (before inspiration begins)
-alveolar pressure equals atmospheric pressure
-intrapleural pressure is negative
-lung volume is the FRC
Describe pressures and airflow: during inspiration
-inspiratory muscles contract and cause the volume of the thorax to increase (pressure gradient allows air to flow into the lungs)
-intrapleural pressure becomes more negative
-lung volume increases by one VT
Describe pressures and airflow:
during expiratoin
-alveolar pressure becomes greater than atmospheric pressure (air flows out of lungs)
-intrapleural pressure returns to its resting value during a normal (passive) expiration
-lung volume returns to FRC
What percentage of systemic cardiac output bypasses pulmonary circulation?
**admixture of venous oxygenated and arterial blood making the PO2 of arterial blood slightly lower than alveolar air
2% of systemic cardiac output
physiologic shunt
Which form of iron binds O2?
ferrous state (Fe2+)
Each subunit of hemoglobin contains an iron-containing porphyrin?
a heme moiety
How is the movement of O2 from mother to fetus facilitated?
B/c fetal hemoglobin (alpha2gamma2) has a higher affinity for O2 than adult hemoglobin= left shift
Which form of iron is in methemoglobin, thus no binding of O2 occurs?
Fe 3+ state
What causes shifts in the hemoglobin-O2 dissociation curve: TO THE RIGHT?
**meaning affinity of hemoglobin for O2 is decreased (dec O2 content of blood)
- INC in PCO2 or decreases in pH
- INC temperature
- INC 2,3-DPG
What is the adaptation to chronic hypoxemia (such as living at a high altitude)?
increases synthesis of 2,3 DPG, which binds to hemoglobin and facilitates unloading of O2 in the tissues
What causes shifts in the hemoglobin-O2 dissociation curve: TO THE LEFT?
**meaning affinity of hemoglobin for O2 is increased
- decreased PCO2, or INC pH
- DEC temperature
- decreased 2,3 DPG
Carbon monoxide poisoning causes what shift in the hemoglobin-O2 dissociation curve?
shift of the curve to the left
–> CO competes for O2 binding sites on hemoglobin, decreasing O2 content of blood
What are causes of hypoxemia
decreased PAO2
Diffusion defect
V/Q defects
right to left shunts
define hypoxemia
decrease in arterial PO2
define hypoxia
decreased O2 delivery to the tissues
How does cyanide poisoning cause hypoxia?
decrease O2 utilization by tissues
What growth factor is synthesized in the kidneys in response to hypoxia?
erythropoietin (EPO)
**promotes development of mature RBCs
What are the 3 forms of CO2 in blood?
- Dissolved CO2
- Carbaminohemoglobin (CO2 bound to hemoglobin)
- HCO3-
What is the major form of CO2 in blood?
HCO3-
**90%
The reaction of CO2 combining with H20 to form HxCO3 is catalyxed by what enzyme?
carbonic anhydrase
What dose H2CO3 dissociate into on RBCs
H and HCO3
Explain the chloride shift that occurs on RBCs
HCO3- leaves RBCS in echange for CL
– then trasnported to teh lungs in the plasma
What is the major form in which CO2 is transported to the lungs?
HCO3-
What buffers H inside RBCs?
deoxyhemoglobin
IN the lungs, how is CO2 transported from RBCs?
HCO3 enters the RBCS in exchange for Cl-
–HCO3 recombines with H to form H2CO3– decomposes into CO2 and H20
—Then CO2 expired
in which zone of the lungs is pulmonary blood flow its lowest?
Zone 1 (apex)
alveolar pressure > arterial pressure> venous pressure
in which zone of the lungs is blood flow the highest?
Zone 3 (base)
arterial pressure> venous pressure> alveolar pressure
What is the result of alveolar hypoxia on pulmonary blood flow?
Causes vasoconstriction
**opposite of other organs where hypoxia causes vasodilation
–vasoconstriction redirects blood flow away from poorly ventilated, hypoxic regions of the lung and toward well-ventilated parts of lung
What is an example of a right to left shunt?
tetraology of fallot
– decrease ina rterial PO2 because of admixture of venous blood with arterial blood
What is an example of a left to right shunt?
**patent ductus arteriosus
**do not result in a dec in arterial PO2
What does V/Q ratio stand for?
V= alveolar ventilation
to
Q= pulmonary blood flow
If breathing rate, tidal volume and cardiac output are normal, what is the normal V/Q ratio?
0.8
–arterial PO2 100 mmHg
–arterial PCO2 of 40 mmHg
In what areas of the lung is ventilation at its lowest and highest?
lowest– apex
highest– base
Where is the V/Q ratio highest?
at the apex of the lung (gas exchange is most efficient)
**lowest at the base of the lung
In what part of the lung is gas exchange most efficient?
at the apex
** b/c PO2 is at its highest and PCO2 is at its lowest
If the airways are completely blocked and ventilation is zero, what is the V/Q?
zero
**right to left shunt, see an increase in A-a gradient
What is the V/Q , in the case of a pulmonary embolism?
V/Q= infinite
– called dead space
What occurs to PO2 and PCO2 when the airways are blocked and ventilation is zero?
PO2 and PCO2 of pulmonary capillary blood (therefore of systemic arterial blood) will approach their values in mixed venous blood
What occurs to PO2 and PCO2 when there is a pulmonary embolism?
no gas exchange in the lung tha tis ventilation but not perfused
PO2 and PCO2 of alveolar gas will approach their values in inspired air
Sensory information is coordinated in what part of the CNS?
brainstem
Output from the dorsal respiratory group travel sin what nerve?
phrenic nerve
– travels ot the diaphgram
Input to the dorsal respiratory group comes from what nerves?
vagus: info from peripheral chemoreceptors and mechanoreceptors in the lung
glossopharyngeal nerve: relays info from peripheral chemoreceptors
The apneustic center located in the lower pons, is responsible for?
stimulates inspiration– produces deep and prolonged inspiratory gas (apneusis)
The pneumotaxic center located in the upper pons, is responsible for?
inhibits inspiration– regulates inspiratory volume and respiratory rate
What part of the brain is responsible for voluntary control of breathing?
cerebral cortex
What is the effect of increases in PCO2 and H on central chemoreceptors in the medulla?
stimulate breathing
**hyperventilation
What is the effect of decreases in PCO2 and H on central chemoreceptors in the medulla?
inhibit breathing
**hypoventilation
Central chemoreceptors in the medulla are sensitive to
pH of the CSF
What form of CO2 acts directly on central chemoreceptors in the medulla to effect breathing?
H
**In CSF, CO2 combines with H2O to produce H and HCO3-
Where are peripheral chemoreceptors located for CO2, H and O2 located?
Carotid and aortic bodies
At what level of PO2, are the peripheral chemoreceptors stimulated to effect respiration?
PO2 <60 mmHg
Where are J (juxtacapillary) receptors responsible for and their location?
location: alveolar walls, close to the capillaries
engorgement of pulmonary capillaries, such that may occur with LCHF, stimulates J receptors, causing rapid, shallow breathing
list substances that are biologically activated by the lung?
angiotensin I is converted to the vasocconstrictor, angiotensin II via ACE
List substances that are biologically inactivated by the lung
bradykinin
serotonin
PGE1, E2, and F2alpha
norepinephrine (partially)
What are substances that are metabolized and released by the lungs?
arachidonic acid metabolites– the luekotrienes and prostaglandins
What are substances that are secreted by the lungs?
immunoglobulins– particularly IgA, in bronchial mucus
