Ch. 4 Respiratory Physiology Flashcards by Cassie Baumgarten

Tidal volume

volume inspired and expired with each normal breath

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Inspiratory reserve volume

volume that can be inspired over and above the tidal volume
used during exercise

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Expiratory reserve volume

volume that can be expired after the expiration of a tidal volume

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Residual volume

the volume that remains in the lungs after maximal expiratory
**cannot be measured by spirometry

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Anatomic dead space

volume of the conducting airways
**approximately 150 mls

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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))

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Inspiratory capacity

sum of tidal volume and IRV

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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

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Vital capacity or forced vital capacity

sum of tidal volume, IRV & ERV
**volume that can be forcibly expired after a maximal inspiration

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Total lung capacity

sum of all four lung volumes
-volume of lungs after a maximal inspiration
**cannot be measured by spirometry

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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

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Which respiratory muscles are not used during normal quiet breathing, but during exercise and in respiratory distress?

external intercostal and accessory muscles

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Expiration is normally an active or passive process?

Normally passive
**used during exercise or when airway resistance is increased b/c of disease

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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

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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

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In the absence of what susbstance, the small alveoli have a tendency to collapse?

surfactant

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What is the mechanism of surfactant?

-lines alveoli
-reduces surface tension– by disrupting the intermolecular forces between liquid molecules= INC compliance

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What cells of the lungs produce surfactant?

type II alveolar cells

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What is surfactant primarily made up of?

phospholipid– dipalmitoylphhatidylcholine (DPPC)

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In babies, neonatal respiratory distress syndrome, what occurs due to lack of surfactant?

atelectasis
–decreased V/Q and right to left shunt, hypoxemia

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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

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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

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What is the major site of airway resistance?

medium sized bronchi

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Which response (parasympathetic vs sympathetic) causes constriction of the airways, decrease the radius and increase the resistance to airflow?

Parasympathetic stimulation
**ie asthma

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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)

1. INC in PCO2 or decreases in pH 2. INC temperature 3. 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

1. decreased PCO2, or INC pH 2. DEC temperature 3. 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?

1. Dissolved CO2 2. Carbaminohemoglobin (CO2 bound to hemoglobin) 3. 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

Ch. 4 Respiratory Physiology Flashcards

(81 cards)