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27 Cards in this Set
- Front
- Back
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why do premature babies have breathing problems (resp distress syndrome)?
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-fetuses have no developed mature type II cells to produce surfactant
-less surfactant -> low compliance ->strenuous breathing. -can lead to inability to breathe or lung collapse and then death |
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What is the role of central chemoreceptors?
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Central chemo receptors respond to Pco2 via H+ of brain ECF
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what is the problem with abnormally low compliance?
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the work of breathing is increased
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what is the problem if lung compliance is too high?
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the lungs might fail to hold themselves open and are prone to collapse
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what is surfactant?
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its a detergent-like substance that reduces cohesive forces between water molecules on the alveolar surface
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what is neural generation of rhythmical breathing
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the basic respiratory rhythm is generated by a central pattern generator in the pre-botzinger complex, a region near the medullary respiratory center.
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what is asthma?
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intermittent episodes of strong contraction of airway smooth muscles, increasing airway resistance
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what determines compliance?
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- stretchability of elastic connective tissue in the lung
- surface tension at the air-water interfaces within alveoli |
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what causes the volume change for inspiration?
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the thoracic cage is expanded in response to muscle contraction.
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what causes asthma?
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chronic inflammation of airways and resulant hyperresponsive airway smooth muscle
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what are the two neural clusters within the medullary respiratory center?
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- dorsal respiratory group (DRG) consists mostly of inspiratory neurons
- ventral respiratory group consists of inspiratory and expiratory neurons, both inactive during normal quiet breathing |
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What are the roles of peripheral chemoreceptors?
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located in the aorta and carotid sinuses, the peripheral chemoreceptors respond to Pco2, H+ and Po2 of arterial blood.
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what are the effects of surfactant?
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it reduces surface tension and increases lung compliance
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what are the causal sequences of ventilation events?
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volume of lung is changed -> volume change causes alveolar pressure change -> deltaP drives air flow into and out of the lungs
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what are lungs' compliance?
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it is defined as their stretchiness.
- how much their volume changes per unit pressure - compliance = (deltaV)/(deltaP) |
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How is volume and pressure related?
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- Inversely
- When lung volume increases, pressure decreases |
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how is ventilation normally primarily controlled?
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-negative feedback controllers sensing Pco2
-small changes in the co2 content of the blood quickly trigger changes in ventilation rate |
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besides from sensing PCo2 what other negative controllers regulate ventilation?
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negative controllers of PO2 and H+
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does feedforward control help control ventilation?
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yes
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how is air flow driven between the atmosphere and alveoli?
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flow is driven by pressure differences
- F= (deltaP)/R |
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how does the volume change for expiration occur?
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the thoracic cage is tightened, in a resting person, simply by muscle relaxation
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how does hypoxia increase [DPG]?
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It increases the rate of glycolysis
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how does acidity of the blood affect ventilation?
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increases in the acidity of blood cause increased ventilation even if CO2 levels are abnormally low
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how do peripheral chemoreceptors sensing decreased O2 increase ventilation?
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they inform the ventilation control center in the medulla which increases rate of ventilation
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How do changes in alveolar pressure occur?
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They are caused by changes in lung dimensions
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describe how passive expiration at rest occurs
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elastic recoil
- nerves to diaphragm and inspiratory intercostal muscles relax - diaphragm and chest wall are no longer pulled outward by muscle contractions : they recoil inward toward their resting dimensions - as the lungs become smaller, their alveoli becomes compressed: alveolar pressure exceeds atmospheric pressure and air flows out |
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At rest, are central or peripheral chemosensors primarily used to sense Pcos to control ventilation?
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central
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