respiratory 21 Flashcards
what forces allow expiration to occur passively at rest?
elasticity( of the lungs) and surface tension( in the lungs)
Elasticity
ability to recover the initial volume after inspiration
based on physical properties
Lungs are distensible
what proteins produce elasticity in the lungs?
elastin and collagen
surface tension
Molecules within a liquid have cohesive forces with all
neighbouring atoms. But, those on the surface (i.e. at a liquid-gas interface) have no neighbouring atoms above, and so exhibit
stronger attractive forces upon their nearest neighbours on the
surface. This enhancement of the intermolecular attractive forces
at the surface is called surface tension.
surface tension force in the lung
In the lung there is ONE liquid-gas interface on the inside. Air inside the alveolus. Surface tension is providing a deflation/collapsing pressure. Net inward collapsing force.
Leplace’s Law: P= 2T/R. P-pressure, T-surface tension, R-radius of alveolus. So bid alveolus would have less collapsing pressure than a small one.
pressure-volume relationship of the Lung
what affect does COPD( chronic obstructive pulmonary disease) have on compliance?
increases compliance. Less pressure is required to generate volume change( inflate the lungs)
cigarette smoke destroys elastin, loss of part of the recoil force. Difficulty expiring the air( deflating the lungs). Lungs are growing.
What effect does fibrosis have on compliance?
Decreased compliance
what are the risk factors for developing fibrosis?
-industrial environments, coal mining. The inflammatory reaction can affect resident fibroblasts in the lungs to produce more collagen.
fibrosis is associated with laying down more of what protein?
Fibrosis is associated with laying down more collagen. More collagen= stiffer lungs. The patient has trouble inflating the lung.
Need to generate much higher intra-pleural pressure to inflate the lungs.
What is the size of the COPD lung?
longer and wider
Flattened diaphragm.
Mid-sternal space reduced
what is another word for COPD?
emphysema
Fibrosis lung shape
Shorter
Mid-sternal space is increased
Fibrotic tissue
what part of the airway has the highest resistance?
trachea
The total cross-sectional area of all bronchioles
Is much larger than that of the trachea.
how much is cross-sectional area increased from the trachea to the alveoli?
500x
how much time is necessary for gas exchange?
3/4 of sec
what is the change in the diameter of the airways during inspiration and expiration?
Inspiration- airways widen, resistance decreases.
Expiration- airways constrict, resistance increases
what allows the airways to expand and constrict?
smooth muscle
do airways have blood supply?
yes
Where is respitatory centre located?
medulla oblongata
Where is respitatory centre located?
medulla oblongata
how does the brain control the air flow?
Within bronchioles- nerve sense fibres( part of the vagus). Stretch sensitive. As the bronchioles inflate on inhalation the mechanoreceptors stretch and fire AP which go into medulla oblongata( respiratory centre). Sensing the inflation state of the lungs. This is important as the brain needs to be triggered to switch between inflation and deflation phases. Stretch receptors trigger the sympathetic nervous system and cause the airways to dilate on inhalation.
what is intrapleural pressure relative to atmospheric?
~5 mmHg below atmospheric. So if atmospheric pressure= 760 mmHg then intrapleural pressure= ~755 mmHg
what is the volume inside the lung during pneumothorax?
minimum volume
What would the pleural pressure be after a pneumothorax?
0 cmH2O. The same as atmospheric pressure
How does surfactant reduce surface tension in the alveoli?
-binds to water molecules at the air-fluid interface lining the alveoli, interfering with the reducing the inter-molecular cohesive between water molecules. This reduces the internal pressure or “collapsing pressure” exerted on the alveoli, making them easier to inflate.
does air flow more/less turbulently towards the base of the lung?
less turbulently . Greater cross-sectional area
what receptors do sympathetic nerves act on in the lungs?
beta-adrenoreceptors
what receptors do parasympathetic nerves act on in the lungs?
muscarinic receptors
what effect do sympathetic nerves have on the smooth muscle in the lungs?
relaxation-> bronchodilation
what effect do parasympathetic nerves have on the smooth muscle in the lungs?
constriction-> bronchoconstriction
what is the action of salbutamol?
beta-adrenoreceptor agonist
smooth muscle relaxation in the bronchioles
how is the signal sent to the brain about respiration?
stretch-activated mechanoreceptors in the bronchioles. ( vagal)
When inhale- stretch and send signals to the brainstem( medulla oblongata) respiratory center.
The brain can then switch off inflation and start exhalation
+ sympathetic activation to dilate the bronchioles
what is the reason for mechanoreceptor feedback to the brain?
-regulate inhalation and exhalation rthym
-increase sympathetic action to bronchodilate during inspiration
(want to get more air into the lungs)
what is the reason for mechanoreceptor feedback to the brain?
-regulate inhalation and exhalation rhythm
-increase sympathetic action to bronchodilate during inspiration
(want to get more air into the lungs)
what is hering-breuer reflex?
a mechanism for respiratory control and protection in animals, enabling volume-dependent regulation.
In human adults, the reflex begins with prolonged inspiration well exceeding eupneic tidal volume. This thoracic expansion subsequently and gradually activates, slowly adapting pulmonary stretch receptors. These receptors relay a signal through the vagus nerve (on a breath-by-breath basis) to “pump” cells” located within the ventrolateral nucleus of the solitary tract
These pump cells receive these vagal inputs and project the information to the medullary post-inspiratory neurons.
These neurons subsequently project inhibitory signals back to the inspiratory neurons along the lateral portion of the respiratory column, thereby terminating inspiration and beginning a prolonged expiration
