Respiration - Lecture 7 Flashcards
What can the respiratory system be regarded as?
a pump with elastic, flow-resistive and inertial properties
What happens to the FRC and Ppl of the lungs at rest?
they are negative due to the opposite forces acting on the lungs and chest wall
What happens to the diaphragm and chest wall during inspiration?
the diaphragm contracts and the chest wall is pulled open
What happens to the Ppl during inspiration?
it becomes more negative
What is the formula for flow of breath?
F = (Palv - Patm)/Resistance
The resting position of the lungs is below…
RV
As the lungs are pulled further away from their resting position, what happens to Ppl?
it becomes even more sub atmospheric
As the volume of the lungs is ____, gas in the lungs is ____, Palv drops _____ atmospheric pressure.
increased, decompressed, below
What generates air flow to the lungs during inspiration?
the created negative pressure gradient between the alveoli and atmosphere
What happens to the pressure gradient and the air flow as inspiration proceeds?
they gradually decrease
Why does air flow stop at the end of inspiration?
because Palv is equal to Patm (no pressure gradient)
During expiration, the diaphragm _____, elastic recoil of the respiratory system ____ the gas in the lungs, and Palv ____.
relaxes, compresses, increases
What happens to the positive pressure gradient between the atmosphere and the lungs during expiration?
it causes air from the lungs to be pushed out to the atmosphere
What happens to Ppl as lung volume decreases during expiration?
it slowly returns to its resting level
What is the air flow, Palv and Ppl at the end of expiration?
air flow = 0, Palv = 0, Ppl = -5
What does the time course of changes in pleural pressure during inspiration and expiration depend on?
contraction of the diaphragm and airway resistance
What must occur in order to have gas flow through the airways?
the pressure at the airway opening must be different from that in the alveoli
What is the formula for the resistance of the airways to gas flow?
Raw = (Palv-Pao)/Flow
A ___ diameter airway can carry a ___ flow for a given pressure difference.
large, large
What is airway resistance related to?
airway caliber
What happens to airway resistance during asthma?
it is high making breathing difficult
When a subject inspires to TLC and exhales to RV, during expiration, flow ___ very rapidly to a ___ value and then ___ over the rest of expiration.
rises, high, declines
Why is the descending portion of the flow-volume curve independent of effort?
because of the compression of the airways by intrathoracic pressure
What are the values of airway pressure and intrapleural pressure before inspiration?
airway pressure: 0
intra pleural pressure: -5
What happens to the airway pressure and intrapleural pressure during inspiration?
airway pressure and intrapleural pressures fall
What are the values of airway pressure and airway transmural pressure at the end of inspiration?
airway pressure: 0
airway transmural pressure: 8
What happens to the alveolar pressure and intrapleural pressure during forced expiration?
they increase
Why is there a positive pressure tending to close the airways during forced expiration?
because of the pressure drop along the airways as flow beings
Why does the positive pressure decrease when moving out of the lungs during forced expiration?
because the air is going down over airway resistance (friction)
What kind of recoil is found in restrictive diseases like pulmonary fibrosis?
more recoil (stiff)
What happens to the maximum flow rate and maximum volume exhaled in restrictive diseases?
they are reduced
What happens to the flow rate in obstructive diseases?
it is very low
What kind of recoil is found in obstructive diseases like emphysema?
no recoil
What are the 7 steps of events during inspiration?
Diaphragm and intercostal muscles contract
↓
Thoracic cage expands
↓
Intrapleural pressure becomes more negative (subatmospheric)
↓
Transpulmonary pressure increases
↓
Lungs expands
↓
Alveolar pressure becomes subatmospheric
↓
Air flows into alveoli
What are the 8 steps of events during expiration?
Diaphragm and external intercostal muscles stop contracting
↓
Chest wall moves inwards
↓
Intrapleural pressure goes back towards preinspiratory value
↓
Transpulmonary pressure goes back towards preinspiratory value
↓
Lung recoils towards preinspiratory volume
↓
Air in lungs is compressed
↓
Alveolar pressure becomes greater than atmospheric pressure
↓
Air flows out of the lungs
What increases proportionally when exercise starts?
tidal volume and breathing frequency
What happens to tidal volume?
it plateaus
What happens to ventilatory rates during hard exercise?
they become high due to incremental increases in frequency
Because of the increased breathing frequency, inspiratory and expiratory times ___ during progressive exercise but expiratory times ___ relatively more than inspiratory time.
decrease, fall
Which flow rate increases more?
peak expiratory flow rate
In both untrained and trained subjects, what increases linearly with metabolic rate?
minute ventilation
How much does minute ventilation increase in both trained and untrained subjects?
50 to 60% of VO2 max
Minute ventilation ___ at a rate disproportionately ___ than the change in VO2.
increases, greater
An effect of endurance training is to ___ the ventilatory inflection point.
delay
How much can resting values of minute ventilation increase during exercise in a fit individual?
35 folds
How much can resting values of cardiac output increase during exercise in a fit individual?
5-6 folds
Which increases more during exercise; minute ventilation or perfusion?
minute ventilation
What is one of the reasons why ventilation is not believed to limit aerobic performance?
because there in an increase in Ve/Q
What are the values of minute ventilation and perfusion in less fit individuals?
less than fit ones but the ratio will increase to a similar extent
What is the alveolar surface area?
50 m^2
What is the average blood volume?
5 L
What percentage of blood volume is in the pulmonary system at any one time during maximal exercise?
4%
What kind of response is there in the medullary ECF during exercise?
an alkaloid (increases pH) response
What decreases the ventilatory response during exercise?
an increase in pH
What receptors are mainly sensitive to changes in PO2, but are stimulated by increased PCO2 and decreased pH?
peripheral chemoreceptors
What remains constant during exercise?
PaO2
What decreases during exercise?
PaCO2 and arterial pH
What increases the sensitivity of the peripheral chemoreceptors to CO2 and H+ during exercise?
the fluctuations in PaO2
What do the peripheral mechanoreceptors do to minute ventilation during exercise?
it increases it slightly
What is asthma?
chronic inflammatory disease of the airways
What are the symptoms of asthma?
airway obstruction, enhances airway responsiveness to contractile agonists and/or allergens
What is emphysema?
the enlargement of the air spaces due to the destruction of the walls of the alveoli
What happens to airways in people with emphysema?
they collapse because of the loss of radial traction
What happens to the lungs during emphysema?
they self-destruct, attacked by proteolytic enzymes secreted by leukocytes in response to factors
What is fibrosis?
progressive distortion of the alveolar architecture with inflammation and accumulation of fibrotic tissue
