3: Physiology I Flashcards
Which gas do cells require to produce energy and function?
Oxygen (O2)
Which gas, produced by cellular reactions, must be continuously removed from our bodies?
Carbon dioxide (CO2)
What is internal respiration?
The intracellular mechanisms which consume O2 and produce CO2
What is external respiration?
The sequence of events involved in the exchange of O2 and CO2 between your cells and the external environment
What is ventilation?
The mechanical process of moving air between the atmosphere and the alveolar sacs
What is Boyle’s Law?
As the volume of a gas increases, the pressure exerted by the gas decreases
i.e a gas’s volume and the pressure exterted by it are inversely proportional
Air flows from a region of ___ pressure to a region of ___ pressure.
high ⇒ low
During inspiration, intra-alveolar pressure is ___ than atmospheric pressure.
less
During inspiration, the thorax and lungs expand as a result of the ___ of inspiratory muscles.
contraction
What minor force causes the pleural membranes to stick together during inspiration?
Intrapleural fluid cohesiveness
The thorax, pleura and lungs stick together because the transmural pressure gradient across the lung wall is ___.
negative
i.e the lungs are pushed AGAINST everything superficial to them
The fact that intra-alveolar pressure is ___ with atmospheric pressure means that the intrapleural pressure is (higher/lower), allowing the lungs to expand with the chest wall during inspiration.
equalized
lower
Which major inspiratory muscle increases the vertical volume of the thorax when it contracts?
Diaphragm
The contraction of the diaphragm increases the ___ volume of the thorax.
vertical
Which nerves control the contraction of the diaphragm during inspiration?
Which spinal nerves innervate the diaphragm?
Phrenic nerves
C3, C4, C5 (C345 keep the diaphragm alive)
The contraction of which muscles lift the ribs and move out the sternum?
External intercostal muscles
Inspiration is an (active / passive) process.
active
The increase in the size of the lungs during inspiration causes a ___ in intra-alveolar pressure.
By which law does this occur?
decrease
Boyle’s Law
Expiration is an (active / passive) process.
passive
Why do the thorax and lungs recoil to their preinspiratory size?
Relaxation of inspiratory muscles
Elastic recoil
Recoil of the lungs causes the intra-alveolar pressure to ___.
By which law does this occur?
rise
Boyle’s Law
In expiration, air leaves the lungs ___ the pressure gradient until intra-alveolar pressure becomes ___ to the atmospheric pressure.
down
equal
Contraction of the diaphragm, during inspiration, causes it to move (up / down).
down
During expiration, the relaxation of the diaphragm causes it to move (up / down).
up
What is a pneumothorax?
Air in the pleural space
Pneumothorax ___ the transmural pressure gradient.
abolishes
The alveolar air spaces and the pleural space become continuous, so there’s no force pushing the lungs outwards against the pleura and thorax
Connective tissue found in the lungs is ___ and allows it to bounce back into shape during expiration.
elastic
Which force resists the stretching of alveoli?
Alveolar surface tension
If the alveoli were lined with water alone, the surface tension would be too ___ and the alveoli would ___.
high
collapse
According to LaPlace’s Law, smaller alveoli have a ___ tendency to collapse.
higher
What is pulmonary surfactant?
Fluid consisting of lipids and proteins which prevent the alveoli from collapsing
Produced by Type II pneumocytes
Which type of alveoli secrete pulmonary surfactant?
Type II alveoli
Pulmonary surfactant ___ alveolar surface tension.
decreases
Pulmonary surfactant tends to have a greater reductive effect on the alveolar surface tension of (larger / smaller) alveoli.
smaller
by Law of LaPlace, smaller alveoli are more likely to collapse, so surfactant is more effective for them
Why can premature newborns develop respiratory distress syndrome?
Premature newborns haven’t produced enough pulmonary surfactant to oppose alveolar surface tension
So their alveoli are more likely to collapse, reducing ventilation and causing respiratory distress
If an alveolus starts to collapse, the surrounding alveoli stretch and recoil to open it - what is this called?
Alveolar interdependence
What is alveolar interdependence?
When an alveolus collapses, it’s stretched and reopened by elastic fibres from surrounding alveoli
What are three forces keeping alveoli open?
Intra-alveolar pressure (transmural pressure gradient)
Pulmonary surfactant opposing AST
Alveolar interdependence
What are two forces which promote alveolar collapse?
ALVEOLAR SURFACE TENSION - resisted by pulmonary surfactant
ELASTIC RECOIL - elasticity of the connective tissue which is seen in expiration
Arrange the following forces into forces keeping alveoli open and forces promoting alveolar collapse:
Alveolar surface tension
Alveolar interdependence
Transmural pressure gradient
Pulmonary surfactant
Elasticity of pulmonary connective tissue
Open:
Transmural pressure gradient
Pulmonary surfactant
Alveolar interdependence
Collapse:
Elasticity of pulmonary connective tissue
Alveolar surface tension
