Physiology 1 - Forces of Respiration Flashcards
Is inspiration active or passive?
Inspiration is active
Which three factors keep alveoli open?
Transmural pressure gradient
Pulmonary surfactants
Alveolar interdependence
Which 2 forces allow lungs to adhere to the chest?
Transmural pressure gradient
Intrapleural cohesion
State the mmHg for Atmospheric Pressure, Alveolar Pressure and Intrapleural pressure
Atmospheric Pressure - 760 mmHg
Alveolar Pressure - 760 mmHg
Intrapleural Pressure - 756 mmHg
During inspiration, which two muscles help most?
Diaphragm - contracts to become flat
External Intercostal Muscles - Lifts ribs upwards and outwards
How does a pneumothorax abolish transmural pressure gradient? What is the result?
Pneumothorax allows air entry into the pleural space and raises pleural (intrathoracic) pressure gradient.
The lung collapses.
What are symptoms of pneumothorax?
shortness of breath
chest pain
what are the physical signs of pneumothorax?
hyperressonant percussion note
decreased/absent breath sounds
Which law states that at constant temperature the pressure exerted by a gas is inverse to the volume of gas?
i.e. when volume of gas increases the pressure exerted by gas decreases
Boyle’s Law
Why is Boyle’s law important to respiration?
For air to flow down its pressure gradient, intra-alveolar pressure should become less than atmospheric pressure.
This happens during inspiration when lungs expand.
Also needed for expiration
Which 2 factors cause lungs to recoil during passive expiration?
Elastic connective tissues
Alveolar surface tension
What reduces alveolar surface tension?
Surfactants
What produces surfactants?
Type 2 alveoli
Name the two major inspiratory muscles
Diaphragm
External intercostal muscles
Name the 3 accessory muscles of inspiration used during forceful inspiration?
Sternocleidomastoid
Scalenus
Pectoral
Name 2 muscles of active expiration?
Abdominal muscles
Internal intercostal muscles
Volume of air entering or leaving lungs during a single breath?
0.5L
Tidal Volume (TV)
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
3.0L
Inspiratory reserve volume (IRV)
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
1.0L
Expiratory reserve volume (ERV)
Minimum volume of air remaining in the lungs even after a maximal expiration
(1.2L)
Residual volume (RV)
Maximum volume of air that can be inspired at the end of a normal quiet expiration
(3.5L)
Inspiratory Capacity (IC)
IC = Inspiratory Reserve Volume + Tidal Volume
Volume of air in lungs at end of normal passive expiration (2.2L)
Functional Residual Capacity (FRC)
FRC = Expiratory Reserve Volume + Residual Volume
Maximum volume of air that can be moved out during a single breath following a maximal inspiration (4.5L)
Vital Capacity (VC)
VC = Inspired Reserve Volume + Tidal Volume + Expired Reserve Volume
Total volume of air the lungs can hold (5.7L)
Total Lung Capacity (TLC)
TLC = Vital Capacity + Reserve Volume.
Which three lung volumes and two lung capacities can spirometry measure?
Tidal Volume
Inspiratory & Expiratory Reserve Volume
Inspiratory Capacity
Vital Capacity
What is the normal Fev1/FVC ratio?
> 75%
Maximum volume that can be forcibly expelled from the lungs following a maximum inspiration
Forced vital capacity (FVC)
Volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination
Forced expiratory volume in one second (FEV1)
In diagnosing restrictive vs obstructive diseases, which measurement differs and which stays the same?
FVC differs
FEV1 same
A peak flow meter is used for obstructive or restrictive lung disease?
obstructive lung disease (e.g. asthma/COPD)
Which nerve innervates the major inspiratory muscles? Name its levels.
Phrenic nerve
C3, 4, 5
