What does internal respiration refer to?
The intracellular mechanisms which consume O2 and produce CO2
What does external respiration refer to?
Events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body
What are the 4 steps of external respiration?
Gas exchange (alveoli-blood)
Gas exchange (blood-tissues)
Which 3 body systems are involved in external respiration?
The mechanical process by which air is moved between the atmosphere and the alveolar air sacs
Air flows from a region of ___ pressure to ___ pressure
Intra-alveolar pressure must be greater than atmospheric pressure for air to flow into the lungs. True/False?
Intra-alveolar pressure must be less than atmospheric pressure, since air flows from high to low pressure
At constant temp, as the volume of a gas increases, the pressure exerted _____ (Boyle’s Law)
Before inspiration, intra-alveolar pressure = atmospheric pressure. True/False?
Which 2 forces hold the lung and thoracic wall in close opposition?
Intrapleural fluid cohesiveness
Negative intrapleural pressure
Describe intrapleural fluid cohesiveness
Water molecules present in intrapleural fluid are attracted to each other/resist being pulled apart
This causes pleural membranes to stick together
Describe the effect of sub-atmospheric intrapleural pressure
Creates a transmural pressure gradient across the lung and chest wall, causing lungs to expand outwards while the chest squeezes inwards (inspiration)
Intra-alveolar pressure = 760
Intrapleural pressure = 756
What happens across the lung wall?
Lungs expand outwards
Intrapleural pressure = 756
Atmospheric pressure = 760
What happens across the thoracic wall?
Chest squeezes inwards
Contraction of the diaphragm causes the volume of thorax to increase in which direction?
What is the function of external intercostal muscle in inspiration?
Lifts ribs up, pushes out sternum
What is a pneumothorax?
Air in the pleural space
What is the function of surfactant?
Reduces alveolar surface tension
Smaller alveoli have a smaller tendency to collapse. True/False?
More likely to collapse
What secretes surfactant?
Type II alveoli
What cause respiratory distress syndrome in new borns?
Not enough surfactant, leading to high alveolar surface tension
Describe alveolar interdependence
When one alveoli starts to collapse, surrounding alveoli recoil in resistance, pulling the collapsing alveoli open
What are the 2 main accessory muscles of respiration?
What is meant by tidal volume?
Volume of air entering/leaving the lungs in a single breath
What is meant by inspiratory reserve volume?
Volume of air that can be maximally inspired beyond the tidal volume
What is meant by inspiratory capacity?
TV + IRV
What is meant by expiratory reserve volume?
Volume of air that can be maximally expired beyond the tidal volume
What is meant by residual volume?
Volume of air remaining in lungs after maximal expiration
What is meant by functional residual capacity?
Volume of air remaining in lungs following normal expiration
ERV + RV
What is meant by vital capacity?
Volume of air that can be maximally expired following maximal inspiration
TV + IRV + ERV
What is meant by total lung capacity?
Maximum volume of air the lungs can hold
VC + RV
Residual volume can be measured with a spirometer. True/False?
What is meant by forced vital capacity?
Volume of air that can be forcefully maximally expired following maximum inspiration
In obstructive airways disease, FVC is low and FEV1 is low, but the FEV1/FVC ratio stays the same. True/False?
FVC is normal/low, FEV1 is low, FEV1/FVC ratio is reduced
In restrictive airways disease, FVC is ___ and FEV1 is ___, and the FEV1/FVC ratio is ____
Low, low, normal
What is the primary determinant of resistance to airflow?
Radius of the conducting airway
Intrapleural pressure falls during expiration. True/False?
Rises during expiration; falls during inspiration
What is meant by dynamic airway compression?
The rising intrapleural pressure during expiration compresses the alveoli and airway
What is pulmonary compliance?
How easy/difficult it is to stretch the lungs
Low pulmonary compliance means that the lung does not have to work as hard to inflate. True/False?
Decreased compliance means more effort isrequired to inflate the lungs
What is anatomical dead space with regards to airways?
Part of the airways where gas exchange does not occur
Pulmonary Ventilation = volume of air breathed in and out per minute = ?
RR x TV
Alveolar ventilation is greater than pulmonary ventilation. True/False?
It is less than pulmonary ventilation due to dead space
Define alveolar ventilation
Volume of air exchanged between the atmosphere and alveoli per minute
How can pulmonary ventilation be increased?
Increase the depth of breathing
Increase the respiratory rate
Blood flow is faster at the top of the lungs. True/False?
Faster at the bottom
V/Q ratio is better at the top of the lungs. True/False?
Accumulation of CO2 as a result of _____ perfusion leads to _____ airflow (by _____ airflow resistance)
Increased, increased, decreasing
Accumulation of O2 as a result of ____ ventilation leads to pulmonary vaso____
What are the 4 factors which influence the rate of gas exchange across the alveolar membrane?
Partial pressures of O2 and CO2
Diffusion coefficient of O2 and CO2
Surface area of membrane
Thickness of membrane
The partial pressure of O2 is less than the partial pressure of CO2. True/False?
What is the diffusion coefficient of a gas?
The solubility of the gas in membranes
The diffusion coefficient of CO2 is __ times that of O2
The amount of gas that will dissolve in a given volume is proportional to the ________ of the gas at equilibrium within the liquid (Henry’s Law)
If the partial pressure is increased, less gas will dissolve. True/False?
More gas will dissolve
PO2 is normally ___ mm Hg (___ kPa)
100 mm Hg, 13.3 kPa
Most O2 is transported in the blood in the dissolved form. True/False?
Most is bound to haemoglobin
How many haem groups does one haemoglobin molecule contain?
What is the primary determination of haemoglobin O2 saturation?
When the concn of haemoglobin is decreased, what happens to oxygen saturation? Why?
Stays the same
Remaining haemoglobin is still fully saturated as PO2 remains the same, but less haemoglobin means there is less oxygen being carried in total - but saturations are normal!
Binding of one O2 to haemoglobin increases affinity of Hb for O2. True/False?
What is the Bohr Effect?
Increased release of O2 from Hb at tissues (sigmoid shifts to right)
Where is myoglobin mainly present?
Skeletal and cardiac muscle
What shape is the dissociation curve for myoglobin and oxygen?
Presence of myoglobin in the blood indicates what?
What are the 3 methods of CO2 transport in the blood?
As carbamino compounds
Most CO2 is transported in the blood as what?
Which enzyme catalyses formation of bicarbonate?
Carbonic anhydrase in RBCs
Where does CO2 bind on haemoglobin to form carbaminohaemoglobin?
Reduced Hb binds more CO2 than HbO2. True/False?
What is the Haldane Effect?
Removing O2 from Hb increases Hb’s affinity for CO2 and CO2-generated H+
i.e. O2 will be released at tissues; this will increase affinity of Hb for CO2; thus CO2 will be taken up from tissues!
Which part of the brain is the main rhythm generator of breathing?
The breathing rhythm is generated by a group of neurones called the ________
Where is the Pre-Botzinger Complex located?
Upper end of medulla
Inspiration is caused by firing of which neurones?
Dorsal respiratory group neurones
When are ventral respiratory group neurones fired? What do they excite?
In active expiration (hyperventilation) after increased firing of dorsal respiratory group neurones
Excite secondary muscles of respiration
The rhythm generated in the medulla can be modified by neurones in what other part of the brain?
What is the function of the Pneumotaxic Centre in the pons?
Inhibits inspiration; stimulated when dorsal respiratory group neurones fire
What is the function of the Apneustic Centre in the pons?
Prolong inspiration; impulses from here excite the inspiratory area of the medulla
Stretch receptors can influence the respiratory centres in the brain. What do they do and guard against?
Guard against overinflation of lungs
Joint receptors influence respiratory centres in the brain, how?
Moving limbs leads to increased breathing
What is the function of chemoreceptors?
Sense values of gas/chemical tensions
Chemoreceptors which sense tension of O2, CO2 and [H+] in the blood
Where are peripheral chemoreceptors located?
Carotid + aortic bodies
Chemoreceptors which sense the [H+] of the CSF
Where are central chemoreceptors located?
Near the medulla
What separates CSF from blood?
CO2 and [H+] diffuse readily across the blood-brain barrier. True/False?
Only CO2 diffuses readily
Stimulation of peripheral chemoreceptors (by [H+]) causes hypoventilation and CO2 retention. True/False?
Hyperventilation and CO2 elimination