Biomechanics - Respiration Flashcards
What is necessary for respiration to occur?
O2 must be obtained form environment and CO2 removed from body back into it
What is the cellular respiration equation?
C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP
What kind of sources can O2 be extracted from?
water or air
How much air is in water and the atmosphere?
Air = 21% Water = 3-5%
How does respiration occur in worms?
O2 and CO2 diffuse directly between the blood vessels just underneath their skin
For terrestrial animals such as humans, what main organ do we have that allows us to exchange gases?
Lungs
What structure does O2 and CO2 go through to get into our lungs?
Airways
What are the three phases of gas exchange in an animal which has lungs?
1 - Breathing
2 - Transport of gases by circulatory system
3 - Diffusion of gases from blood to cells
What is the order of air flow during inhalation through the different structures of the lungs?
Larynx, trachea, bronchi, bronchioles then alveoli
What is a key feature of alveoli that allows for efficient gas exchange?
High SA:V ratio (FYI there are ~500million alveoli which have a radius of ~125μm and is only one cell thick)
What is the technical term for breathing?
Ventilation
What does ventilation refer to?
The moment of air into and out of the lungs
What is the process of air entering our lungs called? Why does this occur?
- Inhalation
- alveolar pressure decreases below atmospheric pressure
What is the pressure of air leaving our lungs called? Why does this occur?
- Exhalation
- alveolar pressure increases above atmospheric pressure
What is the physical mechanism of ventilation?
- Inhalation: rib cages expand (as rib muscles contract) and diaphragm contracts (moves down)
- Exhalation: rib cage gets smaller (rib muscles relax) and diaphragm relaxes (moves up)
What does a pressure volume charge for the lungs describe?
The change in pressure in the lungs as there is a change in volume
How is the work done by the lungs calculated?
The area between the curves
How does a pressure volume chart differ between one for the lungs and heart?
For lung PV chart the pressure is on the x-axis and volume and y-axis, for heart it is the other way around (e.g. volume on y-axis and pressure on x-axis)
What is the slope of the PV lung diagram called?
Compliance
What is compliance?
A measure of show much the lung volume changes for a given change in pressure
What is the equation for compliance?
∆V/∆P
How does compliance change as volume increases?
Compliance decrease as lung volume increases
What are the three factors that work is required to overcome while breathing?
1 - over come surface tension
2 - expand elastic lung tissue
3 - overcome air resistance as it flows through airways
Where is surface tension found in the lungs?
Where the moist inner surface of alveoli is in contact with air
How does the surface tension in the lungs make it harder to expand the lungs?
Surface tension force resists the expansion of alveoli during breathing
How do lungs reduce the surface tensions of alveoli? How does this aid breathing?
Produce surfactant (is similar to soap) which lowers the surface tensions reducing the work required to expand the alveoli
How does a lack of surfactant impact breathing?
For the same pressure in the lungs it fills up with less air reducing the breathing capacity of the individual
What are the elastic properties of lung tissue determined by?
Collage and elastin
How does the internal structure of the lung fibres change during low and high pressure?
- When pressure is low the fibres are crimped so the lungs are flexible
- When pressure is high the fibres are extended so the lungs are stiff
What happens if the lungs are expanded further than normal full inhalation?
Strain hardening
What are the affects of smoking?
Destroys the elastic tissue of lungs creating large gaps preventing lungs from recoiling/relaxing limiting the amount of air that can be exhaled, known as emphysema
What does resistance in the air ways depend on?
speed of air flow, viscosity of air, air ways radius and airway length
What is the most important factor in airway resistance? How is this mathematically represented? What is this called?
Airway radius as R ∝ 1/r^4 (therefore a small change in r causes a large change in R) represented by Poiseuille’s law
What part of the brain controls the involuntary breathing?
Medula oblongata
What is breathing influenced by?
The amount of carbon dioxide in the blood
Breathing isn’t influenced by O2 concentrations except when…. give an example
O2 is very low, such as extreme altitude change
What is the process of measuring lung volume? What is the graph showing the results called?
Spirometry and is shown on a spirogram
What is tidal volume (VT)? What is the normal amount for a person?
Volume of air inhaled during a single breath, ~500ml during normal breathing
What is functional residual capacity (FRC)? What is the normal amount for a person?
Volume of air left in the lungs after a normal exhalation, ~2500ml
Functional residual capacity is a useful measurement to indicate what?
some types of pulmonary disease
How can it be measured?
Breathing in a gas such as helium (not absorbed by the body) and measuring its dilution
What is the formula to calculate the FRC?
FRC = V(c1-c2)/C2
- V*c1 = amount of He in container initially
- V*c2 = amount of He in container
- c1/2 = concentration of helium initially/finally
What does the FRC formula assume?
Conservation of mass
What is dead space?
The portion of lungs where gas exchange does not occur
What is anatomic dead space? What is a rough estimate in a normal person?
- airways where there are no alveoli present
- ~mls of dead space = body mass in pounds
What is alveolar dead space? What is a normal amount in a person? What can cause it to increase?
- Alveoli that don’t get blood supply
- normally less than 5ml but disease can increase it
What is physiological dead space?
anatomic + alveolar dead space
What causes the diffusion of O2 and CO2 between the lungs and the air, organs and blood?
Difference in partial pressure of O2 and CO2
What is the partial pressure?
The pressure exerted by a particular gas in a mixture of gases
What is partial pressure equal to?
The product of the volume fraction of the gas in the mixtures and the total pressure of the mixture of gases
How do the partial pressures in the air, blood and body tissue allow for gas transfer?
- Blood arriving in lungs has low partial pressure of O2 and high partial of CO2, air has higher partial pressure of O2 and lower CO2 so O2 diffuse from air into lungs, CO2 from lungs into air
- Tissue has lower partial pressure of O2 than lungs and higher partial pressure of CO2 so O2 goes from lungs to tissue, CO2 from tissue to blood
How is oxygen transported in the blood?
Red blood cells contain a protein called haemoglobin which has a strong attraction for O2
How many O2 molecules can each haemoglobin molecule carry?
4 O2 per haemoglobin molecule
When all the haemoglobin is bonded to max O2, what is this called? How much O2 can be carried by the blood?
- Haemoglobin is fully saturated
- 0.2L O2 per 1L of blood
What is the O2 saturation when blood leaves the lungs?
100%
When resting, what does the O2 saturation drop down to when returning to the lungs? What about when doing exercise?
rest = 75% exercise = 20%
What does an O2 - haemoglobin disassociation curve show?
how the haemoglobin saturation varies with the partial pressure of oxygen
On the O2 - haemoglobin disassociation curve it is very steep from ~40 mm Hg PO2 (partial pressure of O2), what does this indicate and how is this beneficial?
- Show that for a small change in partial pressure there is a large change in O2 saturation
- This means that during exercise when the partial pressure drops only a little bit, there is a large amount of O2 that is supplied
