RESP-pulmonary ventilation and breathing Flashcards
what are the 4 types of pressure?
- atmospheric pressure
- trans-pulmonary pressure
- intra-pleural pressure
- pulmonary/ intra-alveolar pressure
what is atmospheric pressure?
pressure of air outside the body
what is trans-pulmonary pressure?
the difference in intrapulmonary and intra-pleural pressure
should trans-pulmonary pressure always be positive or negative?
positive
what is intra-pleural pressure?
pressure intra-pleural space (between parietal and visceral pleura)
should intra-pleural pressure always be positive or negative?
negative
what happens to intra-pleural pressure upon inspiration?
becomes more negative
what is pulmonary/ intra-alveolar pressure?
pressure inside the lungs/ alveoli
what happens to the pressure in inspiration?
intrapulmonary pressure < atmospheric pressure
=air moves into lungs
what happens to the pressure in expiration?
intrapulmonary pressure > atmospheric pressure
=air moves out of lungs
which pressure should always be the the lowest value?
intra-pleural pressure
how does air always move?
-down pressure gradient (from high to low)
what is breathing also called?
pulmonary ventilation
what is inspiration?
breathing in
what is expiration?
breathing out
how is breathing accomplished?
by changing the lung/ thoracic cavity volume
what are the requirements of the thorax for breathing?
- must be rigid enough for protection
- yet flexible enough to act as bellows for breathing
is inspiration active or passive?
active process
how is inspiration initiated?
by the respiratory control centre in the medulla oblongata
what does the activation of the medulla do in inspiration?
- causes contraction of diaphragm and external intercostal muscles
- Leads to an expansion of the thoracic cavity and a decrease in the pleural space pressure
is expiration an active or passive process?
passive-due to elastic recoil of lungs
are there any exceptions to expiration being passive?
-If a lot of air has to be removed quickly (eg. during exercise) the internal intercostal muscles and abdominal muscles contract and accelerate expiration by raising pleural pressure
how do pressure differences between the 2 ends of the conducting zone occur?
due to changing lung volumes
what are 3 important properties of lungs?
- compliance
- elasticity
- surface tension
what is recoil pressure?
measure of elastic forces in the lungs that tend to collapse the lungs at each instant of respiration
describe the mechanism of inhalation
- the volume of the thoracic cavity increases
- ->vertically when diaphragm contracts and flattens
- ->laterally when ICs raise ribs
- vol increases/ intrapulmonary pressure decreases
- air moves into lungs
when does inspiration begin?
inspiration begins as the diaphragm contracts
which muscle is the strongest muscle of exhalation?
rectus abdominis
describe the mechanism of exhalation
- the volume of the thoracic decreases..
- ->vertically when diaphragm recoils and domes
- ->laterally when ICs passively relax (or muscles of forces expiration lower ribs)
- vol decreases/ intrapulmonary pressure increases
- air moves out of lungs
name the muscles of forced inspiration
- sternocleidomastoid
- scalenes
- pectoralis major
name the muscles of quiet inspiration
- external ICs
- diaphragm
name the muscles of forced expiration
- internal ICs
- external oblique
- internal oblique
- transverse abdominis
- rectus abdominis (strongest)
does quiet respiration require muscular effort? why?
no
-it is achieved by ribs and diaphragm returning to their resting state
what are the roles of the conducting airways?
- humidify air
- warm air
- secrete mucous
- protect lungs from air particles
which structures of the respiratory system make up the conducting airways?
- trachea
- primary bronchus
- secondary bronchus
- tertiary bronchus
- terminal bronchus
- conducting bronchiole
- terminal bronchiole
which structure of the conducting airway is the first without any cartilage?
conducting bronchiole
which structures make up the respiratory airways?
- respiratory bronchiole
- alveoli
what are the roles of the respiratory airways?
- gas exchange
- surfactant secretion
inspiration begins as…
A-the lungs contract B-the external IC muscles contract C-the lateral volume of the thoracic cage decreases D-the diaphragm relaxes and domes E-the diaphragm contracts and flattens
E
during inspiration…
A-atmospheric pressure< intrapulmonary pressure
B-intrapleural pressure>intrapulmonary pressure
C-transpulmonary pressure< atmospheric pressure
D-atmospheric pressure = intrapulmonary pressure
E-intrapulmonary pressure = intrapleural pressure
C
which of the following is NOT a muscle of exhalation?
A-sternocleidomastoid B-internal oblique C-external oblique D-transversus abdominis E-internal ICs
A
which of the following is the only one which does NOT require muscular effort?
A-quiet inhalation B-quiet exhalation C-forced inhalation D-forced exhalation E-they all require it
B
what is tidal volume (TV)?
the amount of air in a single inspiration or expiration
what is functional residual capacity (FRC)?
the volume of air that remains in the lungs at the end of normal respiration
what is vital capacity (VC)?
the volume of air that can be exhaled after a maximal inspiration
what is the name for the amount of air remaining in the lungs after maximal expiration?
residual volume (RV)
what is the name for the maximum volume of air in the lungs after a maximal inspiration?
total lung capacity (TLC)
what is the typical tidal volume (TV) value?
500ml
what is the typical VC value?
4800ml
what is the typical FRC value?
2400ml
what is the typical RV value?
1200ml
how many lung volumes are there?
4
which lung volumes can spirometry measure?
- inspiratory reserve volume
- tidal volume
- expiratory reserve volume
how many lung capacities are there?
4
what are lung capacities?
combinations of lung volumes
what is the most important lung capacity measurment?
VC
what is forced vital capacity (FVC)?
volume of air that can be forcibly blown out after full inspiration (litres)
what is forced expiratory volume (FEV1)?
volume of air that can be forcibly blown out-in one second-after full inspiration (litres)
what is laminar flow?
the smooth passage of air out of the airways
what are the (FEV1 and FVC) spirometry results of a healthy person?
- FEV1 % predicted > 80%
- FVC % predicted > 80%
FEV1:FVC ratio= 0.7-0.8
describe how the flow-volume loop appears in a healthy person
1-exhalation begins as sharp peak (air leaving trachea)
2-exhalation continues by the vol of air leaving at a steadily decreasing rate (air leaving bronchi)
3-negative loop backwards is the person inspiring air
what are the 2 types of respiratory disease detected by spirometry?
- obstructive
- restrictive
what are the spirometry values for FEV1 and FVC characteristic with obstructive disease?
FEV1: FVC ratio < 0.7
-FEV1 % and FVC % not required if ratio less than 0.7
what is the shape of the time-flow loop of a patient who suffers from obstructive disease?
- scalloped shape
- ->difficult for air to leave the airways because of obstruction
- ->but eventually all air leaves
what are the spirometry values for FEV1 and FVC characteristic with restrictive disease?
FEV1 : FVC ratio =normal (0.7-0.8)
FEV1 % predicted reduced (<80%)
FVC 5 predicted reduced (<80%)
(both reduced so ratio not affected)
what is the shape of the time-flow loop of a patient who suffers from restrictive disease?
- normal shape but cute short
- ->not all air leaves airways
- ->lung tissue is too stiff or ribs/ muscles are ineffective and too weak for forced expiration
what are the limitations of spirometry?
- dependent on patient cooperation and effort
- since results are dependent on patient cooperation, lung vol (FVC) can only be underestimated, never overestimated
- usually repeated at least 3xx to ensure reproducibility, each FVC result within 5% or less than 150ml variation
- stable asthmatics have normal spirometry between acute exacerbation, limiting spirometry’s usefulness as a diagnostic tool
- look at flow vol loop to assess quality and effort of the test (not always available in some commercial spirometers)
What are some other diagnostic tests for respiratory conditions?
- VO2 max
- Respiratory muscle strength
- Diffusion capacity
what are some example of people voluntarily controlling their breathing?
- singing
- speaking
- yelling
- holding their breath
which part of the brain is involved in voluntarily controlling your breathing?
cerebral cortex
what is the effect of an increase in body temperature on respiration rate?
will involuntarily increase respiration rate
what are the 2 groups the medullary centre is split into?
-ventral respiratory group (VRG)
-dorsal respiratory group
DRG
what is the role of the ventral respiratory group (VRG)?
- inspiration and expiration
- forceful breathing only
what is the role of the dorsal respiratory group (DRG)?
- inspiration only
- quiet and forceful breathing
what are the 2 types of breathing?
- quiet (normal) breathing
- forceful breathing
what is the Pre-Botzinger complex?
- structure in the VRG
- helps modulate the rhythm of breathing
- similar to a pacemaker
what happens when the DRG activates?
- activates for 2 seconds
- diaphragm contracts via phrenic nerve (c3-5)
- external IC muscles contract via IC nerves (T1-T11)
=quiet inspiration
what happens when the DRG deactivates?
- deactivates for 3 seconds
- diaphragm relaxes
- external IC muscles relax
=quiet (passive) expiration
describe the neural control of forced inhalation
-DRG activates
(diaphragm contracts/ external IC muscles contract via IC nerves)
-VRG activates
(accessory muscles of inhalation C1-3-sternocleidomastoid, scalene, pectoralis minor contract)
=forceful inhalation
describe the neural control of forced exhalation
-VRG activates accessory muscles of exhalation
(external oblique, transversus abdominus, rectus abdominis)
and internal IC
(via IC nerves) contract
=forceful exhalation
what is the pontine respiratory centre responsible for?
modifying the basic rhythm of breathing when exercising, sleeping and speaking
when is the pontine respiratory centre active?
during any type of respiration
what are the 2 centres associated with the pontine respiratory centre?
- apneustic centre
- pneumotaxic centre
where is the apneustic centre located?
lower pons
where is the pneumotaxic centre located?
upper pons
what is the role of the apneustic centre?
- stimulates inspiratory centres in the medulla
- sends signals for longer and deeper breaths
- “apneuses” ->gasps
what is the role of the pneumotaxic centre?
- inhibits inspiratory centres in the medulla and the apneustic centre
- sends signals for shorter and shallower breaths
what is the role of mechanoreceptors in influencing neural control?
prevent over-inflation of the lungs
where in the respiratory system are mechanoreceptors located?
located in the bronchi
describe the Hering-Brewer reflex.
1-stretching causes activation of mechanoreceptors
2-receptors send inhibitory signals to the DRG (inspiration) via the vagus nerve
3-inspiration stops
4-expiration begins, reducing the amount of stretch and deactivates the mechanoreceptors-the vagus nerve no longer inhibits the DRG
5-inspiration allowed to begin (basic negative feedback loop)
what is the role of chemoreceptors in influencing neural control?
-monitors levels of O2, CO2 and pH and influences respiration accordingly
what are the 2 types of chemoreceptors?
- peripheral
- central
where are peripheral chemoreceptors located?
in the bifurcation of the aorta into the carotid artery and the aortic arch
what is the role of peripheral chemoreceptors?
- monitors levels of O2
- modulates respiratory centres (DRG and VRG) via vagus nerve and glossopharyngeal nerve
where are central chemoreceptors located?
on the surface of the medulla and are exposed to CSF
what is the role of central chemoreceptors?
- directly monitors H+
- indirectly monitors levels of CO2 to modulate respiratory centres (DRG and VRG)
- CO2 + H2O H2CO3 H+ + HCO3-
what are the components of haemoglobin
- protein which contains 4 haem groups
- also contains 4 globin groups
what happens to Hb as one O2 molecule binds?
Co-operative binding
->binding of 1st O2 molecule causes conformational change making ti easier for the other 3 O2 molecules to bind
what is formed as O2 binds to the haem group?
oxyhaemoglobin
where does o2 bind to Hb and where is it unloaded?
- binds in lungs
- offloads at body tissues
which molecule binds to the globin group of Hb?
CO2 (x4)
what is formed when co2 binds to Hb?
carboxyhaemoglobin
where does co2 bind to Hb and where is it unloaded?
- binds in body tissues
- offloads in lungs
where is the majority of co2 dissolved?
the plasma
what % co2 is bound to Hb?
23%
The dissolving of co2 in the blood is in equilibrium. What happens to the equilibrium in the body tissues?
the equilibrium shifts right
->to produce more H+ + HCO3-
The dissolving of co2 in the blood is in equilibrium. What happens to the equilibrium in the lungs?
the equilibrium shifts left
->to produce more CO2 + H2O
what is the equation for when co2 reacts with h2o?
CO2 +H2OH2CO3H+ + HCO3-
what is the chloride shift?
when HCO3- leaves the blood cell and enters the plasma, Cl- ions enter the blood cell, to maintain an electrical balance
what is the Bohr effect?
high concentrations of H+ will cause HbO2 to give up O2
what is the Haldane effect?
HbO2 reduces the affinity of globin for CO2
CO2 does not bind easily if O2 has already been bound
Outline Boyle’s Law.
the volume of gas varies inversely with its pressure
Outline Dalton’s Law.
the total pressure is equal to the sum of partial pressures
Outline Henry’s Law.
the solubility of a gas in a liquid is dependent upon;
- > the partial pressures of gas in the air
- > the solubility coefficient of the gas in the liquid
which is more soluble co2 or o2 and what does this mean for O2 diffusion?
- CO2 is more soluble than O2
- >higher p(O2) required for O2 to diffuse
why is it necessary that in alveolar air and arterial blood-p(O2) is much higher than p(CO2)?
so that p(O2) is able to diffuse into blood
Outline Graham’s Law.
the rate of diffusion is:
- > directly proportional to the solubility coefficient of the gas
- > inversely proportional to the square root of its molecular weight
Outline Fick’s Law of Diffusion.
the amount of gas diffusing in (unit time) through the resistence of a barrier is:
- > directly porortional to the SA of the barrier, the diffusion constant (D) and the partial pressure on each side
- > indirectly proportional to the thickness of the barrier
what are the values for p(O2) either?
5kPa
or
13kPa
what are the values for p(CO2) either?
5kPa
or
6kPa
what does it mean for the o2-Hb dissociation curve when there is a higher p(O2)?
- more area under the curve
- Hb has higher affinity for o2
- O2 will more readily load onto Hb (e.g. in the lungs)
what does it mean for the o2-Hb dissociation curve when there is a lower p(O2)?
- less area under the curve
- eg in respiring tissues
- Hb has lower affinity for O2
- o2 more readily unload off Hb and onto respiring tissues
At what p(O2) is Hb saturated to 90%?
8kPa
what is the atmospheric p(O2) when Hb is 90% saturated?
13kPa
-means humans can still achieve 90% saturation even if they enter environments in which p(O2) drops by 6kPa
which conditions will increase p(O2) value (and therefore decrease affinity for O2 to Hb-shift curve right)?
- acidity (low pH causes o2 to be liberated-Bohr effect
- high co2-similar effects to low pH
- increased temp-heat is by-product of metabolic reactions-require more o2, o2 liberated more readily-more kinetic bonds
- increased 2,3DPG-substance found in RBCs causes o2 to bind less tightly to haem groups (via allosteric binding)
what does increased Hb O2 affinity mean for O2 unloading?
increased affinity= reduced unloading
what does decreased Hb O2 affinity mean for O2 unloading?
decreased affinity=increased unloading
which factors increase Hb’s O2 affinity?
- low temp
- low 2,3-DPG
- low H+ conc (high pH)
- foetal Hb
which factors decrease Hb’s O2 affinity?
- low pH (high H+ conc)
- high co2
- high temp
- high 2,3 DPG
