Pulmonary/Respiratory pt.2 Flashcards
lungs are composed of __________
elastic and inelastic properties
how do the elastic components of the lungs play a role in its function
the stretch(inspiration) and recoil(expiration) of these components play a role in lung compliance
explain the significance of the surface tension of water in the fluid lining the alveoli
the surface tension of water in the fluid lining the alveoli plays a major role in lung compliance with the strong attraction of water molecules to each other tending to pull alveoli shut
surfactant
a compound which aids in the prevention of lung collapse as a result of water tension
- > composed of the phospholipid dipalmitoylphosphatidylcholine (DPPC)
- > surfactant prevents the total colapse of lungs by decreasing the surface tension of water
pressures within the lung are ALWAYS compared to __________
atmospheric pressure (Patm)
= 760 mmHg
- > calculated as ΔP
intrapulmonary pressure
Ppul
Ppul at rest = atmospheric pressure so ΔP = 0 mmHg
- > however, Ppul varies during respiration such that Ppul is less than Patm during inspiration and greater than Patm during expiration
describe the pressures inside the alveoli as lung volumes increases and decreases
as lung volume increases (alveoli open/stretch), pressures within the alveoli decrease
as lung volume decreases (alveoli recoil), pressures within the alveoli increase
transpulmonary pressure; what happens when this increases
measure of distending force across the lungs
- > an increase in Transpulmonary P = greater distending P across the lungs and the alveoli expand
intrapleural pressure at rest
Pip
at rest = -4 mmHg
Pip does vary during respiration but is always negative during normal breathing; postive reading can indicate a collapsed lung
describe lung volume during inspiration and what happening as it occurs
- > increased V occurs duing inspiration
- > elevation of ribs by the external intercostals = increasing anterior-posterior diameter of the chest
- > downward movement of the diaphragm (contraction) = lengthening of the chest cavity
describe pressure within the lungs during inspiration
- > as lung volumes increase, pressure within the lungs (Ppul) decreases and is now less than Patm by -1 mmHg
- > this creates a “vacuum” effect due to a pressure gradient (higher pressures outside the lungs than inside)
- > therefore, air moves from an area of high pressure (outside) to and area of low pressure (inside) filling the lungs with air until the outside P = inside P
describe lung volume during expiration
a decrease in V occurs during expiration
- > relaxation of external intercostals + upward movement of the diaphragm + elasetic recoil properties of the lungs decreases lung volume snd thorasic cage volume
* relaxation of the respiratory muscles stop the physical pull on the alveoli, causing the walls of the alveoli to recoild and “close” the alveoli
describe pressure during expiration
as lung volumes decrease, pressure within the lungs increases (increased Ppul) and is now greater than Patm by +1 mmHg
- > pressure gradient is now from inside to outside and air flows from inside the lungs to outside the lungs until the pressure within the lungs = atmospheric pressure
what is Daltons law
each gas contributes to total atmospheric pressure in direct proportion to its relative concentration
- > therefore in a mixture of gases, the pressure exerted by each gas is independent of the pressure exerted by others
explain the ambient conc. of O2 and PAO2 and PaO2
the O2 we breath in only makes up 21% of total atmospheric pressure, and 21% of 760 mmHg = 160 mmHg (ambient air concentration of O2)
- > but inside the alveolus, changes occur such that the partial pressure (PAO2) of O2 decreases to around 104 mmHg
- > arterial partial pressure (PaO2) of oxygen is usually around 100 mmHg while tissue PO2 can be as low as 40 mmHg in the resting state
changes to the partial pressure of O2 within the alveolus can be caused by what
- temperature
- humidity
- CO2 mixing with incoming air
ventilation
= frequency (RR) x depth of breathing
- > around 10-20 breaths/min
RR = respiratory rate
total ventilation (at rest)
VT
= amount inspired/breath x RR
= tidal volume (TV) x RR
TV = 6000 cc/min
dead space ventilation
VD
amount of each TV that remains in the non-gas-exchanging portions of the airways
dead space minute ventilation = 150 cc/breath x 12 breaths/min
- > = 1800 cc/min (amount of each ventilatory intake that is lost in the non gas exchaning portions of the lungs)
Alveolar Ventilation
VA = VT - VD
- > provides the 104 mmHg of PO2 for the alveoli and the 100 mmHg of PO2 for the arteries
= 6000cc/min - 1800cc/min = 2400cc/min
normal at rest value of VA, VT, VD and the ratio of dead space minute ventilation to total ventilation
total ventilation/min = 6000cc
dead space ventilation/min = 1800cc
alveolar ventilation/min = 4200cc
dead space minute ventilation to total ventilation = 1800/6000 = 0.3
IRV vs ERV
Inspiratory reserve volume
- > the max volume of air that can be increased above tidal volume
Expiratory reserve volume
- > the expiration of a volume of air after resting tidal volume has been expired
what is RV and why is it useful
residual volume
- > volume of air remaining in the lugs after maximal expiration
- > helps hold alveoli open and prevent lung colapse
- > an increased RV can indicate loss of elastic tissue which leads to decreased recoil of the lungs
FVC
forced vital capacity
- > maximal volume of air a person can expire after maximal inspiration
- > IRV + TV+ ERV
FEV1
forced expiratory volume in 1 second
- > maximal volume of air that can be exhaled in 1 sec following maximal inspiration
FER
forced expiratory ratio = FEV1 /FVC
- > healthy individuals with good lung function can expire around 80% of their vital capacity in 1 sec
- > the FEV1 /FVE ratio is used to help determine the level of functional loss in an individual
Medullary respiratory centre
controls both inspiration and expiration and contains the dorsal respiratory group (DRG) neurons and the ventral respiratory group (VRG) neurons
respiration
respiration = reflex activity
describe the DRG neurons during resting/quiet breathing
- > neurons of the DRG appear to integrate information from the peripheral stretch receptors and chemoreceptors and communicates that information to the VRG
describe the VRG during resting/quiet breathing
- > the VRG contains inspiratory neurons that excite the diaphragm and external intercostals resulting in the V and P chnages for inspiration to occur
- > within the VRG is a rhythm generator composed of pacemaker cells that set basal/quiet breathing rates
what happens during resting/quiet breathing once inspiratory muscle contration and inspiration have occured
signals to the spinal motor neurons cease and the external intercostals and diaphragm relax = passive expiration
eupnea
normal, unlaboured breathing
- > around 2 seconds in inspiration and around 3 seconds in expiration (12-15 breaths/min)
describe active/increased ventilation
- > with increased ventilation, the VRG expiratory neurons send signals to the expiratory muscles (internal intercostals, external abdominal obliques and the rectus abdominus) resulting in contraction of these muscles and increased release of air from the lungs
- > the inspiratory and expiratory muscles in active breathin are activated alternately
explains the pons control of the medullary inspiratory neurons
- > the pontine respiratory centres found within the pons, modify the activity of the medula
- > impulses from the pontine centres to the VRG influences the transition between inspiration and expiration
* some ventilation is under voluntary control (i.e. coughing, singing) and controled by the centres in the thalamus and cerebral cortex (brain) of the CNS which sends input to the pontine respiratory centres
which processes set/determine respiration rhythm
it’s set by several processes
- specialized inspiratory neurons that act as pacemaker neurons
- > although such neurons have be found, loss of these pacemakers doesn’t stop respiration - reciprocal inhibition of the interconnected neuronal networks in the medula
- > most likely there are 2 sets of pacemaker neurons that inhibit each other and cycle that inhibition to set te rhythm
how is inspiration depth alterned
inspiration depth is altered by how actively (frequency of stimulus) the respiratory centre stimulates the motor neurons serving the respiratory muscles
- > increased depth of each breath gives you increased ventilation
what is RR
rate of respiration
- > how long the inspiratory centre is active or how quickly it is switched off/ moves to expiration
different ways RR can be suppressed and what happens when it is completely suppressed
suppression of the inspiratory centre can occur with…
- > sleeping pills, morphine, alcohol, polio
complete suppression of inspiration results in cessation of breathing (apnea)
respiratory centres require input from which receptors to monitor blood chemistry
- Central chemoreceptors
- peripheral chemoreceptors
- pulmonary receptors
what are central chemoreceptors and how do they react to change
- > respond to changes (CO2 levels) in brain extracellulaar fluid (ECF)
- > stimulated by an increase in blood CO2 above the normal 40mmHg via increased blood H+ levels
- > the increased free H+ = decreased blood pH which stimulates the central chemoreceptors to send information to the respiratory regulatory centres
- > this stimulation results in increased ventilation (increased depth and rate) which will result in increased release of CO2 from the body (causes decreased [H+])
what are peripheral chemoreceptors and how do they react to change
- > peripheral chemoreceptors help maintain ventilation when the central chemoreceptors (brain centres) have become hypoxic and unable to function
carotid body chemoreceptor
- > monitor arterial PO2 (normal PO2 of arteria blood is 100mmHg) and a decrease of PO2 below 60mmHg will trigger increased ventilation
aortic body chemoreceptors
- > monitor the O2 rich blood released from the LV
hypercapnia
increased blood CO2 levels
major terms we should know (respiratory)
pulmonary receptors
- > receptors in the lungs that respond to a variety of irritating factors (i.e. smoke, pollutants, excess mucus)
- > these communicate with the respiratory centres - inititate coughing
Cheyne - Strokes Breathing
periodic breathing with rise and fall patterns separated by periods of apnea
= result of impaired central feedback mechanisms (need to accumulate large accumulate large arterial concentrations of CO2 to trigger expiration)
