Exam 3 -- Lecture 1 Flashcards
What is compliance?
distensibility of the lung and chest wall
What does lung compliance depend on?
amount of elastic tissue
When you breath in, the thoracic cavity becomes larger and the pressure in the thorax pressure RISES/FALLS?
pressure falls; allowing lungs to expand and fill
When alveoli are filled to their limit, are they MORE/LESS compliant?
less compliant; stiffer
When you breath out, the thoracic cavity becomes smaller and the pressure in the thorax pressure RISES/FALLS?
pressure increases; forcing air out of lungs
What is the relationship of compliance with volume and pressure?
compliance is proportional to volume
compliance is inversely proportional to pressure
What is hysteresis?
pressure and volume are different for inspiration vs expiration
Why does the pressure volume curve look different for inspiration vs expiration?
different surface tensions at air-liquid interface of lungs
* air-liquid interface is special
Its difficult for alveoli to expand because there is a strong molecular force holding liquid in them together, what solves this problem?
surfactant
What cells make surfactant?
type II alveolar cells
What is surfactant made of ?
phospholipids
How does surfactant work?
breaks the surface tension allowing lungs to expand/inflate rapidly
Exhaling is a passive process so as you exhale lung surface area decreases faster than surfactant can be removed so the density of surfactant in epithelial fluid __________ and the curve is fairly flat. However as lung volume decreases, surfactant is removed and surface tension begins to ___________ again.
increases
increase
Why does the saline inflation of a lung has more compliance?
doesn’t have to get past air-fluid interface to break surface tension
What is the law of LaPlace?
attractive forces between molecules of liquid causes small alveoli to have very high surface tension that is hard to overcome
What is the relationship between pressure and radius?
inversely proportional
- larger radius alveoli = lower pressure (easier to keep open)
SMALL/LARGE alveoli make it harder to breathe
small
Smaller alveoli make it harder to breath but they are required for…
gas exchange (increased surface area)
The smaller the alveoli the LARGER/SMALLER the pressure
larger
_____ is the substance that keeps small alveoli open and available for gas exchange
surfactant
Without surfactant atelectasis would happen, what does that mean?
small alveoli would collapse
Does surfactant increase or decrease lung compliance?
increase (reduces work required)
What secretes surfactant lipids in type II alveolar cells?
lamellar bodies
If lungs were deficient in surfactant, would the opening pressure be higher or lower?
higher
If lungs were deficient in surfactant, would it be easier or harder to inflate?
harder
If lungs were deficient in surfactant, would the deflation stability be better or worse?
worse
If lungs were deficient in surfactant, would the lung volume increase or decrease?
decrease
If you have increased compliance, will the line on a pressure volume curve move left or right?
left
easily breathe in & harder to breathe out (increased volume with lower pressure)
If you have decreased compliance, will the line on a pressure volume curve move left or right?
right
harder to breathe in & easier to breathe out
(decreased volume with higher pressure)
What is a disorder that has increased compliance?
emphysema/COPD
What is a disorder that has decreased compliance?
fibrosis
In emphysema, is it harder to breath in or out?
harder to breathe out
In fibrosis is it easier to breath in or out?
harder to breathe in
Why is there an increase in compliance in emphysema/COPD?
loss of elastic fibers causes difficulty in contracting lungs to breathe out but they fill easily
Why is there an decrease in compliance in fibrosis?
build up of scar tissue causes difficulty pulling air in to expand lungs but they exhale easily
What is the condition NRDS?
lack of surfactant
common in premature babies
Is the pressure normally in the pleural space positive or negative and why?
negative
parietal pleura are attached to chest wall and are being pulled outwards
HELPS HOLD LUNGS OPEN
If there is a puncture in the pleura the lungs ________ and the chest wall ________
collapse
springs out
What are the 3 types of pneumothoraxes?
closed
open
tension
What is a closed pneumothorax?
damage to lungs causing air to leave lungs and into the pleural space
In a closed pneumothorax, the pleural space pressure is <, >, = atmospheric pressure?
pleural pressure < atm
What is an open pneumothorax?
damage to chest wall causing air to rush from outside into pleural space cavity
In an open pneumothorax, the pleural space pressure is <, >, = atmospheric pressure?
pleural pressure = atm
What is a tension pneumothorax?
damage to chest wall but flat covers hole resulting in air building up in pleura space because it cannot leave
air comes in pleural space but cannot come out
In a tension pneumothorax, the pleural space pressure is <, >, = atmospheric pressure?
pleural pressure > atm
What is so life threatening about a tension pneumothorax?
pressure of chest can push on heart lowering cardiac output and venous return resulting in shock
What is the normal value for PA O2?
(alveolar)
104 mmHg
What is the normal value for Pa O2 in systemic arterial blood?
(arterial)
100 mmHg
What is the normal value for PA CO2?
(alveolar)
40 mmHg
What is the normal value for Pa CO2 in systemic arterial blood?
(arterial)
40 mmHg
What is the normal value for Pa CO2 in mixed venous blood?
(arterial)
46 mmHg
What is the normal value for Pa O2 in mixed venous blood?
(arterial)
40 mmHg
What 3 reasons are the PA O2 is lower than atmospheric air?
- water vapor reduces amount of O2
- some old air left in alveolar
- Co2 being taken up into alveolar dilutes O2 levels
Pulmonary circulation is the output of the _______ ventricle
right
Is pulmonary circulation a high or low pressure system?
low pressure
How is pulmonary flow regulated?
change in resistance in pulmonary arterioles
What is the most important regulator of pulmonary flow?
PA O2 (alveolar pressure of O2)
If PA O2 falls, resistance INCREASED/DECREASES and blood flow RISES/FALLS.
resistance increases
flow falls
* doesn’t seem right but its because blood flow diverts flow hypoxic alveolar to ones that work
When PA O2 drops why does the resistance there increase and blood flow decreases?
want to divert blood away from hypoxic alveoli to ones that work
Gas exchange relies on a __________
gradient
Why is distribution of blood flow uneven in the lungs?
gravity
Where is blood flow the lowest in the lungs?
zone 1 (apex)
Where is blood flow the highest in the lungs?
zone 3
In zone 1 of the lungs, PA ___ Pa ___Pv
PA > Pa > Pv
In zone 2 of the lungs, Pa ___ PA ___Pv
Pa > PA > Pv
In zone 3 of the lungs, Pa ___ Pv ___PA
Pa > Pv > PA
Why is ventilation in zone 1 of lungs lowest?
alveoli get filled first so they are largest = less compliant = decreased blood flow (alveoli pushing on vessel)
* see slide 27
Why is ventilation in zone 3 of lungs highest?
alveoli are filled last so they are small = more compliant = increased blood flow (alveoli aren’t pushing on vessel)
* see side 27
Why is there a difference in the extent of ventilation in the lungs?
mixture of compliance, weight on lungs, and gravity
What alveoli experience greater change in volume and are better ventilated?
zone 3
What alveoli have more of a negative intrapleural pressure?
zone 1
expand the most
What part of the lungs in the least compliant?
apex (zone 1)
Blood flow and ventilation are the highest where in the lungs?
bottom
V/Q (ventilation/perfusion) ratio is highest at the top or bottom of the lungs?
top
Why is the V/Q ratio highest at the top of the lungs?
more ventilation but less perfusion at top
large V / small Q
What is the normal V/Q ratio?
0.8
What 4 components control breathing?
- brainstem
- chemoreceptors
- mechanoreceptors
- respiratory muscles
What 2 structures in the brain stem control breathing?
medulla
Pons
The dorsal side of medulla controls inspiration or expiration?
inspiration
The ventral side of medulla controls inspiration or expiration?
expiration
The dorsal respiratory group controls what?
rhythm of inspiration (send signals to diaphram to contract)
The dorsal respiratory group receives input from what?
pre-Botzinger complex
Where does the dorsal respiratory group send its message?
diaphragm (to increase contractions)
The ____________ respiratory group is not very active during quiet breathing why?
ventral
expiration is a passive process
When does the ventral respiratory system become active?
exercise
The ventral respiratory system plays a role in the ______ reflex via the pre-Botzinger complex
sigh
What are the 2 pontine (Pon) centers?
apneustic center
pneumotaxic center
What is the apneustic center?
(1 of the pontine centers) “stimulatory” causes prolonged inspirations and short expirations
What is the pneumotaxic center?
(1 of the pontine centers) “inhibitory” shuts off DRG thereby controlling volume of inspiration
Do central chemoreceptors communicate with inspiration or expiration centers?
inspiration centers
What gas primarily controls the medulla chemoreceptors?
CO2
Central chemoreceptors are most sensitive to changes in _____
pH
What enzyme catalyzes the reaction of CO2 + H2O —> H2CO3 —> H+ + HCO3-?
carbonic anhydrase
What gas is permeable across the BBB and is important for central chemoreceptors?
CO2
Can the CO2 + H2O —> H2CO3 —> H+ + HCO3- reaction occur in the CNS?
yes; this is how central chemo receptors sense changes in pH
Peripheral chemoreceptors are most senstitive to decreases in arterial _______
Pa O2
As blood CO2 increases, pH of CNS increases/decrease which is sensed by central chemoreceptors?
decreases
When blood CO2 increases, pH of CNS decreases which is sensed by central chemoreceptors which sends a message to DRG to increase/decrease breathing.
increase breathing
Where are peripheral chemoreceptors located?
carotid bodies and aortic arch
What are peripheral chemoreceptors most sensitive to changes in?
O2
Carotid body (peripheral chemo)receptors responds to Pa O2 < ______ mmHg
60
What receptor receives more blood than any other organ?
peripheral chemoreceptors
Activation of peripheral chemoreceptors increases/decreases the rate of breathing?
increases
What activates peripheral chemoreceptors?
drop in O2
Decreases in pH are mediated only by peripheral receptors in __________
carotid bodies
Sensory information received at peripheral chemoreceptors is relayed to __________
DRG
What are mechanoreceptors?
receptors that sense stretch in muscles (of lungs or limbs)
What is the Herin-Breur reflex?
mechanoreceptors in lungs sense stretch and initiate creased breathing rate by increasing expiration
Mechanoreceptors in limb muscles and joints sense movement and instruct __________ center to increase breathing rate
inspiratory center
Mechanoreceptors in the limbs are part of the ___________ response to exercise (feed-forward)
anticipatory
What do irritant receptors do?
in between epithelial cells in airways that cause constriction of bronchial muscles to increase breathing rate
What do J receptors do?
in alveolar walls that sense growing of capillaries and will increase interstitial fluid volume = decreased breathing rate
What zone is pressure highest in the lungs?
zone 1 (apex)
alveolar pressure is highest, and pulmonary blood flow is limited
What central control center controls holding breath?
pneumotaxic
Where are the central chemoreceptos located?
under medualla
If you increase dead volume is it harder or easier to breath and why?
harder
increases resistance
If an airway has a smaller radius, does the resistance increase or decrease?
increased resistance
