respiration 2 Flashcards
what is determined by the HbO2 dissociation curve?
the amount of O2 carried by Hb for a given partial pressure of O2
how is the curve at high values of P02/alveolar PO2 levels?
the curve is flat
how is the curve at low values of P02/peripheral tissue levels of PO2?
the curve is steep
what happens to the amount of O2 bound to Hb at high values of PO2?
the amount stays relatively constant
what happens to HB02 when alveolar PO2 drops from 100 mmHg to 80 mm Hg?
Nothing really, pressure needs to drop by 60 mm Hg in order for drop of HbO2 to be significant
what does a small drop of PO2 in peripheral tissues cause?
unloads O2 from Hb into the tissues
when does HbO2 dissociate more readily?
under low PO2 values
what happens if their is a drop in PO2 in peripheral tissues from 40 mm Hg to 20 mm Hg?
results in a decrease in %HbO2 from about 75% to 35%
a drop in PO2 is more significant in tissues or in the alveoli? why?
tissues are significantly more affected by drop in PO2. because it where metabolic processes requiring O2 take place
when blood enters tissue capillaries, which PO2 is greater; plasma or Interstitial fluid?
Plasma > intersitital fluid
what does O2 diffuse into from the capillary membrane? what does this cause?
diffuses into the interstitial fluid, which causes lowering of Plasma PO2
what happens to erythrocytes when plasma PO2 decreases?
O2 diffuses out of the erythrocytes into the plasma
what does the lowering of erythrocyte PO2 cause?
the dissociation of HbO2 into Hb and O2
what happens to the O2 when diffused into the interstitial fluid?
it will move into the cell
through what process are large amount of O2 from HbO2 brought into the cell?
via passive diffusion
at the end of the tissue capillaries, under resting conditions, how saturated is the Hb?
b is still 75% saturated
how can cells obtain more oxygen as needed during exercise?
due to the presence of myoglobin
what is the function of myglobin?
act as an intracellular carrier which facilitates the diffusion of oxygen throughout the muscle cell
what determines the affinity of Hb for O2?
the quaternary strucutre
what can increase the affinity of heme for O2? what is the process known as?
binding of a first O2 will increase affinity of heme binding to a second O2. this is known as cooperative binding
where is myoglobin found in?
skeletal muscle
how many O2 can myoglobin bind? hemoglobin?
1 O2 for myoglobin versus 4 O2 for Hb
how can the O2-myoglobin curve be described as?
hyperbolic in shape
when does myoglobin release its single O2?
only released under very low PO2
on what does the total amount of O2 in the blood depend on?
it depends on the Hb concentration
in what cases may Hb concentrations be reduced?
anemia
what is the Bohr Effect?
is the shift of the HbO2 dissociation curve to the right when blood CO2 or temperature increases, or blood pH decreases (
what is the logic behind the bohr effect?
when we exercise, we increase our CO2 and acid production and generate heat. The curve shifting to the right means that for a given drop in PO2, an additional amount of O2 is released from Hb to the working tissues
do the effects taken into account for the bohr effect have a high effect on amount of O2 if above 80 mm Hg
NO
what is 2,3-DPG
end product of red blood cell metabolism
when are levels of 2,3-DPG generally increased?
in cases of chronic hypoxia
what has an extremly high affinity for 02 binding sites in Hb?
CO (carbon monoxide)
what happens if CO binds to Hb?
reduces the amount of O2 bound to Hb and will shift O2-Hb curve to the left
what happens if the O2-Hb curve is shifted to the left?
decreases the unloading of O2 to the tissue.
why is there little stimulation to incrrease ventilation in CO poisoning?
because PaO2 remains normal
how much O2 is used and how much CO2 is produced per minute?
300 mL o2 used
250 mL CO2 produced
in how many different forms can CO2 be found in blood?
3 different forms
what forms can CO2 be found in blood?
- physically dissolved in the blood
- combined with Hb to form HbCO2
- as bicarbonate
what proportions of each form is CO2 found in the blood?
10% physically dissolved in the blood
- 11% combined with Hb to form HbCO2
- 79 %as bicarbonate
which law states that CO2 from tissues diffuses into the plasma where it is physically dissolved?
Henry’s Law
with what portion of Hb does CO2 bind? what portion does O2 bind?
CO2 will bind with the globin portion of Hb while O2 will bind with the heme portion
is there competition for binding of O2/CO2 to Hb?
no competition due different sites of interest
with what does CO2 bind to form bicarbonate?
bind with water
what enzyme aids the binding of CO2-H2O? when does this enzyme function?
carbonic anhydrase (CA) when CO2 diffuses into the erythrocytes
what happens if CO2 production is increased?
the production of HbCO2, HCO3-, and H+ increases
what happens if PCO2 is lowered?
HCO3- going to H2CO3 and further into CO2 and H2O and HbCO2 into Hb and CO2
when does PCO2 lower?
when venous blood flows through the lung capillaries
how is Hb in the tissue capillaries?
its free from O2
why is Hb free of O2 in tissue capillaries?
This occurs because reduced Hb is less acidic than HbO2. Hb acts as a buffer
what is reduced Hb?
HHb
what does the presence of reduced Hb aid in? what is this known as?
presence of reduced Hb in the tissue capillaries helps with the blood loading of CO2. this is known as the haldane effect
what is the haldane effect?
the fact that mixed venous blood can carry more CO2 than can arterial blood.
in what type of blood oxygenated or deoxygenated blood is there a greater [co2] being carried?
in deoxygenated blood
when does PCO2 lower?
when venous blood flows through the lung capillaries
what happens when PCO2 lowers?
HCO3- going to H2CO3 and further into CO2 and H2O, and HbCO2 generating Hb and CO2
how does the CO2 dissociation curve differ from the O2 dissociation curve?
no steep nor flat portion, mostly linear relationship between CO2 and PCO2
what happens if we hypoventilate and alveolar PCO2 increases?
then arterial, capillary, tissue and venous CO2 also rise
what happens to PCO2 if we double alveolar ventilation?
halves alveolat PCO2
what is the relationship between alveolar ventilation and CO2 removal?
propotional thus is one increases so does the other
when does respiratory failure occur?
when the respiratory system is unable to do its job properly
what may be some causes of respiratory failure?
- failure of gas exchanging capacities of the lungs
- failure of the neural control of ventilation
- failure of the neuromuscular breathing apparatus
what does blood hypoxia refer to?
deficient blood oxygenation (low PaO2 and low % Hb saturation)
what happens in hypoxic conditions if PaO2 decreases below 60 mm Hg?
O2 content in arterial and venous blood becomes lower than the normal values at sea level
what are the 5 general causes of hypoxia?
- inhalation of low PO2
- hypoventilation
- ventilation/perfusion imbalance in the lungs
- shunts of blood across the lungs
- o2 diffusion impariment
when is it possible to inhale low PO2?
in high altitudes
what happens to PaO2 and PaCO2 during hypoventilation
PaO2 decreases and PaCO2 increases
when does hypoventilation occur?
diseases affecting the central nervous system, neuromuscular diseases, barbiturates, other drugs and narcotics
when does Ventilation/perfusion imbalance in the lungs occur?
when the amount of fresh gas reaching an alveolar region per breath is too little for the blood flow through the capillaries of that region
why can hypoventilation be caused by shunts of blood across the lungs?
venous blood bypasses the gas exchanging region of the lungs and returns to systemic circulation, deoxygenated
in what cases can O2 diffusion be impaired?
thickening of the alveolar-capillary membrane, or pulmonary edema
what controls gas exchanges in our bodies?
the CNS
what type of control (voluntary/involuntary) is breathing under?
voluntary and involuntary control
what part of breathing is voluntarily controlled
hyperventilation
when part of breathing is involuntarily controlled?
while sleeping
what part of the brain is responsible for voluntary control of breathing?
the cerebral hemispheres
can the cerebral hemisphere be effective even when automatic control no longer functions?
yes
what part of the brain is responsible for involuntary control of breathing?
brainstem
why does your breath start again even if you try to forcefully prevent it?
this occurs because the arterial PCO2 has reached about 50 mm Hg and arterial PO2 has reached about 70 mm Hg thats when volontary control gets over ridden
what is the breaking point of respiration?
its when the volontary control of breathing is over ridden
how does the overriding of the voluntary control by the automatic control depends on?
depends upon the information from the receptors sensitive to CO2 and O2 levels
what are the 3 basic elements involved in the respiratory control system
- sensors
- controllers
- effectors
what is the function of sensors in respiratory control?
they gather information about lung volume and co2/o2 content
what types of sensors are used for in respiratory control
pulmonary receptors and chemoreceptors
the information from the sensors is sent to what?
to the controllers
where are the controllers of respiration found? via what?
in the pons and medulla via neural fibers
what happens once information reaches the controllers of the pons and medulla?
the peripheral information and inputs from the higher structures of the central nervous system are integrated.
as a result of of integration in the efforts of respiration what happens?
the neural impulses are generated and sent via spinal motoneurons to the effectors (respiratory muscles)
what is the function of the effectors of respiration?
allows for ventilation to be adapted to the person’s metabolic needs
what happens when demand for O2 and production of CO2 increases?
ventilation must therefore also increase
briefly summerize the relationship between the 3 basic elements of repsiratory control
sensors from lungs and chemoreceptors send signal to the central controlers (medulla and pons) which signal an output sent to the effector (respiratory muscles) to control respiration
what type of cell is contained in the medulla?
pacemaker cells
into what types of cells groups are the pacemaker cells of the medulla grouped into?
ventral respiratory and and dorsal respiratory group
what is contained in the ventral respiratory group of cells?
pre-botzinger complex
what is generated by the ventral respiratory group of cells?
generate basic rhythm
what do the ventral and dorsal respiratory cells connect to?
inspiratory motor neurones and connect to each other
what cells are responsible for turning off inspiration and causing a smaller tidal volume?
cells of the upper pons
what happens when inspiration is turned off yielding a smaller tidal volume?
increase in breathing frequency to maintain adequate alveolar ventilation
what happens if the pneumotaxic centres are cut?
breathing to become deep and slow
what are cells located in the lower pons known as?
apneustic center
what are cells located in the upper pons known as?
pneumotacxic center
what do the cells of the lower pons cause?
release of excitatory impulese to respiratory group of the medulla which promotes inspiration
what happens if influence from upper pons and vagus nerve is removed?
apneuses
in what cases are apneuses often seen in?
severe brain injuries
what are apneuses
tonic inspiratory activity interrupted by short expirations
what gets detected by chemoreceptors?
P02, PCO2, pH arterial blood
what happens if chemorecptors sens a change in pH or pressures?
ventilation will change in attempt to return to normal
where is info from the chemoreceptors carried to?
to the respiratory neurones
in what cases will activity of respiratory neurons increase?
PaO2 is too low (less than 60 mm Hg) or PaCO2 is higher than 40 mm Hg
in what cases will activity of respiratory neurones decrease?
PaO2 is higher than 100 mm Hg or PaCO2 is lower than 40 mm Hg
what are the different types of chemoreceptors?
central and peripheral
where are the central chemoreceptors located?
ventral surface of the medulla
what is the function of the central chemoreceptors
gives rise to the main drive to breathe under normal conditions
how can the sensitivity of central chemoreceptors be tested?
CO2 rebreathing test
what does the stimulation of central chemoreceptors increase?
minute ventilation and resulting hyperventilation will reduce PCO2 in blood and in the CSF
what causes the pH of the CSF to be reduced?
the presence of CO2
what happens when the pH of CSF decreases?
stimulation of centralc hemoreceptors
what are peripheral chemoreceptors sensitive to?
sensitive to changes in PO2, increases of PCO2 or decreased pH
where are peripheral chemoreceptors located?
in the carotid bodies and in aortic bodies
what makes up the carotid and aortic bodies
blood vessels, structual supporting tissue and numerous nerve endings
where do the afferent fibers of peripheral chemoreceptors project?
on the dorsal group of respiratory neurons in the medulla
how can effects of hypoxia be studied?
subject breathe gas mixtures with decreased concentrations of O2
what is normocapnia?
when levels of CO2 are normal in the blood
what can P02 be reduced to before significant changes to minute ventilation occur?
60 mm Hg
how can an augmented ventilatory response be obtained?
through an increase in pCO2 and decrease in PO2
what are the 3 types of receptors present in the lungs that respond to mechanical stimuli?
pulmonary stretch receptors
irritant receptors
juxta capillaries
where can pulmonary stretch receptors be found?
in the smooth muscle of the trachea to the terminal bronchiles
what innervates pulmonary stretch receptors?
large, myelinated fibers
how long are the pulmonary stretch receptors active for?
as long as the lung is distended
what happens to the pulmonary stretch receptors during inspiration?
phasically actived due to volume increase of the lungs
what is included in the chest wall?
rib cage
diaphragm
abdominal wall
are the lungs directly attached to the chest wall?
no, they are coupled by the visceral and parietal pleura
what is the pleural pressure (Ppl)?
the pressure that can be measured in the liquid-filled space between lung and chest
how is the Ppl at rest? why?
negative
due to the opposing forces acting on the lung and chest wall
what happens if a hole is punctured through the chest walls?
the lungs collapse and the chest springs outwards (pneumothorax)
what is measured to evaluate the elastic properties of the respiratory system?
measure changes in the recoil pressure of each separate structure for a given change in lung volume
what can measure lung volume?
spirometry
what measures the pressures of the respiratory system?
manometers or pressure transducers
what is a negative pressure refering to?
a pressure below Patm
what is the recoil pressure of a structure defined as?
he pressure difference between the inside and outside of the structure (transmural pressure)
what is the recoil pressure of the chest wall?
Pw=Ppl-Pbs
how can Ppl be measured?
measured using a flexible balloon introduced into the esophagus
why can a baloon be placed in the esophagus to determine pressure?
Because the esophagus is located between the two pleural spaces, esophageal pressure provides a close approximation of pleural pressure
how is transpulmonary pressure (Pl) measured?
Pl=Palv-Ppl
what is the trans-repsiratory system pressure (Prs)
Prs=Palv-Pbs
OR
Prs= Pl+Pw
what is compliance
refers to the ease with which each of these structures can be distended
how is compliance expressed as?
the volume change in the lungs for a unitary change in pressure
in the pressure-volume curve what does the slope represent?
compliance
what happens to the slope of the pressure-volume curve if The pressure required to maintain a given volume of gas inside the lungs increases as the volume increases
the slope must decrease
what happens to compliance in cases of diseases?
it can be altered
what does the pressure difference between the alveoli (Palv) and the pleural space (Ppl) equal
the pressure drop across the lung tissues
what does Palv-Ppl represent?
is the pressure required to maintain the lungs at a given inflation volume against their tendency to recoil elastically
what is elastance
1/complance
what produces the elastic recoil of the lunfs?
by the elastic lung tissue along with the forces of the liquid film lining inside the lungs
what is the thoracic compliance defined in terms of?
The compliance of the thorax is defined in terms of a change in thoracic volume ∆V and a change in pressure across the chest wal
what is the compliance of the respiratory system related to?
compliances of the lung and chest wal
what is the Prs at FRC?
zero because system is at rest
what happens to the lungs and chest at FRC?
the lungs are above their resting volume and the chest is below its resting volume thus Pl= 5cmH20 and Pcw= -5cmH20
what happens to the lungs and chest walll in pneumothroax?
lungs collapse to its resting position below RV and the chest wall expands towards its resting position
at rest what are the lungs are and what is the Ppl pressure?
lungs are at FRC and Ppl is negative
what happens to Ppl during inspiration?
becomes more negative due to the expansion of the lungs
how can air flow into the lungs during inspiration? (pressures)
Palv< Patm (negative gradiant)
how can air flow out of the lungs during expiration? (pressures)
Palv > Patm
what happens to the gas in the lungs as the lung volume increases?
gas will decompress
what happens to alveaolr pressure as the lung volume increaseS?
pressure drops
what happens to the pressure gradiant and airflow as the lungs fill up during inspiration?
both gradually decrease
what stops air flow in inspiration
Palv=Patm
what causes to compress the lungs during expiration?
the elastic recoil of the respiratory system
what happens to Ppl as the lung volume decreases during inspiration?
returns to resting levels
at the end of expiration what is the air flow, Palv, and Ppl?
air flow= 0
Palv=0 cm H20
Ppl= -5 cmH20
what does the time course of changes in pleural pressures during inspiration depend on?
diaphragm and air way resistance
what must be the Pressure at the airway opening in order for air to flow into the airways?
must be different then Palv
what is the resitance of the airways to gas flow a ratio of?
pressure difference between alveolar and airway opening over the flow
what can be carried through a large diameter airway?
large flow
is the resistance greater in a large or small diameter airway
resistance is greater in smaller airways
what happens to airway resistance in cases of asthma?
resistances becomes vert high
what happens to pleural and airway pressures during inspiration
they drop
what is the airway pressure at the end of inspiration?
0
what is the airway transmural pressure at the end of inspiration?
8 cm h20
what happens to intrapleural and alveolar pressures during forced inspirations?
pressures increase
what happens to the maximim flow rate and volume exhaled in lungs with restrictive diseases?
reduced
what is the surface tension in the lining of the lungs an important contributior to?
to the mechanical properties of the respiratory system
how do the molecules in the surface arrange themselves?
in their lowest energy conformation, thus more attracted to themselves than to air
what happens to the tension on a curved surface?
it produces a pressure
what equation can be used to approximate the pressure inside the alevoli (small bubble)
P=4T/R
is the pressure greater inside a small or large bubble?
small
what happens if a smaller bubble in the proximity of a larger bubble generates a greater pressure?
the large bubble will blow up
what prevents alveolar collapse?
pulmonary surfactant
what secretes pulmonary surfactant?
type 2 alveolar cells
what are the 2 mian roles of pulmonary surfactant
- making surface tension inside alveoli change with the lung volume
- reduing overall tension allowing to breathe
what is particular propertie about pulmonary surfactant?
decrease surface tension to a greater extend in smaller alveolis
what would happen if surface tension inside lining of the lungs was equal to water?
lungs would not inflate
what happens to tidal volume and breathing frequency when starting to exercise?
both increase proportionally
what are high ventillatory rates during exercise due to?
increase fo frequency due to pleateauing of tidal volume
which is more affected by increased breathing frequency inspiration or expiration?
expiration
what happens to minute ventilation after we pass ~50-65%VO2MAX
minute ventilation increases at a rate disproportionately greater than the ventillatory inflection point
how much can Ve increase during exercise?
35x based on resting volume (5L/min)
how much can the CO increase during exercise in a fit individual?
5-6 x
during exercise what type of response is there in the medullary ecf?
ALKALOTIC (increase pH)
What is caused by the alkalotic response?
decrease of the ventilatory response
when is the role of chemoreceptors most important? at rest or during exercise?
rest
what happen to PaO2 and PaCO2 during exercise?
PaO2 stays constant
PaCO2 will decrease
what happens to ventialtion origin if PaCO2 decreases?
increase in ventilation cannot come from the stimulation of peripheral chemoreceptors by CO2
what happens to arterial Ph during exercise?
it decreases
what is the effect of muscle spindles, golgi tendons and skeletal joint receptors on Ve?
small effect during exercise
does Ve increase before exercise begain?
yes via neural control
what type of control is believed to be responsible for the ventilatory response during the exercise events?
humoral control
