Physiology Flashcards
d:internal respiration
refers to the intracellular mechanisms which consumes O2 and produces CO2
d: external respiration
respiration refers to the sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body
Name the 4 steps of external respiration
Ventilation
exchange of O2 and CO2
Transport of O2 and CO2
Exchange of O2 and CO2 between the blood and the tissues
Name the 4 body systems involved in external respiration
respiratory
cardiovascular
haematology
Nervous
d: Ventilation
mechanical process of moving air between the atmosphere and the alveolar sacs
d: Boyle’s Law
at a constant temperature the pressure of a gas is inversely proportional to the volume of that gas
What way does air flow?
down a pressure gradient (high to low)
The intra-alveolar pressure be _____ than atmospheric for air to flow.
less
How is intra-alveolar pressure reduced in inhalation?
before inspiration, the intra-alveolar pressure=atmospheric
thorax and lungs expand as inspiratory muscles contract
Name the 2 forces that hold the thoracic wall and the lungs in close opposition
- Intrapleural fluid cohesiveness
2. negative intrapleural pressure
How do the pleural membranes stick together?
the h2o molecules in the intrapleural fluid are attracted to each other and resist being pulled apart
What creates the Transmural pressure gradient?
the sub-atmospheric intrapleural pressure creats gradient across both lung and chest wall.
Lungs are forced to expand outwards while the chest is forced to squeeze inwards
What is the transpulmonary pressure?
Transmural pressure gradient across lung wall
What is atmospheric pressure normally?
760mmHg
101kPa
Name the 3 important pressures in Ventilation
Atmospheric
Intra-alveolar
Intrapleural
Is inspiration an active or passive process?
active
Name the main nerve and the 3 smaller ones which are responsible for inspiration muscle contractions?
Phrenic nerve
cervical 3,4,5
What is the major inspiratory muscle?
diaphragm
Describe the movement of inspiration in detail
volume of the thorax increased vertically by contraction of the diaphragm
flattening out dome shape
the external intercostal muscle contracts and lifts ribs and moves out the sternum
What is a consequence of pneumothorax?
abolishes transmural pressure gradient needed for lung expansion.
d: pneumothorax
collapsed lung
Is expiration at rest an active or passive process?
passive
What does the lung recoil do?
makes the intra-alveolar pressure rise
What is the movement of the muscles that causes expiration?
relaxation
Describe muscles before inspiration
external intercostal muscles relaxed diaphragm relaxed (domed)
Describe muscles during inhalation
intercostal muscles contract
rib cage expands
diaphragm contracts moves down
Describe muscles during exhalation
rib cage gets smaller as rib muscles relax
diaphragm relaxes and moves up
What happens to intra-alveolar pressure on inspiration?
decreases below atmospheric
What happens to intra-alveolar pressure on expiration?
increases above atmospheric
What happens to intrapleural pressure on inspiration?
decreases
What happens to intrapleural pressure on expiration?
increases
Name the symptoms of small pneumothorax
shortness of breath
chest pain
Name the physical signs of pneumothorax
hyperresonant percussion note
absent/decreased breath signs
What causes the lungs to recoil during expiration?
elastic connective tissue in the lungs
alveolar surface tension
d: alveolar surface tension
Attraction between water molecules at liquid air interface
In the alveoli this produces a force which resists the stretching of the lungs
what would happen if the alveoli were lined with water alone?
the surface tension would be too strong sop the alveoli would collapse
f: surfactant
reduces alveolar surface tension
preventing smaller alveoli from collapsing and emptying their air contents into larger alveoli
what size of alveoli have a higher tendency to collapse? what law is this based on?
smaller radius alveoli
Laplace’s law
what is pulmonary surfactant made up of?
complex mixture of lipids, proteins secreted by type 2 alveoli
does surfactant lower surface tension of smaller alveoli more or less than that of large alveoli?
more
name a thing that causes respiratory distress syndrome in the new born
fetal lungs don’t develop until late pregnancy, therefore don’t synthesise surfactant until late pregnancy so premature babies wont have enough pulmonary surfactant
what happens to baby respiratory distress syndrome?
strenuous inspiratory efforts in attempt to overcome the high surface tension and inflate the lungs
name another factor apart from alveolar surface tension that helps keep the alveolus open
alveolar independence
describe alveolar independence
If an alveolus start to collapse the surrounding alveoli are
stretched and then recoil exerting expanding forces in the
collapsing alveolus to open it
name the 3 forces keeping the alveoli open
transmural pressure gradient
pulmonary surfactant
alveolar interdependence
name the 2 forces promoting alveolar collapse
elasticity of stretched lung connective tissue
alveolar surface tension
name the accessory muscles of forceful inspiration and whether contract or relax
Sternocleidomastoid, scalenus, pectoral
name the muscles of active expiration and whether contract or relax
Abdominal muscles and internal intercostal muscles
Name the muscles that contract and relax every inspiration and passive expiration respectively
diaphragm
external intercostal muscles
What does IC stand for? and avg value in young adult male?
inspiratory capacity
3.5LWhat does IC stand for? and avg value in young adult male?
What does TV stand for? and avg value in young adult male?
Tidal Volume
0.5L
What does IRV stand for? and avg value in young adult male?
Inspiratory Reserve Volume
3.0L
What does VC stand for? and avg value in young adult male?
Vital Capacity
4.5L
What does ERV stand for? and avg value in young adult male?
Expiratory Reserve Volume
1.0L
What does FRC stand for? and avg value in young adult male?
Functional Residual Capacity
2.2L
What does RV stand for? and avg value in young adult male?
Residual Volume
1.2L
What does TLC stand for? and avg value in young adult male?
Total lung Capacity
5.700L
d: Tidal Volume
Volume of air entering or leaving lungs during a single breath
d: Inspiratory reserve volume
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
d: Expiratory reserve volume
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
d: residual volume
Minimum volume of air remaining in the lungs even after a maximal expiration
d: inspiratory capacity and equation
Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)
d: functional residual capacity
Volume of air in lungs at end of normal passive expiration
(FRC = ERV + RV)
d: Vital Capacity
Maximum volume of air that can be moved out during a single breath following a maximal inspiration
(VC = IRV + TV + ERV)
d: Total Lung Capacity
Total volume of air the lungs can hold
TLC = VC + RV
What respiratory volume cannot be measure by spirometry?
residual
Why is it not possible to measure Total Lung Volume by spirometry?
as residual cannot be measured by it, still air in lungs
what happens to residual volume of thee lungs in emphysema?
increases when the elastic recoil of the lungs is lost
Name the 3 things a volume time curve can tell you
Forced Vital Capacity (FVC)
FEV1 = Forced Expiratory volume in one second
FEV1/FVC ratio
What are dynamic lung volumes useful for diagnosis?
obstructive and restrictive lung disease
d: forced vital capacity
maximum volume that can be forcibly
Expelled from the lungs following a maximum inspiration
d: forced expiratory volume in 1 second
Volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination.
d:FEV1/FVC ratio
The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) X 100%
What is the FEV1/FVC ratio more than?
70%
what is the equation for airway resistance?
flow=change in pressure/resistance
Why does air move with a small pressure gradient?
resistance to flow in airway is normally very low
what is the primary determinant of airway resistance?
radius of the conducting airway
what stimulation causes bronchoconstriction?
parasympathetic
what stimulation causes bronchodilatation?
sympathetic
what 2 diseases cause significant resistance to air flow?
COPD
Asthma
which is more difficult with increased resistance, inspiration or expiration?
expiration
What happens to airways on inspiration? what happens to the intrapleural pressure?
airways are pulled open by the expanding thorax
falls
what happens during expiration to airways and intrapleural pressure?
chest recoils, airways back to og
rises
d: dynamic airway compression
when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways.
What happens in dynamic airway compression?
Pressure applied to alveolus helps
pushes air out of lungs
The rising pleural pressure during active expiration compresses the alveoli and airway
Pressure applied to airway is not desirable - tends to compress it
makes active expiration to be more difficult in patients with airway obstruction
what does increased airway resistance causing an increase in airway pressure help? upstream
open the airways by increasing the driving pressure between the alveolus and airway
What does an obstruction in the airway do to the dynamic airway compression?
the driving pressure between the alveolus and airway is lost over the obstructed segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration
more likely to collapse
what does a peak flow meter do?
gives estimate peak flow rate, assessing airway function
d; pulmonary compliance
Compliance is measure of effort that has to go into stretching or distending the lungs
or
Volume change per unit of pressure change across the lungs
what happens when lungs are less compliant?
the more work is required to produce a given degree of inflation
name some factors which decrease pulmonary compliance
pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant
what does decreased pulmonary compliance mean for patient?
means greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer). This causes shortness of breath especially on exertion
What does decreased pulmonary compliance mean in a spirometer?
may cause a restrictive pattern of lung volumes
When may compliance become abnormally increased?
elastic recoil of the lungs is lost eg. emphysema
What % of total energy expenditure is required for quiet breathing?
3%
How full do lungs normally work at?
half full
name the 4 situations when the work of breathing is increased?
When pulmonary compliance is decreased
When airway resistance is increased
When elastic recoil is decreased
When there is a need for increased ventilation
what is anatomical dead space?
where some of the inspired air remains in airways, not available for gas exchange
What is pulmonary ventilation equal to?
tidal volume X respiratory rate
why is alveolar ventilation less than pulmonary ventilation?
presence of dead space
equation for alveolar ventilation?
(tidal volume – dead space volume) x Respiratory Rate
d: pulmonary ventilation
Is the volume of air breathed in and out per minute
d: alveolar ventilation
Is the volume of air exchanged between the atmosphere and alveoli per minute
Which ventilation represents the new air available for gas exchange with blood?
alveolar
How is pulmonary ventilation increased and why is this more advantageous?
INCREASED depth of breathing (TV) and
rate of breathing (RR)
because of dead space
what two things does the transfer of gases between the body depend on?
ventilation
perfusion
d: ventilation
the rate at which gas is passing through the lungs.
d: perfusion
the rate at which blood is passing through the lungs
why are the avg arterial and alveolar partial pressures of O2 not exactly the same?
Both blood flow and ventilation vary from bottom to top of the lung
what are Ventilated alveoli which are not adequately perfused with blood are considered as?
alveolar dead space
what is the physiological dead space equal to?
the anatomical dead space + the alveolar dead space
what would happen to the alveolar dead space in disease?
increase significantly
What matches airflow to blood flow?
Local controls act on the smooth muscles of airways and arterioles
What does the accumulation of CO2 n alveoli as a result of increased perfusion do?
decreases airway resistance leading to increased airflow
What causes pulmonary vasodilation, which increases blood flow to match larger airflow?
increasing alveolar O2 conc. as a result of increased ventilation
Describe what happens in an area in which perfusion (rate of blood flow) is greater than ventilation (rate of airflow)
C02 increases in area O2 decreases dilation of local airways constriction of local blood vessels airflow increase BF decreases
Describe what happens in an Area in which ventilation (rate of airflow) is greater than perfusion (rate of blood flow)
CO2 decreases in the area O2 increases in the area Constriction of local airways dilation of local BV airflow decrease BF increase
Name the 4 factors that influence the rate of gas exchange across the alveolar membrane
Partial Pressure Gradient of O2 and CO2
Diffusion coefficient for O2 and CO2
Surface area of alveolar membrane
Thickness of alveolar membrane
d: partial pressure of gas
the pressure that a gas in a mixture of gases would exert if it occupied the same volume as the mixture at a certain temperature
What is Dalton’s Law
The Total Pressure exerted by
a gaseous mixture =
The sum of the partial pressures of
each individual component in
the gas mixture
how do gases move across cell membranes?
via pressure gradient
what determines the pressure gradient for a gas?
partial pressure
Give the alveolar gas equation
PAO2(partial pressure of oxygen in the alveolar air)= PiO2(partial pressure of inspired air) -[PaCO2(partial pressure of CO2 in arterial Blood)/0.8]
What is the 0.8 in the alveolar gas equation?
Respiratory Exchange Ratio (RER)
i.e. ratio of CO2 produced/O2 consumed
What is the air in the respiratory tract saturated with? How much does this contribute to the total pressure of the lungs?
water
47mmHg
Why is the partial pressure gradient for CO2 smaller than O2?
CO2 more soluble in membranes than O2
d: the diffusion coefficient
The solubility of gas in membranes
What would a BIG gradient between PAO2 and PaO2(arterial) indicate? Why?
problems with gas exchange in the lungs or a right to left shunt in the heart
as normally its a small gradient
d: Fick’s Law of Diffusion
The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness
Give adaptions lungs that increase gas exchange
LSA in THIN membranes airway divides repeatedly to increase SA alveoli extensive capillary network pulmonary circulation receives the ENTIRE cardiac output
describe composition of alveoli
thin-walled inflatable sacs
1 layer of flattened type I alveolar cells
where are pulmonary capillaries found?
encircling each alveolus
Name some non-respiratory functions of the respiratory system
route for water loss and heat elimination
enhances venous return
maintains normal acid-base balance
speech, singing etc
defends against inhaled foreign matter
nose organ of smell
removes, modifies, activates or inactivates various materials passing through pulmonary circulation
What happens to the O2 picked up by the blood at the lungs?
must be transported in the blood to the tissues for cellular use
What happens to the CO2 produced at the tissues?
must be transported in the blood to the lungs for removal from the body
d: Henry’s Law
The amount of a given gas dissolve in a given type and volume of liquid (e.g. blood) at a constant temperature is: proportional to the partial pressure of the gas in equilibrium with the liquid
How is most O2 in the blood transported?
vis binding to haemoglobin in the red blood cells
What is the percentage of O2 carried bound to haemoglobin?
98.5%
What is the percentage of O2 carried in the dissolved form? and how much is this in litres?
1.5%
3ml per L at PO2 of 13.3kPa
Name the 2 forms O2 is present in the blood with
bound to haemoglobin
physically dissolved
haemoglobin combined with O2 is a reversible/irreversible combination?
reversible
How many haem groups are there in a haemoglobin molecule?
4
how many O2 groups can bind to each HAEM GROUP?
1
When is Hb fully saturated?
when all the Hb present is carrying its maximum O2 load
What is the primary factor which determines the % saturation of haemoglobin with O2?
Po2
What Cation does O2 molecule bind to in Hb?
Fe2+
What shape is the Oxygen Haemoglobin Dissociation Curve and why?
sigmoidal it plateaus because all sites are becoming occupied
d: Oxygen Delivery Index
a function of oxygen content of arterial blood and the cardiac output
What does CaO2 stand for? units
Oxygen content of arterial blood (ml/L)
What does DO2I mean? units
Oxygen Delivery Index (ml/min/metre2)
what is the O2 content of arterial blood is determined by?
the haemoglobin concentration [Hb] and the saturation of Hb with O2
How much O2 can 1 gram of Hb, when fully saturated, carry?
1.34ml
Name 3 disease areas that can impair oxygen delivery to the tissues
respiratory disease
heart failure
anaemia
name 2 things the partial pressure of inspired O2 depends on
total pressure (e.g. atmospheric pressure) and proportion of oxygen in gas mixture (about 21% in atmosphere)
What factor do you multiply kPa by to get it in mmHg?
7.5
How do respiratory diseases impair O2 delivery to tissues?
Decreased partial pressure of inspired oxygen
These can decrease arterial PO2 and hence decrease
Hb saturation with O2 and O2 content of the blood
How does anaemia impair O2 delivery to tissues?
This decreases Hb concentration and hence decreases
O2 content of the blood
How does Heart failure impair O2 delivery to tissues?
decreases cardiac output
What increases the affinity of Hb for O2?
Binding of one O2 to Hb
What is the significance of the flat upper portions of the sigmoid curve, for a change in alveolar Po2?
that moderate fall in alveolar PO2 will not much affect oxygen loading
What is the significance of the steeper lower part of the sigmoid curve, for a change in alveolar Po2?
means that the peripheral tissues get a lot of oxygen for a small drop in capillary PO2
What is the Bohr effect and what change does this induce on the sigmoid curve?
release of O2 by conditions of the tissue (e.g. ^CO2, ^H+, ^temp) leads to shift of the curve to the right, This means more oxygen is released.
Name 4 conditions that increase release of O2
increase in: Pco2 [h+] temp 2,3-Biphosphoglycerate
Which has greater affinity for O2 binding, foetal/adult Hb? Why?
HbF has 2 alpha and 2 gamma units
also interacts less with 2,3- Biphosphoglycerate in red blood cells, hence higher affinity
Is the HbF O2-Hb dissociation curve shifted to the left or right of HbA?
left
What does the high O2 affinity for allow HbF to do for foetus?
This would allow O2 to transfer from mother to foetus even if the PO2 is low
What muscles is Myoglobin present in?
skeletal
cardiac
How many haem groups in myoglobin?
1
What shape of curve is the dissociation curve? Why?
hyperbolic
no cooperative binding of O2
Myoglobin releases O2 at low/high PO2?
low
f: myoglobin
Provides a short-term storage of O2 for anaerobic conditions
what does the presence of myoglobin in blood indicate?
muscle damage
Name the 3 ways CO2 is transported in the blood and %
solution 10%
bicarbonate 60%
carbamino compounds 30%
How is bicarbonate formed and where?
In this system, carbon dioxide diffuses into the red blood cells
Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions
(HCO3)
(HCO3−)
and hydrogen (H+) ions
d: Haldane effect
removing O2 from Hb increases ability of Hb to pick up CO2 and CO2 generated H+
Why is CO2 carried in solution
20x more soluble than 02
what is equation for bicarbonate formation?
CO2 + H2O H2CO3 H+ +HCO3-
How are carbamino compounds formed?
Carbamino compounds formed by combination of CO2 with terminal amine groups in blood proteins.
Especially globin of haemoglobin to give carbamino-haemoglobin
Why can reduced Hb bind more CO2 than Hb02?
O2 has be lost therefore more room
How do Boher and Haldane effect work in synchrony?
O2 liberation and uptake of CO2 & CO2 generated H+ at tissues
Explain the boher-haldane effect at the lungs;
At the lungs the Hb pick-up the O2
This weaken its ability to bind CO2 and H+
what is the major rhythm generator in respiring and why?
medulla
ventilation ceases below medulla section of brain and remains fairly normal above the medulla
what is the normal rhythm of respiration?
inspiration followed by expiration
what network of neurones generates breathing rhythm? Where are they located?
pre-botzinger complex
upper end of the medullary respiratory centre
describe the neural process that gives rise to inspiration
Rhythm generated by Pre-Botzinger complex
Excites Dorsal respiratory group neurones (inspiratory)
Fire in bursts
Firing leads to contraction of inspiratory muscles - inspiration
what happens when firing of dorsal neurones stops?
passive expiration
describe what happens neurally during active expiration during hyperventilation?
Increased firing of dorsal neurones excites a second group:
Ventral respiratory group neurones
Excite internal intercostals, abdominals etc leads to forceful expiration
What do the ventral neurones NOT do in quiet breathing?
activate expiratory muscles
By what can the rhythm generated in the medulla be modified by?
the neurones in the pons
describe the process by with the rhythm generated in the medulla be modified by the neurones in the pons
Pneumotaxic Centre” (PC)
Stimulation terminates inspiration
PC stimulated when dorsal respiratory neurones fire
Inspiration inhibited
what would happen without the PC?
breathing is prolonged inspiratory gasps with brief expiration - APNEUSIS
d: apneusis
is an abnormal pattern of breathing characterized by deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release.
f: apneustic centre
Impulses from these neurones excite inspiratory area of medulla
Prolong inspiration
Name the 7 receptors that influence respiratory centres
Higher brain centres e.g. cerebral cortex, limbic system, hypothalamus
Stretch receptors in the walls of bronchi and bronchioles
Juxtapulmonary (J) receptors
joint receptors
baroreceptors
central chemoreceptors
peripheral chemoreceptors
what are juxtapulmonary receptors stimulated by?
pulmonary capillary congestion and pulmonary oedema (caused by e.g. left heart failure)
what is a characteristic symptom of pulmonary embolism?
rapid shallow breathing
name 4 examples of involuntary modifications of breathing
pulmonary stretch receptors eg hering-breuer reflex
joint receptors in exercise
stimulation of respiratory centre in temperature, adrenaline, or impulses from cerebral cortex
cough reflex
describe how pulmonary stretch receptors become activated during inspiration and eg
afferent discharge inhibits inspiration Hering- Breuer reflex
do pulmonary stretch receptors switch off during normal respiratory cycle?
unlikely, only activated at large greater than 1L tidal volumes
how do joint receptors increase breathing and what else do they do?
Impulses from moving limbs reflexly increase breathing
Probably contribute to the increased ventilation during exercise
Name the factors that may increase ventilation during exercise
reflexes from body movt adrenaline release impulses from the cerebral cortex increase in body temp later on: accumulation of CO2 and H+ generated by active muscles
what does cough reflex do to modify breathing?
where is its control mechanism?
vital part of body defence mechanisms
clears airway of dust
medulla
describe the mechanism of a cough?
Afferent discharge stimulates: short intake of breath, followed by closure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsion of air at a high speed
what is an example of negative feedback control in respiration? what are the controlled variables in this and what senses these?
chemical control of respiration
controlled variables are the blood gas tensions, especially carbon dioxide
Chemoreceptors
f: peripheral chemoreceptors and egs
Sense tension of oxygen and carbon dioxide;
and [H+] in the blood
carotid and aortic bodies
where are central chemoreceptors found?
near the surface of the medulla
f: central chemoreceptors
Respond to the [H+] of the cerebrospinal fluid (CSF)
how is CSF seperated to blood and what happens at it?
blood-brain barrier
Relatively impermeable to H+ and HCO3-
CO2 diffuses readily
why is CSF less buffered than blood?
contains less protein than blood
d: hypercapnia
excessive carbon dioxide in the bloodstream, typically caused by inadequate respiration
how is hypercapnia generated?
central chemoreceptors
d: hypoxia
inadequate oxygen supply at tissue level
what receptors are stimulated during hypoxia?
peripheral chemoreceptors
at what partial o2 pressure are peripheral chemoreceptors stimulated?
lower than 8kPa
when is hypoxic drive most prevalent in patients?
in patients with chronic CO2 retention (e.g. patients with COPD)
at high altitudes
how is hypoxia at high altitudes caused?
Decreased partial
pressure of inspired
Oxygen (PiO2)
what is the body’s acute response to high altitude induced hypoxia?
hyperventilation and increased cardiac output
what are the symptoms of acute mountain sickness?
headache, fatigue, nausea, tachycardia, dizziness, sleep disturbance, exhaustion, shortness of breath, unconsciousness
name the chronic adaptions to high altitude hypoxia
increased RBC production increased 2,3 BPG produced within RBC increased number of capillaries increased number of mitochondria kidneys conserve acid making the arterial pH less
true/false
H+ readily crosses the blood brain barrier
false
what receptors adjust acidosis?
peripheral chemoreceptors play a major role in adjusting for acidosis caused by the addition of non-carbonic acid H+ to the blood
how do peripheral chemoreceptors affect acidosis?
Their stimulation by H+ causes hyperventilation and increases elimination of CO2 from the body (remember CO2 can generate H+, so its increased elimination help reduce the load of H+ in the body)
what effect does severe hypoxia have on the respiratory centre?
depresses it
