Respiratory System Flashcards
To stay awake
What are some common respiratory conditions?
Asthma Emphysema Cystic Fibrosis Chronic Bronchitis COPD (Chronic obstructive pulmonary disease)
What are the main functions of the respiratory system?
Gas exchange (atmosphere + blood) (blood + tissue) Regulation of body pH (CO2 release) Vocalisation Protection Synthesis of hormones
What forms the upper respiratory tract?
Nasal Cavity
Pharynx
Vocal Cord
Larynx
What is the function of the upper respiratory tract?
Warm
Humidify
Filter
Vocalise
What is asthma?
Respiratory condition caused by inflammation and spasms of the bronchioles. Usually triggered due to hypersensitivity.
What is emphysema?
Air sacs of the lungs are damaged and enlarged. Common in smoking and causes breathlessness
What is cystic fibrosis?
Production of thick mucus which leads to the blockade of bronchi, often results in respiratory infection.
What forms the lower respiratory tract?
Trachea
Bronchi
Bronchioles
Alveoli
What are the functions of the lower respiratory tract?
Conduct Air
Stabilise conductive airways
Regulate flow
Gas Exchange
What keeps the trachea open?
U-shaped cartilage rings and the trachealis muscle.
What important reflex does the trachealis muscle facilitate?
Coughing
What keeps the bronchi open?
Cartilage Rings (Upper) Plates (Lower Parts)
What is the function of goblet cells?
Secrete mucus to coat the respiratory tract
What is the function of ciliated cells?
Sweep mucus upwards to the pharynx, to be swallowed
What is the combined function of goblet and ciliated cells called?
The mucociliary escalator
What is the structure of Bronchioles?
Small diameter
Smooth muscle walls
How are bronchioles diameter regulated?
Histamines constrict bronchioles Parasympathetic NS (Acetylcholine induce bronchoconstriction) Sympathetic NS (Noradrenaline induces bronchodilation)
What is the structure of Alveoli?
Single cell width
Side facing capillaries - ‘leaky’ for gas exchange
Supporting side - Elastic fibres (collagen IV) , robust
What blood vessels supply the respiratory zone
Pulmonary Artery (deoxygenated blood) Capillary Network (Increases gas exchange) Pulmonary Vein (oxygenated blood)
What is the respiratory zone?
Consists of the ends of the bronchioles, alveoli and the vessels that support them.
How many types of Alveolar cells are there?
2-
Cell Type I (gas exchange)
Cell Type II (Production of surfactant)
What does surfactant do?
Reduces surface tension and prevents alveoli from collapsing
What are the pores of Kohn?
They allow for intra-alveolar ventilation
What do macrophages do related to the alveoli?
They protect from small particles and ingest degraded surfactant
Which part of the respiratory tract has the highest resistance?
The bronchi
What does flow rate ely on?
Viscosity of the gas
Airway resistance
Flow pattern (turbulence)
What conditions can increase resistance?
Inflamed airways,
Increased mucus secretion
What is a ‘shunt’?
When blood from the bronchiolar artery draining into pulmonary circulation.
What membrane lines the thoracic wall?
The parietal pleura
What membrane lines the surface of the lungs?
Visceral Pleura
Why is intrapleural pressure less than atmospheric cavity?
As the lungs and chest wall are pulling away from each other.
What is boyle’s law?
If volume increases, pressure will decrease
P1 x V1 = P2 x V2
How does standing upright help breathing?
Gravity facilitates the diaphragm lowering.
What is lung compliance?
How easily the lung can be inflated and emptied
How do you calculate compliance?
Change in volume/change in pressure
What affects lung compliance?
The elasticity of the lung
Surface tension in the alveoli
How is lung compliance limited?
As the college fibres have limited length
What is the law of LaPlace?
P =2T/r
What does a spirometer do ?
monitors the volume of air inspired and expired usually done under quiet breathing and no time restraitnts
What is a lung volume ?
A single difference
What is a lung capacity ?
the sum of 2 or more lung volumes
What is tidal volume ?
volume of air that moves during a single inspiration or expiration (500 ml)
What is inspiratory reserve volume ?
Additional air you inspire on top of tidal volume
What is expiratory reserve volume ?
Amount of air forcefully exhaled at the end of normal expiration
What is residual volume ?
the volume of air remaining in the respiratory system after maximum exhalation
What is vital capacity ?
inspiratory reserve volume + expiratory reserve volume + tidal volume
What is total lung capacity ?
vital capacity + residual volume
What is functional residual capacity ?
Expiratory reserve volume + residual volume
What are dynamic measurements ?
they assess the time taken to exhale a certain volume of air
What is FEV ?
forced expired volume
How fast air leaves the airways in 1 second
What is FVC ?
Forced vital capacity
the defined amount of air that can be forcibly exhaled from the lungs after taking the deepest breath possible
What are the characteristics of restrictive lung disease ?
FVC reduced
FEV close to normal
What are the characteristics of obstructive lung disease ?
FEV reduced
FVC close to normal
What is a pneumothorax?
Presence of air in the cavity between the lung and the thoracic cavity.
What factors affect gas exchange?
Sufrace area
Thickness of the membrane
Concentration gradient
Solubility of the gas
What is meant by the term dead space?
Airways that are ventilated but not designed for gas exchange (perfusion)
What is the consequence of dead space on alveolar air?
When breathing in ‘used’ air, remaining from previous expiration, re-enters the alveolar space and ‘dilutes’ the fresh air.
What does the fowlers method measure?
Anatomic dead space
What does dalton’s law state?
The total pressure of a gas mixture is equal to the sum of partial pressures of the individual gases
How do you calculate diffusion capacity?
Rate of gas transfer from lung to blood/ driving partial pressure
How does emphysema affect gas exchange?
Destruction of alveoli means less surface area for gas exchange
How does asthma affect gas exchange?
Increased airway resistance decreases airway ventilation
How does pulmonary oedema affect gas exchange?
Fluid in interstitial space increases diffusion distance.
What are the boundaries of the thorax ?
posteriorly - thoracic vertebrae
laterally-ribs
anteriorly - sternum
How many thoracic vertebrae are there ?
12
What are the features of a typical thoracic verebra ?
body-heart shaped
spinous process-long and slender
articular process - on the body for the rib above
costovertebral facets - these are the superior and inferior demi facets
costotransverse facets - facets on the transverse processes
What are the features of a rib ?
head- facets for articulation with the demi facets in the vertebra
neck - enlarged bit is the crest
Tubercle - between the neck and the body - articulates with the facets on the transverse processes
Costal groove - on the internal inferior surface in which the neurovascular bundle runs
pit - joins to the costal cartilages
What are the 3 parts of the sternum ?
the manubrium , body and the xiphoid process
What are the 3 notches on the manubrium of the sternum ?
sternal notch
clavicular notch
notches for the costal cartilages of the first rib
What is the structure between the manubrium and the body of the sternum ?
the angle of louis or the sternal angle
What type of joint is the angle of louis ?
Symphysis
What structures bind the thoracic inlet ?
body of the first thoracic vertebra
1st rib
manubrium of the sternum
roofed by pleura
What does the thoracic inlet transmit ?
trachea oesophagus carotid artery subclavian arteries internal jugular veins brachial veins vagus nerve phrenic nerve
What are the boundaries of the thoracic outlet ?
body of the 12th vertebra
lower ribs
xiphoid cartilage
closed by the diaphragm
What does the thoracic outlet transmit ?
oesophagus dorsal aorta inferior vena cava vagus nerve phrenic nerve
What are costovertebral joints ?
articulations between the facets on the head of the rib and the facts on demi facets on the vertebra
What type of joints are the costovertebral joints ?
synovial - depression and elevation
What are the costotransverse joints ?
articulations between the facets on the transverse processes and the tubercle of the rib
What are costochondral joints ?
joints between the costal cartilages and the distal ends of the ribs
synchondroses
What are chondrosternal joints ?
between costal cartilages and the sternum
What are interchondral joints ?
between the costal cartilges
What is the type of joint between the manubrium and the first rib ?
Synchondrosis
What type of action do ribs perform ?
lever action
What happens to the ribs in ventilation ?
they elevate causing an increase in thoracic dimensions
How do the a-p and transverse diameters increase ?
anterior rib ends rise and protrude more
What are the precise movements of ribs 3 and 6 ?
elevation occurs by rotation at the neck - increasing a-p dimensions
What are the precise movements of ribs 7 and 10 ?
elevation occurs by sliding outwards and backwards increasing transverse dimensions
What are the intercostal muscles ?
the external
the internal
the innermost
What do the external intercostal muscles do ?
pass from rib to rib in an anteroinferior direction
they elevate the ribs in inspiration
What do the internal intercostal muscles do ?
pass from rib rib in perpendicular to the external intercostal muscles - they depress the ribs in inspiration
What do the innermost intercostal muscles do ?
the internal and the innermost muscles are separated by the neurovascualr bundles - intercostal arteries , nerves and veins - VAN
What is the thoracic cavity divided into ?
the right and left pleural cavities
the mediastinum
What do the pleural cavities contain and what are they lined with ?
they contain the lungs and are lined with pleura
What are the 2 types iof pleura ?
parietal
visceral
What is the parietal pleura ?
covers the inner aspect of the pleural cavity
What is the visceral pleura ?
covers the lungs
What is between the parietal and the visceral pleura ?
the pleural cavity - contains the pleural fluid
What is the costodiaphragmatic recess ?
a space between the lungs and the diaphragm created by the pleura
What are the fissures in the left lung ?
the oblique fissure creates the upper and lower lobes
What are the fissures of the right lung ?
the horizontal and the oblique fissures create the upper middle lower lobes
What is the depression found in the left lung ?
the cardiac notch to contain the heart
What is on the mediastinal aspect of each lung ?
the hilum of the lung - entrance for blood vessels and the tubes
What are the structures found in the hilum ?
primary bronchus
2 pulmonary veins
pulmonary artery
bronchial arteries - associated with the primary bronchus
What are the differences between the right and left primary bronchi ?
the right primary bronchus is wider and more vertical - more likely to find foreign bodies lodged in here
What are the 4 surfaces of the heart ?
apex
diaphragmatic surface
costal surface
mediastinal surface
Where can you find the intercostal NV bundle ?
running in the costal grooves of the ribs
Where does the intercostal nerve arise from ?
primary ramus of a thoracic spinal nerve
What are the branches of the descending aorta in the thorax ?
the posterior intercostal arteries and paired pericardial, oesophageal and bronchial arteries.
What is a bronchopulmonary segment ?
a segment of lung tissue with its own bronchus and blood supply which acts independent of other segments - can be removed without causing damage
Which branches of the subclavian artery provide an arterial supply to the thorax ?
internal thoracic artery and the costocervical trunk
What type of joints are formed between the head of the rib and the demifacets ?
synovial
How does the head of the rib articulate with the vertebra ?
the head of the rib articualtes with the same thoracic vertebra and the one above - form a full circle from the demi facets
What do ribs 11 and 12 lack ?
a transverse facet
What do the intercostal nerves supply ?
they supply the intercostal muscles and the skin supplying the space between the ribs
What is the origin of the sympathetic fibres found in the intercostal nerves ?
the ganglia of the sympathetic chain
Where do the fleshy fibres of the diaphragm insert ?
into the central tendon
What is the morphology of te diaphragm ?
double domed
What type of muscle is the diaphragm ?
skeletal muscle
What are the 2 recesses assocaited with the diaphragm ?
costomediastinal reccess
costodiaphragmatic reccess
Where is the costodiaphragmatic recess ?
within the lung
Where is the costomediastinal recess ?
between the parietal pleura and the costal pleura
What are the attachments of the diaphragm ?
sternal
costal
verterbral
lumbocostal arches
What is the sternal attachment of the diaphragm ?
Xiphoid process
What is the costal attachment of the diaphragm ?
lower 6 costal cartilages
What are the vertebral attachments of the diaphragm ?
left and right cruae and lumbocostal arches
What are the right and left crue ?
they are the parts of the diaphragm that arise from the vertebrae
Where does the right crus arise from ?
arises from L1-L3 and some fibres form around the oesophageal opening
Where does the left crus arise from ?
from L1-L2
What are the types of lumbocostal arches ?
median and lateral
What are the 3 diaphragmatic apertures ?
caval
oesophageal
aortic
What is the aortic aperture ?
T12 Passes between the fibres of the 2 crura
What is the oesophageal apertures ?
made from the fibres of the right crura
T10
What is the caval opening ?
the inferior vena cava passes through this opening in the central tendon at T8
What passes through the caval hiatus ?
the inferior vena cava
right phrenic nerve
What passes through the oesophageal hiatus ?
oesophagus
right and left vagus nerves
What passes through the aortic hiatus ?
descending aorta
thoracic duct
azygous vein
sympathetic chains
What is the motor innervation of the diaphragm ??
the anterior ramii of C3-C5 that form the phrenic nerve
What is the sensory innervation of the diaphragm ?
centrally - phrenic nerve
laterally - lower 5 intercostal nerves
What are the functions of the diaphragm ?
ventilation-regulation of thoracic pressure micturition parturition daefacation lifting
What does the anterior abdominal wall consist of ?
1 central vertical muscle which is rectus abdominis
3 flat lateral muscles - internal oblique , external oblique and transversus abdominis
What is the transversalis fascia ?
a layer of fascia found depp to the transversus abdominis
What are the attachments of the rectus abdominis ?
attaches between the ribs and the pubic bone
3 transverse tendinous bands that join to the linea alba
What are the attachments of the external oblique ?
Arises from the lower 8 ribs and inserts into the linea alba , pubic bone , inguinal ligament and iliac crest
runs inferomedially
What are the attachments of the internal oblique ?
Runs superomedially
Arises from below the pelvis and iliac crest and inserts into the costal margin and the linea alba
What are the attachments of the transversus abdominis ?
Arises from the lower 6 ribs and lumbar fascia , iliac crest and the inguinal ligament and inserts into the linea alba
What is the innervation of the muscles of the anterior abdominal wall ?
T7-L1 intercostal nerves which run between internal oblique and transversus abdominis
What are the functions of the muscles of the anterior abdominal wall ?
trunk movements
abdominal pressure regulation
expiration - accessory muscles
How much blood do the lungs receive per minute?
5l/min
How much air do the lungs receive per minute?
5l/min
Why is interpleural pressure less than atmospheric pressure?
Because the lungs and chest wall pull away from each other.
What challenges does the pulmonary circulation face?
The right ventricle can’t generate high pressure.
How does the pulmonary circulation overcome its challenges?
The vascular resistance in the pulmonary circulation is 1/10th that of the systemic circulation.
How can you assess ventilation and perfusion in the lungs?
Insert a radioactive compound into airspaces of the lung and into veins of the lung.
‘Mismatch’ of compounds highlights areas where either ventilation or perfusion is affected.
What does V/Q stand for?
Ventilation/Perfusion ratio.
What can cause a high V?Q?
High alveolar O2 caused by vasodilation
Low alveolar CO2 caused by bronchoconstriction
What is hypoxic pulmonary vasoconstriction (HPV)?
This is when small arteries in the lungs constrict in hypoxic conditions. This redirects blood flow to well ventilated regions increasing V/Q
How is HPV linked to birth?
In utero the lungs aren’t ventilated, therefore after birth when O2 reaches the lungs HPV is lifted and perfusion greatly increases
What is COPD?
Chronic obstructive pulmonary disease
How is HPV linked to COPD?
In COPD ventilation in certain areas are low.
This trigger HPV.
Resistance increases, Pulmonary BP increases which could lead to right ventricular heart failure
What is venous admixture?
When blood passes through the lung without being properly oxygenated
What can cause venous admixture?
Anatomical Shunt - Blood bypasses the lungs through an anatomical channel
Low V/Q - When there is more blood in capillary than can be fully oxygenated (tumours, oedemas)
What are the risk of high levels of oxygen?
High levels may reduce ventilation and cause CO2 retention causing the pH to fall
Relatively little CO2 will enter the alveoli, this ay cause the alveoli to collapse
What is the direction of movement of Rectus Abdominis ?
downwards
What is the direction of movement of transversus abdominis ?
medially
What is the direction of movement of external oblique ?
inferomedially
What is the direction of movement of Internal oblique ?
Superiomedially
What is the solubility of oxygen?
3ml/l
What is the consumption of O2 at rest?
250 ml/min
FUCK THE ITALIANS!!!!
GO ESKIMOS
What is the required cardiac output to match consumption and solubility (without haemoglobin)?
84litres/minute
What would the heart rate be without haemoglobin?
Around 1200 beats/min
With haemoglobin what is the solubility of O2?
200ml/l
What is the over capacity of oxygen transport?
Under normal CO (5l) there is 4x over capacity
What is the structure of adult haemoglobin?
2 alpha subunit
2 beta subunits
4 haem groups
What is the structure of foetal haemoglobin?
2 alpha subunits
2 delta subunits
What % of erythrocyte mass is Hb?
Around 33%
Why do males have higher Hb % than females?
As androgens cause vasoconstriction.
Where does CO2 bind to haemoglobin?
The N-terminus of Hb
Why does the initial binding of 02 to a haem group promote further binding?
It forms an allosteric change in structure which promotes further binding.
What is 2-3 DPG (Diphosphoglycerate)?
Produced in RBC’s, increases offload of oxygen to tissues at low P(O2)
What is important about Foetal Hb?
It has a higher affinity for oxygen than the maternal hb, this means it ‘steals’ oxygen from the mother blood.
What is Anoxia?
Complete deprivation of oxygen
What is hypoxia?
Reduced oxygen supply
What is cyanosis
02 saturated haemoglobin is purple. Reduced saturation causes bluish discolouration of the skin and mucous membranes
What is Hypercapnia?
Increased levels of CO2
How is CO2 spread in the body?
7% is soluble
23% is bound to Hb
70% is found in Bicarbonate
Why is bicarbonate important?
It is an important buffer in the blood
What is the Bohr effect?
Protons reduce Hb’s affinity for O2
What is the haldane effect?
CO2 reduces Hb’s affinity for O2
What are the main goals of the respiratory system ?
ensure alveolar ventilation is sufficient to maintain gas pressure
adapt ventilation to physiological or metabolic need
integrate ventilation with non respiratory activities
What do peripheral chemoreceptors sense ?
mainly oxygen
What are the 2 locations of the peripheral chemoreceptors ?
aortic bodies and the carotid bodies
How much of the response to oxygen to peripheral chemoreceptors mediate ?
100%
How much of the response to carbon dioxide do central chemorecepetors mediate ?
15%
Are peripheral or central chemoreceptors quicker at responding to carbon dioxide ?
peripheral
What potentiates the oxygen response ?
low pH and high co2
Where does the sensory information go ?
respiratory centre in the medulla
How does sensory info from the aortic bodies get to the respiratory centre ?
vagus nerve
How does sensory info get from the carotid bodies to the respiratory centre ?
glossopharyngeal nerve
What are type 1 glomus cells ?
peripheral chemoreceptors located in carotid bodies and aortic bodies
What are type 2 glomus cells involved in ?
support
What are the characteristics of glomus cells ?
well perfused - able to detect changes in oxygen quickly
high metabolic rate - any drops in oxygen are detected
Is there a high intensity of signal transmission when you remove oxygen ?
yes - via the glossopharyngeal nerve
Is there a higher rate of ventilation or lower when co2 increases and pH drops ?
higher - more signla transmission via the glossopharyngeal nerve
How is a low oxygen level detected ?
low oxygen in the blood potassium channels close cell depolarises voltage gated calcium channels open calcium entry exocytosis of dopamine vesicles binding of dopamine receptors signals to medullary centres to increase ventilation via glossopharyngeal
At what pressure of oxygen does ventilation start to become responsive to low O2 ?
60 mmHg
What is the effect of decreasing oxygen as well as carbon dioxide on the ventilatory response ?
potentiates the response - slope become steeper as both stimuli come together to stimulate the ventilatory response
What is the main parameter for the ventilatory response ?
carbon dioxide
What is the blood-brain barrier impermeable to ?
bicarbonate and protons
What easily diffuses across the blood-brain barrier ?
carbon dioxide
What happens to c02 in the cerebral capillaries ?
co2 diffuses across the BBB into the CSF where the reaction with water (catalysed by carbonic anhydrase) turns into carbonic acid and then protons and bicarbonate
What happens to the protons ?
they are detected by the central chemoreceptors
signals sent to respiratory control centre and there is increased ventilation to counter act
Where are the central chemoreceptors located ?
in the venterolateral surface of the medulla and are bathed in CSF
What does an increase in Co2 do to ventilation ?
linear response
At what level of c02 is there no change in ventilation ?
30 mmhg
What happens if oxygen and carbon dioxide levels are both decreased ?
the 2 stimuli potentiate other - oxygen and carbon dioxide have synergic effects
What effect does acidosis have on the ventilation rate ?
there is a higher ventilation rate - steeper slopes representing more sensitivity - the proton and the carbon dioxide response potentiate one another to produce a bigger change in ventilation
What happens during sleep or a narcotic overdose ?
there is a reduced sensitivity to oxygen (right shift)
higher tolerance of co2
What happens in heroin overdose ?
less response to carbon dioxide
forget to breathe
autonomous activity not stimulated enough
What happens in the instance of ‘death in shallow water’ ?
hyperventilation reduces pCO2 (30 mmhg-no response) and a moderate increase in oxygen
the ventilatory drive is reduced and the oxygen deficit is overruled so ventilation decreases - die due to o2 deficit
Where are peripheral chemoreceptors located ?
carotid bodies and aortic arch
What do peripheral chemoreceptors sense ?
pH co2 and O2
What is the relative speed of peripheral chemoreceptors ?
relatively quick
Where are central chemoreceptors located ?
floor of the 4th ventricle bathed in CSF
What do the central chemoreceptors sense ?
c02
`What is the relative speed of central chemoreceptors ?
relatvely slow
What provides the major ventilatory drive for central chemoreceptors ?
carbon dioxide
What are the advantages of using a carbon dioxide based system ?
carbon dioxide production is related to oxygen consumption
Carbon dioxide production is related to pH
Linear relationship - Carbon dioxide changes are buffered by changes in pH
What are the 3 types of receptors related to vagal afferent reflexes ?
slowly adapting pulmonary stretch receptors
rapidly adapting pulmonary receptors (irritant)
J receptors
Where are the stretch receptors located ?
large airways and the visceral pleura
What do the stretch receptors detect ?
stretch detected by thoracic cavity expansion
What is the effect of activating the stretch receptors ?
signals are sent to he respiratory centre when expanded enough to terminate inspiration and limit tidal volume
extedn expiration
What is an exmaple of the use of stretch receptors ?
herring-breuer reflex
Where are peripheral chemoreceptors located ?
carotid bodies and aortic arch
What do peripheral chemoreceptors sense ?
pH co2 and O2
What is the relative speed of peripheral chemoreceptors ?
relatively quick
Where are central chemoreceptors located ?
floor of the 4th ventricle bathed in CSF
What do the central chemoreceptors sense ?
c02
`What is the relative speed of central chemoreceptors ?
relatvely slow
What provides the major ventilatory drive for central chemoreceptors ?
carbon dioxide
What are the advantages of using a carbon dioxide based system ?
carbon dioxide production is related to oxygen consumption
Carbon dioxide production is related to pH
Linear relationship - Carbon dioxide changes are buffered by changes in pH
What are the 3 types of receptors related to vagal afferent reflexes ?
slowly adapting pulmonary stretch receptors
rapidly adapting pulmonary receptors (irritant)
J receptors
Where are the stretch receptors located ?
large airways and the visceral pleura
What do the stretch receptors detect ?
stretch detected by thoracic cavity expansion
What is the effect of activating the stretch receptors ?
signals are sent to he respiratory centre when expanded enough to terminate inspiration and limit tidal volume
extedn expiration
What is an exmaple of the use of stretch receptors ?
herring-breuer reflex
Where are rapidly adapting (irritant) pulmonary receptors found ?
underneath airway epithelium at bifurcations
What do rapidly adapting pulmonary receptors (irritant) detect ?
flow (rate of change)
When are rapidly adapting receptors most active ?
when a person inhales noxious substances
Where are pulmonary C fibre (J receptors) found ?
juxtapulmonary capillaries
When are J receptors triggered ?
when the lung is diseased - pulmonary eedema and the release of histamine
What type of breathing pattern is triggered with the J receptors ?
aponea followed by rapid shallow breathing
What are the 2 neurogenic control systems ?
voluntary and involuntary
Which part of the brain initiates voluntary control ?
cerebral cortex
Where are the signals from the voluntary control system sent ?
respiratory centre in the medulla
What produces the response in the voluntary control system ?
respiratory muscles
Inhibitory and excitatory neurones display what ?
reciprocal innervation - they are mutually inhibitory
The voluntary and involuntary systems are ….
independent of one another and can be overrriden
What do both the voluntary and involuntary systems require ?
descending pathways - alpha motoneurones to the respiratory muscles and descneding pathways
Which muscle system controls the muscles of respiratory ventialtion ?
somatic motor system
What does the Autonomic nervous system control ?
smooth muscle contraction and secretion
Where are the 2 respiratory centres ?
in the pons and the medulla
What is the role of the pons ?
modulation
What is the role of the medulla ?
the medulla is the site of the rhythmic respiratory centre and it generates the automatic breathing pattern
What is the medulla made of ?
2 groups of neurones - the DRG and the VRG
What does the DRG do ?
generates the inspiration firing pattern and hence the inspiratory drive
output via the phrenic nerve activates respiratroy muscles and initiates inspiration
What does the VRG do ?
mainly expiratory neurones (at the ends)
some inspiratory neurones are found in the pre-botzinger complex
What is the pre-botzinger complex ?
found in the VRG centrally
a rhythm generator - cells within it generate the basic rhythm
Destruction of the VRG and the DRG leads to ?
immediate and permanent termination of automatic respiration
During inhalation what is the activity of inspiratory neurones , phrenic nerve and the external intercostal nerves ?
inspiratory neurones fire
phrenic nerve increases activity
external intercostal nerves fire
During exhalation what is the activity of the phrenic , expiratory neurones and internal intercostal neurones ?
expiratory neurones fire
reduced activity of the phrenic and the external intercostal
internal intercostal neurones fire
What is cheyne-stokes respiration ?
deeper and faster breathing followed by apnea
What causes cheyne-stokes respiration ?
over and under correction of pC02 due to increased transit time between the lung and the carotid body
The conducting airways are .. ?
ventilated but not perfused
The conducting airways are known as ?
dead space - no gas exchange takes place
Why does some air enter the respiratory system but not reach the alveoli ?
because part of each breath remains in the airways like the trachea and the bronchi
What is the anatomic dead space ?
the volume of the conducting airways (150 ml)
What is the alveolar dead space ?
the volume of air in the alveoli that is ventilated but not perfused due to V/Q mismatch
What is the physiologic dead space ?
anatomic air space + alveolar dead space
In animals how big is the anatomic dead space ?
1/3 of tidal volume
What happens in the dead space at the end of inspiration ?
the anatomic dead space is filled with fresh air at the end of inspiration (150)
What happens in the dead space during expiration of tidal volume ?
the first exhaled air comes out of the dead space
150 ml comes out the dead space
350 ml is left in the alveoli
What happens to the dead space at the end of expiration ?
it is filled with stale air
If you inhale 500 ml of air what happens ?
the dead space is filled with air (150)so this goes to the alveoli- so only 350 actually reaches the alveoli
How can we measure anatomic dead space ?
using fowlers method
Describe fowlers method ?
one breath of pure oxygen (any gas that doesnt contain nitrogen)
gas that doesnt take place in alveolar gas exchange is exhaled first and the alveoalr air
What does henrys law state ?
the amount of gas dissolved in a liquid is determined by the partial pressure of the gas and its solubility in the liquid
What is the order of solubility of co2 , o2 and n2 ?
CO2 > O2 > N2
Oxygen being poorly soluble is compensated by the fact that ?
it has a large pressure gradient
What compensates for the low c02 pressure gradient ?
the high solubility of carbon dioxide
How is diffusion capacity optimised in the lungs ?
the shape of type 1 alveoalr cells
fused basement membranes
What does diffusion capacity measure ?
the amount of gas travelling from the alveolar dead space to the blood
How do you calculate diffusion capacity ?
rate of gas transfer from lung to blood / driving partial pressure
What does diffusion capacity depend on ?
solubility of the gas
When is Diffusion capacity impaired ?
in respiratory diseases
Which parts of the lung are poorly perfused and why ?
apex due to limited force of contraction of the right ventricle
What does the efficiency of the lung depend on ?
diffusion and perfusion
What happens in a perfusion limited scenario ?
there is not enough blood to carry away thr gas transferred
rapid transfer of gas between the alveolus and the blood
equilibrium is reached before the end of the capillary bed
Which molecules are perfusion limited ?
n20 and 02
What happens in a diffusion limited scenario ?
slow transfer of gas across the blood and alveolus interface
equilibrium is not reached in transit time
The lung receives how much blood from the cardiac output ?
5L / min
How can we measure ventilation using Xe 133 ?
Xe 133 is inhaled and it distributes evenly in the alveolar space
radiograph shows that the apex is fainter showing that it is well ventilated
What is the normal ventilation/perfusion ratio ?
1 (5/5)
At the beginning of inspiration intrapleural pressure is what ?
-3 mmhg
As inspiration proceeds what do the pleural membranes and lungs do ?
they follow the expanding rib cage
Why is intrapleural pressure less than atmospheric pressure ?
because the lungs and chest wall pull away from each other
What effect does gravity have on the alveoli ?
the weight of the lung means that alveoli at the base are compressed whilst alveoli at the top are distended
Where are ventilation and perfusion efficient ?
at the base rather than the apex
What happens at the apex ?
perfusion and ventilation are low
the alveoli are distended so they squeeze the capillaries and ventilation > perfusion
If ventilation is high at the apex what does this mean ?
there is a low amount of co2 and therefore a high pH
What happens at the base of the lung ?
volume is higher
V/Q in favour of perfusion
low hydrostatic pressure to overcome
po2 is lower and pco2 is higher - lower pH
How can we assess ventilation and perfusion ?
Xe 133
How can we measure ventilation using Xe 133 ?
Xe 133 is inhaled and it distributes evenly in the alveolar space
radiograph shows that the apex is fainter showing that it well ventilated
How can we measure perfusion using Xe 133 ?
Xe 133 is injected and leaves the blood quickly as it is poorly soluble - via the lungs
radiograph shows that apex is poorly perfused
How would a pulmonary embolus appear on a Xe radiograph ?
embolus blocks perfusion - no gas transfer - no stain
What is the pattern of blood flow from the base to the apex ?
blood flow decreases from the base the apex
What is the response of the lung to a high V/Q ?
vasodilation - increase blood flow to remove co2
bronchoconstriction- reduce air flow so that V and Q are matched
What is the response of the lung to a low V/Q ?
bronchodilation - increase oxygen and remove carbon dioxide as there is a lot of perfusion
hypoxic pulmonary vasoconstriction - allows more oxygen to enter the blood as it lowly ventilated
Hypoxic pulmonary vasoconstriction occurs where ?
pulmonary arterioles
What happens in the systemic circulation during hypoxic conditions ?
vasodilation
What type of response is hypoxic pulmonary vasoconstriction ?
local
What is HPV independent of ?
autonomic nervous system
What is HPV still responsive after ?
sympathectomy
vagotomy
chemoreceptor destruction
How is an oxygen disbalance sensed in smooth muscle cells ?
cells sense a disbalance between ATP and ADP
moreADP means low o2
ADP to AMP to AMP kinase
affects membrane potential via a voltage gated channel
allows calcium to enter via voltage gated channels
How is the V/Q mismatch balanced again ?
reduction in oxygen supply to the alveolus
reduced oxygen gradient into the blood
blood not fully oxygenated
pulmonary capillary constriction
blood supply rediced in the hypoxic region and diverted to the well oxygenated areas
Why is there a lower pressure of oxygen in the pulmonary capillaries compared to the arteries ?
anatomical shunt (blood from systemic arterioles drains directly into pulmonary veins) V/Q mismatch
What is venous admixture ?
occurs when the blood passes through the lung withour being oxygenated properly
What can left ventricular heart failure lead to ?
increase in pulmonary pressure due to backlog
hydrostatic pressure/oncotic pressure balance disturbed
water is trapped - pulmonary odema
What happenns in asthma ?
bronchoconstriction - harder to exhale
What happens in emphysema ?
surrounding tissue doesn’t support bronchioles - bronchioles collapse
What are the dangers of giving oxygen ?
the o2 dissociation curve predicts that even at higher o2 concentrations not much more H b is saturated
increased o2 reduces ventilation
causes co2 retention
acidosis
all the o2 may enter the elveoli whilst co2 doesnt leave the blood - ateclasis
How does ventilation change with work rate ?
ventilation increases linearly with work rate
What happens when peak oxygen consumption has been reached ?
body reverts to glycolysis to get more energy
What are the changes to ventilation during exercise ?
increase in tidal volume
increase in ventilation rate
increased diffusion capacity
increased recruitment of capillaries for GE
Why does arterial pH continue to drop even when carbon dioxide levels drop ?
lactic acid production
What stimulates pulmonary ventilation in exercise ?
motor cortex
proprioceptors and the muscle spindle
lung stretch receptors
increase in K concentration due to repolarisation
What is the most adaptive response to low O2 ?
hypoxic response
low o2 detected by peripheral chemoreeptors in the aortic body and the carotid bodies
signal to the respiratory centre in the medulla
causes hyperventialtion
What are the consequences of hyperventilation ?
blows off extra co2 increase in pH leading to alkalosis increases affinity for 02 decrease in c02 reduces the ventilatory drive mediated by central chemoreceptors
How is pulmonary oedema caused at high altitude ?
low 02 triggers HPV
this increases pulmonary pressure
disturbs the balance between oncotic and capillary pressure
leads to fluid
What is the long term adaptation to high altitude ?
bicarbonate is transported out of the CSF
this reduces the pH of the CSF
resets central chemoreceptors and makes them more sensitive to co2
increase ventilatory drive
What takes care of the bicarbonate concentrations in the blood ?
kidney
What doe ssutained hypoxia trigger ??.
the release of 2,3 DPG
shape of the o2 dissociation curve moves to the right
leads to a lower affinity for 02 so that it is readily released in the tissues
How is 02 carrying capacity increased at high altitude ?
hypoxia stimulates erythrocyte production
EPO is released from the kidneys
haemopoiesis in the bone marrow
50% increase in RBC levels
What are the consequences of having higher RBCs levels in the blood ?
increased viscosity of blood
heart has to pump harder
What leads to frostbite and gangrene ?
peripheral vasoconstriction in lower temperatures
reduces the circulation of blood
What are the short term changes to high altitude ?
increased pulmonary pressure
promotes recruitment of more capillaries
number and size of mitochondria increase - more aerobic metabolism
What are the long term changes to high altitude ?
body develops more capillaries in response to high altitude - increases oxygen diffusion
What are the early changes in response to high altitude ?
increased ventilation
increased HR
increased 2,3 DPG
What are the later changes to high altitude ?
increased RBCs
If the diameter of a bronchiole is halved , the flow drops by a factor of ?
16
pouiselles law
Lung compliance is ?
change in volume/ change in pressure
Which disease increases lung compliance ?
emphysema
Average arterial co2 pressure is ?
40 mmHg
Average arterial o2 pressure is ?
100 mmHg
What balances the V/Q mismatch ?
hypoxic pulmonary vasoconstriction
What do peripheral chemoreceptors sense ?
02 below 60 mmHg
