Physiology Flashcards
The pneumotaxic centre is stimulated when…
a. ventral respiratory neurons fire
b. ventral respiratory neurons stop firing
c. dorsal respiratory neurons fire
c. the pneumotaxic centre is stimualted when dorsal respiratory neurons fire.
The ventral respiratory group neurons…
a. are activated during normal breathing
b. are activated during hyperventilation
c. are activated during apnoea
b. are activated during hyperventilation
FEV1/FVC ratio is less than 75% in restrictive lung diseases - true or false?
false as both the FVC and FEV1 both fall, the ratio of remains at a normal level
What higher centres in the brain influence respiratory centres?
cerebral cortex, limbic system, hypothalamus
A measure of effort that has to go into stretching or distending the lungs
Compliance
what is PAO2 at sea level approx?
100mmHg
If there is a decrease in blood pressure, the is a(n) _______ in ventilation
increase
During inspiration, which neurons are excited?
dorsal respiratory group neurons
What is a peak flow meter?
a device which the patient gives a sharp fast blow after maximal inspiration gives an estimate of airway function best of 3
Conditions where the Bohr Effect might come into play?
- increased PCO2
- increased H+
- increased temperature
- increased 2,3-biphosphoglycerate
Three pressures important for ventilation
Atmospheric Intra-alveolar Intra-pleural
the proportion of the FVC expired in first second
FEV1/FVC ratio
Why is the Bohr Effect useful?
allows oxygen offloading without the need for a drop in PO2
According to La Place’s law…
smaller alveoli with a smaller radius have a higher tendency to collapse as there is a greater inwardly directed collapsing pressure
Afferent discharge from irritated airwasy stimulates what reaction from the medulla…(4)
- short intake of breath
- closure of larynx
- contraction of abdominal muscles
- opening of larynx and expulsion of air at high speed
FEV1/FVC ratio is less than 75% in obstructive lung diseases - true or false
true
What are the 4 stages of External Respiration?
- Ventilation
- Gas Exchange between Alveoli and blood Gas
- Transport in the blood
- Gas Exchange in the tissues
What is the difference in oxygen dissociation in myoglobin?
hyperbolic curve as only dissociates at very low PO2
What is a pneumothorax?
air in the pleural space
The transfer of gases between the body and atmosphere depends upon….
ventilation perfusion
Normal CI
2.4-.42L/min/m2
At a normal PaCO2 of around 40mmHg, PAO2 =
100mmHg
How do we work out the partial pressure of O2 in the atmosphere?
21% of 760mmHg = 160mmHg which is breathed in
What is the body’s normal response to acute hypoxia?
hyperventilation and increased CO
How is the Oxygen dissociation curve affected in HbF?
shifted to the left
Other non-respiratory functions of the resp. system (7)
- water loss and heat elimination - enhanced venous return - normal acid-base balance maintenance - speech, singing, vocalisations - defence against inhaled foreign matter - modification and removal of materials passing through - nose as an organ of smell
At the lungs, O2 binding Hb ______ the ability of Hb to bind CO2 and H+
Weakens
The flat upper portion of the oxygen dissociation curve is important as it means a _______ fall in O2 will not affect oxygen _____ onto _______
moderate, loading, haemoglobin
Alveolar ventilation (L) =
(tidal volume - dead space) x resp. rate
In systemic arterioles, a decrease in O2 will cause vasodilation to…
promote offloading of oxygen to the tissues
Where are central chemoreceptors located?
near the surface of the medulla
The aortic and carotid bodies sense the _____ of ______ and _____ and the concentration of ___ in the blood
tension, oxygen, carbon dioxide, H
What does the Haldane effect work in tandem with?
The Bohr Effect
Residual Volume
minimum volumes of air remaining in the lungs even after a maximal expiration 1200ml
Average intra-pleural pressure at rest
756mmHg
Parasympathetic stimulation causes bronchodilation and and decreased resistance - true or false?
false PS stimulation causes bronchoconstriction and increased resistance
CO2 has a smaller partial pressure gradient, how is this offset so that CO2 still moves freely between the blood and alveoli?
it is 20x more soluble in membranes as it has a higher diffusion coefficient
What is external respiration?
sequence of events that leads to exchange of O2 and CO2 between the external environment and the cells of the body
Which particular gas is very regulated in respiration?
CO2
Why is alveolar ventilation more important?
it represents the new air available for gas exchange with blood.
What might a large difference between alveolar and arterial O2 partial pressure indicate?
issues with gas exchange or a right to left cardiac shunt
H+ dissociates from CO3- to join
Hb –> HbH
How much oxygen is carried by 1g of Hb when fully saturated?
1.34ml
Average intra-alveolar pressure during inspiration
759mmHg
What are the muscles of active expiration?
internal intercostals abdominal muscles
H+ drive of respiration is driven by the _______ chemoreceptors
peripheral
Anatomical dead space
where some inspired air remains in the airways and is not available for gas exchange
Why is CSF less able to buffer H+?
because there are less proteins
What allows the conversion of CO2 to bicarbonate to remain favourable?
chloride shift
What cannot pass through to the CSF via the blood brain barrier?
a. CO2
b. H
c. HCO3
H and HCO3
The CO2 diffuses easily and can generate H ions in the CSF as it is not so well buffered
The peripheral chemoreceptors are…
aortic and carotid bodies
In which situations is the hypoxic drive of respiration important?
- in patients with chronic CO2 retention
- at high altitudes
Inspiratory Capacity
The total volume of air that can be inspired 3500ml
Normally the work of breathing is ____% of total energy expenditure
3
apneusis
inspiration prolonged with brief expiration
How does binding of one O2 molecule affect haemoglobin?
increases its affinity for oxygen in a co-operative manner
What does Ficks Law of Diffusion tell us in respect to the movement of gases?
a large surface area and thin membrane is important for gas exchange
FEV1/FVC ratio
the proportion of the FVC expired in first second
alveolar pKa?
13.3kPa
PAO2 = PiO2 - [PaCO2/0.8]
partial pressure of O2 in alveoli
Active expiration during hyperventilation causes the dorsal neurons to…
excite the ventral respiratory group neurons
During inspiration the ______ and ______ expand as a result of contraction of _________ muscles
thorax, lungs, inspiratory
Atmospheric pKa?
21kPa
Where can rhythm of breathing be modified?
The Pons
Factors affecting rate of gas exchange (4)
- partial pressure gradient of O2 and CO2 - Diffusion coefficient for O2 and CO2 - Surface area of alveolar membrane - Thickness of alveolar membrane
H+ drive of respiration is important in…
acid base balance
Surfactant _______ the surface tension of smaller alveoli preventing them from ________
lowers, collapsing into larger alveoli
where reduced Hb can bind more CO2 than HbO2 removing the O2 from Hb increases its ability to bind CO2 and CO2 generated H+
Haldane Effect
What are carbamino compounds?
when CO2 combines with a terminal amine group in blood proteins
Inspiratory Reserve Volume
Volume of air that can be breathed in if required during active breathing 3000ml
Accumulation of CO2 in the alveoli as a result of increased perfusion _______ airway resistance leading to ______ airflow
decreases, increased
Joint receptors in exercise cause…
an increase in ventilation
Factors that may increase ventilation during exercise (5)
- Reflexes from body movement (joint receptors)
- Adrenaline release
- Impulses from cerebral cortex
- Increase in body temperature
- accumulation of CO2 and H+ generated by muscles
What body systems are involved in external respiration? (4)
- Respiratory
- Cardiovascular
- Haematology
- Nervous System
The ventral respiratory group neurons stimulate…
the internal intercostals and abdominals leading to forceful expiration
Total Lung Capacity
maximum volume of air that the lungs can hold TLC = VC + RV 5700ml approx.
tissues pKa?
5kPa
The presence of myoglobin in the blood is of no concern - true or false?
false it indicates muscle damage
What are the differences between HbF and HbA?
HbF has higher affinity for O2 and interacts less with 2,3-biphosphoglycerate
What is physiological dead space?
alveolar dead space + anatomical dead space
Residual volume ________ when the elastic recoil of the lungs is lost as it becomes difficult to get the air out i.e. in ________
increases, emphysema
Normal O2 concentration in arterial blood at rest
200ml/L
What is the primary determinant of oxygen saturation of haemoglobin with O2?
PO2
Surfactant acts to intersperse the water molecules lining the alveoli - true or false?
true
Work of breathing is increased by…(4)
decrease in pulmonary compliance airway resistance increase elastic recoil is decreased a need for increased ventilation
Sectioning where causes ventilation to cease?
below the medulla
Why does it not matter how much haemoglobin there is, if partial pressure is normal?
it will become saturated
A local tissue increase in O2 will cause systemic arterioles to ….
constrict - this avoids too much oxygen being offloaded where it is no longer needed
Forces keeping the alveoli open
Transmural pressure gradient Pulmonary surfactant Alveolar interdependence
Percentage of CO2 carried as carbamino compounds in the blood?
30%
Which particular blood protein forms a carbamino compound?
globulin
What is the average distance of interstitial space between the capillaries and alveolus?
0.5µm
What two forces hold the thoracic wall and lungs in close opposition?
- Intrapleural fluid cohesiveness
- Negative intrapleural pressure
Why does HbF have a higher affinity for O2 than HbA?
to allow foetus to hijack O2 from mother
the rate at which blood is passing through the lungs
Perfusion
How does foetal Hb differ from adult haemoglobin in structure?
has two gamma subunits instead
Cells that produce pulmonary surfactant
Type II alveoli
If the partial pressure in a gas phase is increased, the concentration of the gas in the liquid phase would decrease proportionally - true or false?
false According to Henry’s Law it would increase proportionally
Dynamic airway compression causes no problems in normal people. The _______ airway resistance causes an increase in airway pressure _______. This helps open the ______ by increasing the driving pressure between the ______ and _____.
increased, upstream, airways, alveolus, airway
Sectioning above the medulla
a. retains fairly normal ventilation
b. causes ventilation ceases
c. causes an abnormal breathing pattern
a - it retains fairly normal ventilation
Percentage of O2 bound to haemoglobin?
98.5%
The Pre-Botzinger complex, a group of neurons that display _______ activity near the upper end of the _______ respiratory centre
pacemaker, medullary
pulmonary compliance is reduced by factors such as…(5)
pulmonary fibrosis pulmonary oedema lung collapse pneumonia absence of surfactant
As gas volume increases, the pressure increases - True or False?
False
As gas volume increases, the pressure decreases allowing the air to move into the lungs as the intra-alveolar pressure decreases below that of the atmosphere
Why is alveolar ventilation less than pulmonary ventilation?
because of the anatomical dead space
What is the most important force for linking the lungs and the thorax?
negative intrapleural pressure
Functional Residual Capacity
Volume of the air in the lungs at the end of normal passive expiration 2200ml FRC = ERV + RV
Expiratory Reserve Volume
Extra volume of air that can be expired during forced expiration 1000ml
Oxygen content of arterial blood can be calculated as…
CaO2 = 1.34 x Hb x SaO2
Stimulation of peripheral chemoreceptors by H+ causes (2)
- hyperventilation
- increased elimination of CO2
Innervation of diaphragm
Phrenic nerve; C3,4,5
Henrys Law
the amount of a given gas dissolved in a given type and volume of liquid at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid
What adaptations do the lungs have to promote gas exchange?
large surface area promoted further by extensive alveoli and bronchial trees Extensive pulmonary capillary network
Amount of O2 dissolved in the blood at rest?
3ml/L
Main muscle of inspiration at rest
Diaphragm
Which effect does the Bohr Effect pair up with?
Haldane effect
Average intra-pleural pressure during inspiration
754mmHg
Where does the reaction that converts CO2 to bicarbonate occur?
in the red blood cells
PiO2
partial pressure of inspired air
What are the major muscles of inspiration?
external intercostal muscles diaphragm
How can respiratory distress syndrome of the New Born be prevented?
if prematurity is anticipated - provide mother with steroids to try and mature baby’s lungs
PaCO2
partial pressure of arterial CO2
Increased pulmonary compliance occurs in…
emphysema
What is internal respiration?
the intracellular mechanisms that consume oxygen and produces CO2
Average intra-alveolar pressure during expiration
761mmHg
Definition of alveolar ventilation
the volume of air exchanged between the alveoli and atmosphere per minute
difference between myoglobin and haemoglobin?
haemoglobin has 4 haem groups, myoglobin has one
Haemoglobin can for a _____ combination with O2 where each Hb molecule contains __ haem groups each of which can bind ____ molecule
reversible, four, one
The cough reflex is activated by…
irritation of the airways or tight airways in asthma
What is the cause of alveolar dead space?
when the ventilated alveoli are not adequately perfused with blood
What are the accessory muscles of inspiration?
sternocleidomastoid scalenus
the rate at which gas is passing through the lungs
Ventilation
Neurons from the apneustic centre excite…
the inspiratory area of the medulla and prolong inspiration
O2 consumption of our cells at rest
250ml/min
DO2I =
CaO2 x CI oxygen delivery index where CI is just CO accounting for body surface area
Why is negative intrapleural pressure so important for linking the lungs and thorax?
the sub-atmospheric intrapleural pressure creates a transmural gradient forcing the lungs to expand outwards.
Forces promoting alveolar collapse
Elasticity of stretched pulmonary connective tissue Alveolar surface tension
Compliance
A measure of effort that has to go into stretching or distending the lungs
What is ventilation?
the mechanical process of moving air between the atmosphere and alveolar sacs
If an alveolus starts to collapse, the surrounding alveoli are ______ and then ______ exerting expanding forces on the collapsing alveolus to ______ it
stretched, recoil, open
Daltons Law of Partial Pressures
The total pressure exerted by a gaseous mixture = the sum of the partial pressures of each individual component in gas mixture
Vital Capacity
maximum volume of air that can be moved out during a single breath following a maximal inspiration 4500ml VC = IRV + TV + ERV
the amount of a given gas dissolved in a given type and volume of liquid at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid
Henrys Law
Dorsal respiratory group neurons excites which muscles?
Inspiratory muscles
Diaphragm
External Intercostals
Dynamic Airway Compression Pressure applied to the _______ helps to push air out of the lungs, whereas pressure applied to the ______ is not desirable as it tends to compress it. The rising pleural pressure during _____ expiration compresses the _______ and _______ which is known as dynamic airway compression
alveolus, airway, active, alveolus, airway
What is chloride shift?
the switching of Cl and CO3- so that the bicarbonate is moved to the blood
Stimulation the _______ _____ terminates inspiration
Pneumotaxic centre
Tidal Volume
Volume of air inspired and expired during normal passive breathing 500ml
Why are diseases airways not able to cope with dynamic airway compression?
the driving pressure is lost over the obstructed segment. This causes a fall in airway pressure downstream resulting in airway compression by the rising pleural pressure.
Sympathetic stimulation causes ________ and ________ resistance
bronchodilation and decreased
Definition of pulmonary ventilation
the volume of air breathed in and out per minute
The majority of CO2 is carried in solution in the blood - true or false?
false the majority is carried in bicarbonate
The less compliant the lungs are, the more work is required to produce a degree of inflation - true or false
true
To increase pulmonary ventilation, both the depth (_____ _____) and rate of breathing increase. Because of dead space, it is more advantageous to increase the _______.
tidal volume, depth
Hering-Breur Reflex
Stretch receptors in the walls of the bronchi/bronchioles that reflex guards against hyperinflation
Patients with Heart Failure will get SOB before….
pulmonary oedema occurs
Perfusion
the rate at which blood is passing through the lungs
What is Respiratory Distress Syndrome of the New Born?
where newborn lungs are unable to produce the pulmonary surfactant to reduce the alveolar surface tension and thus have to make strenuous inspiratory efforts
Gases move across cell membranes by….
pressure gradients
Where is myoglobin present?
skeletal and cardiac muscles
What allows the lungs to relax and recoil?
elastic connective tissue alveolar surface tension
The graph for oxygen dissociation curve is….
sigmoidal
The hypoxic drive of respiration is completely through central chemoreceptors - true or false?
false
it is entirely through peripheral chemoreceptors
What is the Haldane Effect?
where reduced Hb can bind more CO2 than HbO2 removing the O2 from Hb increases its ability to bind CO2 and CO2 generated H+
Muscles of active inspiration
external intercostals - contraction lifts ribs and moves out sternum
Chronic adaptations to hypoxia (5)
- increase in RBC production
- Increase 2,3BPG produced within RBC - increases O2 offloading
- Increase no, of capillaries
- Increase no, of mitochondria - use O2 more efficiently
- Kidneys conserve acid - decrease arterial pH
Oxygen delivery to the tissues can be impaired by… (3)
respiratory disease Anemia Heart Failure
Partial pressure of inspired O2 depends on total pressure and proportion of CO2 in the gas mixture - true or false?
false proportion of O2 - around 21% in atmosphere
Pulmonary ventilation (L) =
tidal volume x resp. rate
Increased _________ ___ as a result of increased ventilation causes pulmonary _______ which increases blood flow to match a larger airflow
alveolar O2, vasodilation
Boyle’s Law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
What is the primary determinant of airway resistance?
the radius of the conducting airway
when are pulmonary stretch receptors likely to be activated?
during active inspiration where tidal volumes are >1L
The Bohr Effect causes a left shift in the oxygen-dissociation curve - true or false?
false it causes a right shift as it becomes easier for O2 to dissociate even at higher PO2s
Hypoxia at high altitudes is caused by…
a decreased partial pressure of inspired oxygen (PiO2)
What can increased pulmonary compliance be a result of?
elastic recoil loss
The steeper lower part of the oxygen dissociation curve is important as it allows _______ ______ to get a lot of oxygen for a _____ drop in PO2
peripheral tissues, small
Influence the respiratory centres (6)
Higher brain centres
Stretch receptors in the bronchi/bronchioles
Juxtapulmonary receptors
Joint receptors
Baroceptors
Central and Peripheral Chemoreceptors
Pre-Botzinger complex
a network of neurons which controls rhythms
In healthy people, alveolar dead space is of great importance - true or false?
false alveolar dead space should be minimal in a healthy individual
Ventilation
the rate at which gas is passing through the lungs
What types of pneumothorax can occur?
traumatic (wound to chest wall) spontaneous (lung side)
Rhythm for inspiration followed by expiration is generated by the _______
medulla oblongata
Surfactant is a mixture of proteins and carbohydrates - true or false?
False Surfactant is a mixture of proteins and lipids
Decreased pulmonary compliance may cause a _______ pattern of lung volumes in spirometry
restrictive
Enzyme that converts CO2 and H2O to carbonic acid
carbonic anhydrase
Average intra-alveolar pressure at rest
760mmHg
Pneumothorax abolishes the ___________ and causes the lung to ______
transmural gradient, collapse
