Physiology 1 & 2 Flashcards
Internal respiration?
Intracellular mechanisms that produce O2 and use CO2
External respiration?
Sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body
4 steps of external respiration?
Ventilation (mechanical process of moving air into and out of the lungs)Gas exchange between the alveoli and bloodGas transport in blood (between lungs and tissue)Gas exchange at tissue level
Boyle’s law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
Why does air move into the lungs during inspiration?
During inspiration, the inspiratory muscles contract causing the thorax and lungs to expand. This causes the intra-alveolar pressure to become less than the atmospheric pressure due to Boyle’s law causing air to flow down the concentration gradient into the lungs
What holds the thoracic wall and lungs in close proximity? (2)
Intrapleural fluid cohesivenessNegative intrapleural pressure
What is the intracellular fluid cohesiveness?
Water molecules in intrapleural fluid are attracted to each other and resist being pulled apart causing the plural membranes to stick together
Negative intrapleural pressure?
The intracellular pressure is below atmospheric pressure which creates a transmural pressure gradient forcing the lungs outwards and chest inwards
Atmospheric pressure value?
760mmHg
Intralveolar pressure value?
760mmHg
Intrapleural pressure value?
756mmHg
Is inspiration an active or passive process?Expiration?
ActivePassive
Major inspiratory muscle?
Diaphragm
Inspiratory muscles?
Diaphragm and external intercostal muscles
what gives motor innervation to the diaphragm?
Phrenic nerves formed from C3, 4, 5 nerve roots
When does air stop entering the lungs?
When intra-alveolar pressure equals atmospheric pressure
How does expiration occur?
Relaxation of the inspiratory muscles causes the chest wall and lungs to recoil to their perspiratory size due to their elastic propertiesThis causes the intra-alveolar pressure to rise due to boyle’s law forcing air out of the lungs down the pressure gradient until intra-alveolar pressure = atmospheric pressure
Pneumothorax definiton
Air in the pleural space (causes the lung to collapse)
Types of pneumothorax?
Traumatic (hole in chest wall)Spontaneous (hole in lung wall)
What causes a lung to recoil during expiration?
Elastic connective tissueAlveolar surface tension
Alveolar surface tension?
Attraction between water molecules at liquid air interface
What reduces the alveolar surface tension?
Surfactant (lowers surface tension of smaller alveoli more than larger alveoli)
La Place’s law?
P=2T /r (the smaller alveoli have a higher tendency to collapse)
What is surfactant made of?
Lipids and proteins
What is surfactant secreted by?
Type II alveolar cells
Respiratory distress syndrome of the newborn?
Developing metal lungs are unable to synthesise surfactant until later in the pregnancy meaning premature babies may not have enough surfactant
What helps to keep the alveoli open?
SurfactantAlveolar interdependancetransmural pressure gradient
What is alveolar interdependence?
If an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus
When does respiration become active (2)?
Due to exercise or disease
Accessory muscles of inspiration? (2)
SternocleidomastoidScalenus
What instrument is used to measure the air capacity of the lungs?
Spirometer
Tidal volume?Value for a normal healthy adult male
Normal volume of air displaced between normal exhalation and inhalation when extra effort is not applied 500ml
Residual volumeValue
Amount of air left in the lungs after a forced exhalation1200ml
Functional residual capacityValue
Volume air left in the lungs at the end of passive expiration 2200ml
Vital capacityValue
Maximum amount of air a person can expel from the lungs after a maximum inhalation4500ml
Total lung capacityValue
Most air you can inspire into your lungs5700ml
Inspiratory reserve volume Value
Additional air that can be forcefully inhaled after the inspiration of a normal tidal volume3000ml
Inspiratory capacityValue
volume of air that can be inspired after a normal expiration 3500ml
Expiratory reserve volumeValue
additional air that can be forcefully expired after the expiration of a normal tidal volume 1000ml
FEV1 full name and explanation?
Forced Expiratory volume in one second (dynamic volume)Volume of air that can be expired during the first second of expiration in an FVC
FVC stands forExplanation
Forced vital capacitymaximum volume that can be forcefully expelled from the lung following a maximum inspiration
FEV1 % (ratio) =
FEV1/FVC
What type of curve can be used to determine FVC and FEV1
Volume time curve
FEV1/FVC normal and asthmatic
Normal = >75%Asthmatic (obstructive) =
FVC and FEV1 for restrictive disease
FVC = lowFEV1 = lowRatio = normal
Airway flow =
F= change in pressure/ Resistance
Sympathetic/ parasympathetic stimulation causes bronchoconstriction/ bronchodilation
Para. = bronchoconstrcitonSym. = bronchodilation
Does airway resistance make it more difficult to inspire or expire
Expire
What happens to the intracellular pressure during inspiration and expiration?
Inspiration = fallsExpiration = rises
Why are the alveoli and airways compressed during active expirationWhat is this calledWho does this cause a problem for
Due to rising pleural pressureDynamic airway compressionPatients with airway obstruction
What helps push air out of compressed airways
Increased pressure upstream increases the driving pressure between the alveolus and airway therefore pushing air out of the alveoli
What happens during dynamic airway compression if there is an obstruction?
The driving pressure is lost over the obstructed segment causing a fall in the airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration (made worse if patient also has decreased elastic recoil of the lungs)
What is a peak flow meter useful for assessing patients with?
Obstructive conditions
Pulmonary compliance
measure of the effort that has to go into stretching or distending the lungs (volume change per unit of pressure change across the lungs)
What does less compliant lungs mean?
More work is required to produce a given degree of inflation
Some factors that decrease pulmonary compliance
pulmonary fibrosiSPulmonary oedemaLung collapsePneumoniaAbsence of surfactant
What type of pattern can decreased compliance show in spirometry
Restrictive pattern
When can compliance become abnormally increased
When the elastic recoil of the lungs is lost e.g. emphysema
What happens to compliance as you age
It increases
4 situations when work of breathing is increased
Pulmonary compliance is decreasedAirway resistance is increasedElastic recoil is decreasedneed for increased ventilation
