Respiratory Physiology Flashcards
what is internal respiration
intracellular mechanisms which consume O2 and produce CO2
what is external respiration
sequence of events that lead to the exchange of O2 and CO2 between external environment and cells of the body
four steps of external respiration
- ventilation between atmosphere and alveoli
- O2 and CO2 exchange between alveoli and blood
- transport of O2 and CO2 between lungs and tissues
- exchange of O2 and CO2 between blood and tissues
what is ventilation?
mechanical process of moving air between atmosphere and alveoli
pressure change for ventilation to occur? (boyle’s law)
intra alveolar pressure must be less than atmospheric pressure
2 forces that hold thoracic wall and lungs close
- intrapleural fluid cohesiveness
2. negative intrapleural pressure (lungs force out, chest forced in)
muscles of inspiration and function
- external intercostal muscles, elevates ribs and sternum
- diaphragm, lowers to increase size of thoracic cavity
expiration - passive of active?
passive
what abolishes the transmural pressure gradient?
pneumothorax
what causes lungs to recoil?
- elastic connective tissue
2. alveolar surface tension
what is alveolar surface tension?
water and air molecules are attracted in the alveoli, which produces a force that resists stretching
what is surfactant and what does it do?
- it is secreted by type II alveoli
- it lowers alveolar surface tension, as it mixes with water molecules lining the alveoli
What does LaPlace’s law state?
smaller alveoli have a higher tendency to collapse
what is alveolar interdependence?
if an alveolus begins to collapse, surrounding stretch to pull the collapsing one open
what does parasympathetic stimulation do to the airways?
causes bronchoconstriction
what does sympathetic stimulation do to the airways?
causes bronchodilatation
what is pulmonary compliance?
this is a measure of how much effort goes into stretching or distending the lungs
what is alveolar ventilation?
the volume of air exchanged between the atmosphere and alveoli per minute
what is pulmonary ventilation?
the volume of air breathed in and out per minute
what is alveolar dead space?
this is ventilated alveoli which are not adequately perfused with blood
effect on systemic arterioles in decrease/increase of O2?
vasodilation/vasoconstriction
effect on pulmonary arterioles in decrease/increase of O2?
vasoconstriction/vasodilation
four factors influencing rate of gas exchange across alveolar membranes?
- partial pressure gradient for O2 and CO2
- diffusion coefficient for O2 and CO2
- surface area of alveolar membrane
- thickness of alveolar membranes
how is oxygen present in the blood?
- bound to Hb
- physically dissolved
what is the Bohr Effect?
- shift of the sigmoid Hb saturation curve to the right
- occurs in active tissues, where increased release of O2 is needed
what four factors increase the release of O2 at tissues?
- increased PCO2
- increased H+ conc
- increased temp
- increased 2,3 BDP
what does foetal haemoglobin do to the Hb curve?
shifts to the left (higher affinity for O2)
how is CO2 transported in the blood?
- in solution (10%)
- as bicarbonate (60%)
- as carbamino acid (30%)
what is the haldane effect?
removing O2 from Hb increases the ability of Hb to pick up CO2 and H+
where is rhythm generated in the brain?
Pre-Botzinger complex in the medulla (causes inspiration), by stimulating dorsal
where is active expiration generated in the brain?
ventral neurones, which are stimulated by increased firing from dorsal
what, when stimulated, terminates inspiration?
pneumotaxic centre (in the pons)
what, when stimulated, prolongs inspiration?
apneustic centre
where are peripheral chemoreceptors?
carotid and aortic bodies
what do peripheral chemoreceptors do?
sense tension of O2, CO2 and H+ in the blood
where are central chemoreceptors?
situated near the surface of the medulla in the brainstem
what do central chemoreceptors do?
they respond to H+ of the cerebrospinal fluid
- only CO2 diffuses across the blood/brain barrier
what effector causes the hypoxic drive of respiration?
peripheral chemoreceptors, when PO2 falls below 8.0kPa
what effector causes the H+ drive of respiration?
peripheral chemoreceptors (cause hyperventilation, as there will be increased CO2)
