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### 36 Cards in this Set

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 Does a low, or high linear flow rate lead itself to laminar flow? A low linear flow rate (flow rate in volume/second / Cross sectional area How do you work out linear flow rate? Flow rate (volume/second) / Cross sectional area In laminar flow, resistance to flow is constant for a tube of given dimensions T/F T When airflow is turbulent, resistance increases with flow rate T/F T When cross sectional area increases, resistance to flow decreases/increases Decreases The greatest resistance to airflow is found in the segmental bronchi (gen. 4). Why? The CSA is relatively low and the airflow is high (and turbulent) Remember linear flow rate equation Airway resistance falls as volume of the lungs increases. How? There is an increased total cross sectional area (imagine breathing through a woolly jumper - and remember some branches of the respiratory tree can poly-furcate (i.e. more than bifurcate) In the 3D respiratory system, work done = delta(pressure) * delta(volume) WD = F * D Why is the work of breathing increased with decreased compliance? More work has to be done by the inspiratory muscles to expand the chest Why is there increased airflow resistance in rapid, shallow breathing compared with deep and slow breathing? (In the space of a minute) In rapid breathing, more breaths are taken per minute. More breaths --> More resistance Why does pulmonary fibrosis result in increased rate and decreased depth of breathing? It minimises work. The work of expanding the chest is increased (because of the fibrosis). To compensate, more breaths are taken, but to a shallower degree State LaPlace's law Pressure (P) inside a hollow sphere is twice the surface tension (T) divided by the radius (r) P = (2T)/r 'Pressure (P) inside a hollow sphere is twice the surface tension (T) divided by the radius (r) P = (2T)/r' Is whose law? LaPlace's law State Poiscellie's law R = (8nl)/(pi)r^4 R = resistance n = viscosity l = length r = radius Give three functions of surfactant Stabilising the alveoli by reducing the surface tension of the air-liquid interface (nice) Increasing compliance of the lung Prevents fluid accumulating in the alveoli (and therefore plays an important role in keeping the alveolar air space dry) What is surfactant made up of? Many phospholipid molecules A micelle is a monolayer T/F T Why is FEV(1) reduced in an obstructive lung disease? It takes longer to exhale through narrowed airways (imagine breathing as hard as you can through a McDonald's straw, then through a tube as wide as a jam-jar. Alternatively, pursed and wide mouth) FEV(1) is reduced in an obstructive lung disease T/F T What will the vital capacity of an individual with a restrictive lung disease be like? Normal or reduced? Reduced Those with a restrictive lung disease have a reduced PEFR T/F F (those with an obstructive lung disease do) Airways resistance increases as lung volume decreases T/F T What are the three main factors that affect lung volumes? (Generic) Body size Age Sex In the standing position, is the apex or base more ventilated? The base - Around 50% more What is the 'diffusion potential'? The potential across a membrane arising from the steady-state diffusion of an ion What is the 'equilibrium potential'? The membrane potential at which a certain ion has no net movement through a membrane. What is the membrane potential? The difference in voltage between the interior and exterior of a cell What is the name for the membrane potential of an unstimulated (quiescent) cell? The resting membrane potential What does the Nernst equation calculate? The equilibrium potential What is the voltage scale of a nerve cell action potential? -70 to +40 mV What last longer - nerve and skeletal action potentials, or cardiac action potentials? Cardiac action potentials last much longer (150 - 300 ms) Other APs last around 1 - 2 ms What is the voltage scale of the SAN? -60 to 0 mV (-60 immediately after an AP - threshold is at -50 mV) How long does a SAN action potential last for? 150 - 200 ms What does membrane potential equal? V(inside) - V(outside) V = voltage What causes the upstroke (depolarisation) in a SAN action potential? Is it the same for atrial and ventricular action potentials? Diffusion of CALCIUM into the cell with SAN AP (K+ still causes the repolarisation) Others are the normal sodium What is more concentrated outside of the cell, Na+ or K+? Na+! (At the resting state!)