Physiology - Intro Flashcards
Define respiration.
Exchange of oxygen and carbon dioxide between the environment and tissues
Describe what respiration can be divided into.
External - exchange of oxygen and carbon dioxide between the atmosphere and blood flowing through the lungs
Internal - transport of oxygen and CO2 between the tissues and lungs by the circulating blood. O2 consumption and CO2 production in tissues.
Name the five steps of respiration.
Ventilation Gas Exchange Gas Transport Gas Exchange Cellular Respiration
Define ventilation.
Process of moving air in and out of the lungs in order to supply oxygen and remove carbon dioxide from the alveoli.
Process of BULK FLOW
Define the first gas exchange in the process.
Describes how O2 and CO2 moves across the alveoli membrane down their partial pressure gradients.
Process of DIFFUSION
Define gas transport.
Blood leaves the lungs high in O2 and low in CO2.
Pumped around the body by a process of BULK FLOW.
Describe the second gas exchange.
At the interface between the capillaries and the cells there is exchange of O2 and CO2 down their partial pressure gradients.
Process of DIFFUSION
Define cellular respiration.
Cells use O2 and produce CO2.
What is Dalton’s Law of Partial Pressures?
Pgas = Fgas x Ptotal
Need to know the % of concentration of each gas and the atmospheric pressure.
Normally use 760mmHg
** see lecture slides and make a note to paste on wall
What does water vapour do in the trachea?
Reduces the PO2 in the trachea by about 10mmHg
How do we calculate the pressure of inspired O2? (PIO2)
PIO2 = FIO2 x (barometric pressure - 47)
How do we calculate the ventilation?
VE= f x VT
Why do we calculate alveolar ventilation?
Not all the inspired air reaches the alveoli - as fresh air is inhaled, it is mixed with air in the anatomical dead space.
How do we calculate alveolar ventilation?
VA = f x (VT - D)
What does alveolar ventilation measure?
Measures the flow of fresh gases into and out of the alveoli during a particular time
What type of breathing increases/decreases alveolar ventilation?
Slow deep breathing increases VA
Rapid shallow breathing decreases VA
What is the primary principle of ventilation?
Air moves from an area of higher pressure to an area of lower pressure.
Describe the pressures causing inspiration.
Lower pressure inside lungs
Higher pressure outside lungs
Describe the pressures causing expiration.
Higher pressure inside lungs
Lower pressure outside lungs
Describe what happens on inspiration/expiration.
Volume changes
Pressure changes
Gas flow and pressure equalization
What does Fick’s Law of Diffusion explain?
Explains gas exchange through the membranes.
How does pulmonary disease impair gas transfer capacity?
Thickening of the alveolar membrane e.g. pulmonary fibrosis
Reduction in SA e.g. emphysema (destruction of alveoli = reduced SA)
Name the five mechanisms causing arterial hypoxaemia.
Reduced PB or FIO2 Hypoventilation Impaired diffusion Shunt V/Q mismatch (ventilation, perfusion)
What two forms is oxygen carried in the blood?
Dissolved and combined with Hb
What is the O2 capacity?
Maximal amount of O2 that can be combined with Hb
Describe the oxygen Hb combination.
Easily reversible to give oxyhaemoglobin
O2 + Hb HbO2
How much oxygen can one gram of Hb combine to?
1.34ml O2
How many grams of Hb does a normal litre of blood have?
150g of Hb
How do we calculate the O2 capacity?
Grams of Hb x 1.34ml O2
How is CO2 transported?
Dissolved in plasma - 10%
Transported as HbCO2 (20%)
Transported as HCO3- (bicarbonate dissolved in plasma - 70%)
What is the central controller of respiration?
Pons, medulla and other parts of the brain
What are the effectors of respiration?
Respiratory muscles
What are the sensors of respiration?
Chemoreceptors, Lung and other receptors (stretch)
