BIOL1040 Lecture Notes - Lecture 5: Cardiovascular Disease, Diastole, Atherosclerosis
Module 5 - circulation and gas exchange
Lecture 1
Gas exchange
Partial pressure
Partial pressure (pp) = the pressure exerted by a particular gas in a mixture of gasses
E.g. Usually air contains 21% O2 and, at sea level, atmospheric pressure = 760mmHg = 101
kPa
oHence, pO2 = 0.21 x 760 = 160 mmHg = 21.2kPa
Partial pressure applies to liquids (Henry's Law)
oSolubility of gas in liquid is directed proportional to pp of that gas in equilibrium with
the liquid (e.g. 4-8mL O2/L of marine and freshwater environments)
Gases diffuse from regions of high partial pressure to regions of low partial pressure
Respiratory organs for gas exchange:
Gills
oMarine worm… parapodium functions as gill
oSea star
oCray fish
Tracheal systems - insects
Lungs - mammalian respiratory system
Breathing ventilates lungs
Amphibia - positive pressure breathing
Mammals - negative pressure breathing
oThe pleural sac forms a double membrane surrounding the lung, similar to a fluid-
filled balloon surrounding an air-filled balloon.
Negative pressure breathing
Lung volumes
Regulation of breathing in humans
Mechanisms for transport of large quantities of O2 and CO2
Gases diffuse down pressure gradients
oFick's law of diffusion
oDepends on differences in partial pressure of gases
Respiratory pigments transport gases in blood
oOvercome the low solubility of gases in blood
oHemocyanin - arthropods, molluscs
oHaemoglobin - many invertebrates, all vertebrates
oIncrease FROM 4.5mL dissolved O2/L blood TO 200mL O2 carried by respiratory
pigments/L of blood in mammals
oNote: use 2L O2 pre minute during intense exercise
Coordination of circulation and gas exchange
Partial pressures of O2 and CO2 vary
oIn different parts of the circulatory system
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oIn inhaled compared with exhaled air
Inhaled air pO2 160mmHg, pCO2 0.2mmHg
Exhaled air pO2 120mmHg, pCO2 27mmHg
Loading and unloading of respiratory gases
Role of respiratory pigments: how does haemoglobin transport O2
Positive cooperativity is critical for the function of haemoglobin
Role of respiratory pigments: haemoglobin dissociation and PO2
Role of respiratory pigments: haemoglobin dissociation and pH
Role of respiratory pigments: maternal and foetal haemoglobin
So, what is special about diving mammals?
Store large amounts of O2
oLarge volume of blood
oHuge spleen - store 24L of blood
oHigh concentration of myoglobin in muscles
Adaptations to conserve O2 during a dive
oDecrease heart rate
oDecrease blood supply to muscles
Illusion of 2 related themes
oShort term response to environment
oLong term natural selection
Lecture 1: the heart
Circulation and gas exchange: cardiovascular system
Diffusion vs. circulatory system
Cells constantly exchange O2 and nutrients for CO2 and waste
Diffusion becomes inefficient
Circulatory system overcomes this limitation
Open vs. closed circulatory systems
A. An open circulatory system
B. A closed circulatory system
Advantages:
Open circulatory system:
oSimple, easy to maintain
oLess energy/lower pressures
Closed circulatory system:
oHigher pressures = increases efficiency for meeting high metabolic demand
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Document Summary
Partial pressure (pp) = the pressure exerted by a particular gas in a mixture of gasses. Usually air contains 21% o2 and, at sea level, atmospheric pressure = 760mmhg = 101 kpa: hence, po2 = 0. 21 x 760 = 160 mmhg = 21. 2kpa. Partial pressure applies to liquids (henry"s law) o. Solubility of gas in liquid is directed proportional to pp of that gas in equilibrium with the liquid (e. g. 4-8ml o2/l of marine and freshwater environments) Gases diffuse from regions of high partial pressure to regions of low partial pressure. Gills: marine worm parapodium functions as gill o o. The pleural sac forms a double membrane surrounding the lung, similar to a fluid- filled balloon surrounding an air-filled balloon. Mechanisms for transport of large quantities of o2 and co2. Fick"s law of diffusion: depends on differences in partial pressure of gases.
