Blood gas transport

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Fichas sobre Blood gas transport, creado por reynoldslaura el 10/05/2013.
reynoldslaura
Fichas por reynoldslaura, actualizado hace más de 1 año
reynoldslaura
Creado por reynoldslaura hace más de 11 años
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Resumen del Recurso

Pregunta Respuesta
Which part of the haemoglobin molecule does CO₂ bind? The 'globin' part (as opposed to O₂ which binds to the haeme part)
Which is more soluble in the blood HCO₃¯or CO₂ ? HCO₃¯
What is a 'chloride shift'? The diffusion of Cl¯ ions into the red blood cell to maintain an electrical balance due to loss of HCO₃¯into the plasma
What is the Haldane effect? It is when the removal of O₂ from Hb increases the ability of Hb to pick up CO₂ and CO₂ generated H⁺ . This further enhances O₂ oxygen release from Hb
What is the Haldane effect? It is when the removal of O₂ from Hb increases the ability of Hb to pick up CO₂ and CO₂ generated H⁺ . This further enhances O₂ oxygen release from Hb
How is PCO₂ impacted by pulmonary oedema? In pulmonary oedema the lungs fill with fluid therefore there will be an increase in PCO₂ as CO₂ can diffuse across fluid 20x more efficiently than O₂
Does hypercapnia or hypoxia lead to increased respiratory acidosis? Hypercapnia- increased PCO₂ levels
When can hypocapnia occur? In hyperventilation, when the rate of ventilation exceeds the bodies metabolic needs for CO₂ removal. This can be due to asthma, anxiety, fever and aspirin poisoning
What causes respiratory alkalosis? Hypocapnia
What is our narrow vital range of pH? 6.8-7.7
What pH is plasma or ECF maintained at? 7.4
What is the equation for calculating pH? -log[H⁺]
What is a non-volatile acid? An acid produced from sources other than CO₂ and is not secreted by the lungs. It is a metabolic acid therefore all the acids produced by the body are non volatile EXCEPT FOR CARBONIC ACID
Name the sole volatile acid produced by the body. Carbonic acid
Name two sources of hydrogen loss that will affect acid/base balance. Loss due to vomit and in the urine
Give some examples of ways in which we gain H⁺ ions. Via generation from CO₂, metabolism that leads to production of phosphoric acid, lactic acid, ketoacids and fatty acids etc and loss of bicarbonate ions via diarrhoea or in the urine
What is the ideal composition of acidic and alkaline foods in the diet? 40% acidic e.g. carbohydrates and protein and 60%alkaline e.g. fruit and veg
What are the symptoms of alkalosis? increased CNS activity presenting as 'pins and needles and dizziness'
What are the symptoms of acidosis? Decreased CNS activity, presenting as lethargy, coma and death
What is the difference between respiratory and metabolic acidosis/alkalosis? Respiratory affects PCO₂ levels whereas metabolic affects HCO₃¯ levels
What can cause metabolic acidosis? Diarrhea, diabetes, alcohol etc
What can causes metabolic alkalosis? Vomiting, excess of anti-acids (e.g. gaviscon) etc
How is blood pH kept closely regulated at 7.35-7.45? By 3 lines of defence. Via buffering (takes seconds), respiratory compensation -for metabolic disorder (takes minutes) and renal excretion- for respiratory disorder (takes hours/days)
Define buffer. A buffer is a mixture of substances in solution that can resist changes in hydrogen ion concentration when strong acids or bases are added
Do the three lines of defence act to correct the initial change in pH? NO but they act to MINIMISE the changes in pH
Name an example of a naturally occuring buffer. HCO₃¯ (transported out from cells in exchange for chloride therefore it results in an increase in H⁺) or plasma proteins (buffering occurs at specific amino acids) or phosphate (especially imp. in the kidney)
will doubling the partial pressure of oxygen double the % haemoglobin saturation? NO because the relationship between the two is not linear!
How will a rise in PO₂ from 20-60 mmHg impact Hb saturation? Although a small change as it is at the bottom of the oxygen dissociation curve it will result in a large increase in Hb saturation
What is the main factor that affects % haemoglobin saturation? PO₂
What are the other factors that affect affinity of O₂ for Hb (therefore haemogolobin % saturation)? CO₂, acidity, temperature and 2,3-bisphosphoglycerate
What effect does CO₂ have on %Hb saturation? It decreases the affinity of O₂ for Hb by binding to haemoglobin and changing its shape. More O₂ is released from Hb at any specific point as there is a decrease in % Hb saturation therefore more O₂ is released to tissues
What affect does acidity have on the haemoglobin dissociation curve? It shifts it to the right as acid/ H⁺ binds to Hb and reduces the infinity of O₂ for haemoglobin therefore more O₂ is delivered to the tissues
What is normal oxygen consumption in ml at rest? 250ml/min
What is the normal amount of CO₂ produced under resting conditions per min? 200ml/min
Explain Fick's law of diffusion. Diffusion rate of a gas through a sheet of tissue depends on the concentration gradient, the surface area and thickness of the membrane through which it is diffusing
What is the Bohr effect? The influence of CO₂ and acid on the release of O₂ from haemoglobin
What effect does an increase in temperature have on % Hb saturation? It reduces %Hb saturation, again to enhance O₂ release from Hb for use by more active tissues (Heat is often produced in response to exercising muscle or other actively metabolising cells)
Where is 2,3- BPG produced from? Inside red blood cells during active metabolism
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