Physiology 3120 Lecture Notes - Lecture 48: Respiratory Alkalosis, Respiratory Acidosis, Ph
15 May 2018
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Lecture 48 – Acid/Base Balance
- Through transport of CO2 as bicarbonate the lungs have a significant impact on blood pH
- pH = -Log[H+]
- More H+, more acidic, lower pH
- Normal blood pH is approx. 7.4
- Important for life (protein folding, enzyme activity etc)
- Lower than pH 7 and higher than pH 8 = die
- Maintaining Blood pH is very important
o Buffer systems in blood
o Lung (Ventilation)
o Kidneys
Buffer systems
- A buffer is a substance that can reversibly bind hydrogen ions
- Limits changes in pH to keep pH constant
- In the blood:
o Bicarbonate system LUNGS!!
▪ Most important aspect of buffering and maintaining blood pH
o Protein system
o Phosphate system
- Rapid (seconds/minutes)
o In contrast to the kidneys which are a slow process
o Lungs can affect pH rapidly by changing bicarbonate
Experiment
- Take blood and add different partial pressures of CO2 and measure pH and bicarbonate
- Normal: partial pressure of CO2 is 40 mmHg, pH is 7.4 and bicarbonate is at 24 mmol/L
- If you increase PCO2 (drive reaction to the right):
o pH decreases
o Bicarbonate goes up
- If you decrease PCO2 (drive reaction to left)
o pH increases
o Bicarbonate decreases
- Lungs can affect blood pH very rapidly
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Respiratory acidosis
- Blood has a lower pH than normal
- E.g drugs or diseases that respiration is reduced
- If alveolar ventilation is reduced, less CO2 is exhaled
o CO2 builds up in lungs and partial pressure in blood increases
o pH decreases and bicarbonate is high
Respiratory alkalosis
- Occurs at high altitudes
- Increase ventilation because you want more oxygen
- As a consequence, you get rid of more CO2 and partial pressure of CO2 decreases
- pH increases and bicarbonate decreases
- Through ventilation the lungs can affect blood pH effectively and rapidly
Role of kidneys
- Excretion of acids/base
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Through transport of co2 as bicarbonate the lungs have a significant impact on blood ph. Important for life (protein folding, enzyme activity etc) Lower than ph 7 and higher than ph 8 = die. Maintaining blood ph is very important: buffer systems in blood, lung (ventilation, kidneys. A buffer is a substance that can reversibly bind hydrogen ions. Limits changes in ph to keep ph constant. In the blood: bicarbonate system lungs, most important aspect of buffering and maintaining blood ph, protein system, phosphate system. In contrast to the kidneys which are a slow process: lungs can affect ph rapidly by changing bicarbonate. Take blood and add different partial pressures of co2 and measure ph and bicarbonate. Normal: partial pressure of co2 is 40 mmhg, ph is 7. 4 and bicarbonate is at 24 mmol/l. If you increase pco2 (drive reaction to the right): ph decreases, bicarbonate goes up. If you decrease pco2 (drive reaction to left: ph increases, bicarbonate decreases.
