Acid Base
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Define pH
A measure of the molar concentration of hydrogen ions in solution pH = -log10 [H+]
What is increasing H+ concentration responsible for
Increasing acidity
What is increasing OH- concentration responsible for?
Increasing basicity
What are the two ley properties of the pH system?
As pH decreases the [H+] increases The pH scale is a log scale, it is not linear
What is the pH reference range for plasma?
7.35 to 7.45
What is the H+ reference range for plasma
35-45 nmol/L
Why is acid base balance needed? (3)
There is always production of acid by the body’s metabolic processes To maintain balance, these acids need to be excreted or metabolised The various acids produced by the body are classified as respiratory/volatile acids and as metabolic/fixed acids
How are acids produced by the body classified
Respiratory/volatile acids Metabolic/fixed acids
What is acidosis? (3)
pH below the normal range Trying to push your pH into an acid range Less than 7.35
What is alkalosis (3)
pH above the normal range Trying to push your pH into alkaline range pH greater than 7.45
What two organs have roles in maintaining acid-base balance
Kidneys Lungs
How do the kidneys regulate acid base balance (2)
They regulate hydrogen ion concentration They generate and recycle buffers that enter the bloodstream
How do the lungs regulate acid base balance
Eliminate carbon dioxide which is acidic
What is considered acidaemia
Blood pH less than 7.35
What is considered alkalaemia?
Blood pH greater than 7.45
How is carbon dioxide broken down? (3)
CO2 (acid) + H2O Converted to H2CO3 (Carbonic Acid) Converted to H+ + HCO3- (bicarbonate ion)(base)
What molecule is acidic?
CO2
What molecule is basic
HCO3-
Why is carbon dioxide so important in acid-base balance? (3)
Regulation of the amount of CO2 in blood, or more precisely the ratio of bicarbonate to dissolved carbon dioxide concentration is essential for maintaining acid-base balance CO2 is a major determinant of blood pH because of it’s conversion to carbonic acid As CO2 concentration rises, so does H+ concentration
What is pCO2?
Partial pressure of Carbon dioxide
What controls respiration rate? (2)
pCO2 sensitive chemoreceptors in the brain stem and carotid artery Respiration rate is increased if pCO2 is rising and decreased if PCO2 is declining
How does increased respiratory rate affect CO2 concentration
This increases the rate of CO2 elimination
How does decreased respiratory rate affect CO2
This promotes CO2 retention
What might a low CO2 be associated with (2)
Metabolic acidosis Compensated respiratory alkalosis