CVS pH maintenance Flashcards
What is the equation for pH?
PH = -log10[H+]
What is one unit change in pH equivalent to in hydrogen ion concentration?
one unit change in pH is equivalent to a x10 change in hydrogen ion concentration?
What is the arterial blood pressure?
PH = 7.45
What pH’s are considered acidotic or alkalosis?
Acidotic = 7.35 Alkalosis = 7.45
What happens to potassium levels in the cell when the pH drops and subsequently the H+ ion concentration increases?
A fall in pH means an increase in H+ ions
This causes the bodies cells to exchange hydrogen ions (they move out of the cell) in exchange for potassium ions (these move in)
High levels of potassium in the cell can cause alot of damage.
Typical pH levels in the body?
Cerebrospinal fluid = 7.3
Pancreatic secretions = 8.1
Urine = 5.4
What are the sources in acid / alkali in the body?
Metabolism = typically makes 15 mole of co2 per day
We make 40 mmol of H+ per day
Western die = sees us have an excess of H+
Diet contributes to acid and alkali changes
We lose 10mmol or alkali per day as sodium bicarbonate
There is a net excess of 70 mmol of H+ per day.
What are three ways in which pH in the body is controlled?
Blood and tissue buffers is one method - this takes SECONDS to control pH
Respiration = takes MINITES to regulate co2 levels - it helps you reduce hydrogen ion conc in body. (As in it expels co2)
Renal systems - allows us to extrude alkali or acid from our systems . This takes HOURS or DAYs.
Where are PH buffers found?
They are found in the blood
Extracellular fluid
Intracellular fluid
Urine
Examples of pH buffers in the body?
Haemoglobin
Bicarbonates
Inorganic phosphates
Weak acid/ base proteins
What is the bicarbonate buffer system?
What does this equation mean? Co2 + H20 H2CO3 (carbonic acid) H+ + HCO3
And what happens when we add H+ ions when considering this buffer system?
This buffer system aims to keep the pH of a solution stable
Adding hydrogen to this equation causes the eqm to shift left making more co2 and h20. This co2 increase can be excreted from the body via ventilation. This helps us to maintain our pH in the body.
Its important to note this buffer system goes back and forwards
Using the buffer equation in clinical settings:
Co2 + H20 H2CO3 (carbonic acid) H+ + HCO3
What happens when we have too much co2 to the bloods pH?
What happens when we have too little co2?
An increase in co2 shifts the eqm of the buffer equation to the right
This causes there to be a high bicarbonate and H= ion conc in the situation. You see this in patients
with RESPIRATORY ACIDOSIS, as the increased hydrogen ions lead to more acidic conditions.
TOO little co2?
Eqm shifts left - more co2 and water is made. You may see this with people who have been hyperventilating. They have a RESPIRATORY ALKALOSIS
Where does the bicarbonate buffer system mainly work in conjunction with?
The lungs
Hence why it can stop RESPIRATORY acidosis (when theres too much acid the H+ is converted to co2 and water. This co2 is expelled via the lungs) and why it can stop a RESPIRATORY alkalosis (too much co2 is lost so the body can stop hyperventilating to increase co2 levels)
What is the difference between respiratory and metabolic acidosis?
Respiratory acidosis is when you have a high amount of H+
Metabolic acidosis is when the level of H+ is too low
