Acid Base Hemostasis Flashcards
The body maintain [H+] at about ______
The primary organs of acid base homeostasis are the Kidneys and the Lungs
40nmol/L
Whys is more common for acidosis to occur instead of alkalosis
The body tends to produce H+ ion rather than Oh-
Plasma [HCO3] is controlled mainly by the kidney
PCO₂ is controlled mainly by the lungs
Metabolic abnormalities are corrected by adjusting the ____&& and compensation is usually immediate but incomplete
Respiratory disorders are corrected by adjusting the ____&&
respiratory system
renal system
_______is the most important buffer system of the ECF compartment
pKa = 6.1
Bicarbonate Buffer system
Buffering is a temporary measure and the H+ must be removed or eliminated from the body
H+ can be removed from the body only through the Kidney and the GIT
Conversion and Transportation:
Most CO₂ is expelled by the lungs. Some CO₂ is converted into bicarbonate (HCO₃) by renal tubular cells (RTCs) and red blood cells (RBCs).
Diffusion and Exhalation:
CO₂ moves from the tissues into the extracellular fluid (ECF) and then into the alveolar spaces in the lungs, from where it is exhaled.
The body aims to maintain a partial pressure of CO₂ (PCO₂) around
5.3 kPa.
Where’s Carbonic Anhydrase (CA) located and it’s function
The CA enzyme facilitates the following reaction: CO2+H2O↔H2CO3↔H++HCO3−\text{CO}_2 + \text{H}_2\text{O} \leftrightarrow \text{H}_2\text{CO}_3 \leftrightarrow \text{H}^+ + \text{HCO}_3^-CO2+H2O↔H2CO3↔H++HCO3−
This reaction is key to producing bicarbonate (HCO₃⁻), which helps regulate the body’s pH levels.
CA is an enzyme found mainly in renal tubular cells (RTCs), red blood cells (RBCs), and certain eye cells.
It helps maintain intraocular pressure in the eyes and is crucial for maintaining the body’s acid-base balance.
Bicarbonate production increases when:
CO₂ levels rise.
HCO₃⁻ levels fall.
H⁺ levels fall because H⁺ is either buffered by hemoglobin (Hb) or excreted by the kidneys
For a normal person the partial pressure of
Co2 is
Hco3
Ratio of hco3 to co2 in ecf is?
Partial pressure of CO₂ (pCO₂) is about 5.3 kPa.
Bicarbonate concentration [HCO₃⁻] is about 25 mmol/L.
The ratio of [HCO₃⁻] to [CO₂] in the extracellular fluid (ECF) is approximately 20:1.
This ratio corresponds to a pH of about 7.4, with a pKa of 6.1.
Inside RBCs, H⁺ is buffered by ____
Hb, and HCO₃⁻ diffuses out
Inside RBCs, H⁺ is buffered by Hb, and HCO₃⁻ diffuses out.
Electrochemical neutrality is maintained by the “chloride shift” (exchange of bicarbonate and chloride ions).
RBCs are like transport trucks that don’t use the factory’s fuel (oxygen) but carry CA machines to convert CO₂ into bicarbonate on the go. They also have plenty of water and handle CO₂ efficiently. Hemoglobin in RBCs acts like a sponge, soaking up excess hydrogen ions, while bicarbonate is swapped for chloride ions to maintain balance.
Electrochemical neutrality is maintained by the “chloride shift” (exchange of bicarbonate and chloride ions).
What’s the Role of Carbonic Anhydrase (CA) in the Kidneys:
Renal tubular cells (RTCs) have a lot of CA, an enzyme that helps regulate bicarbonate (HCO₃⁻) levels in the extracellular fluid (ECF).
What are the Steps of Bicarbonate Reclamation:
Bicarbonate and sodium are filtered by the kidneys.
Sodium is exchanged for H+ in the kidney cells.
Bicarbonate combines with H+ to form carbonic acid, which then breaks down into water and CO₂.
CO₂ diffuses back into the RTCs and forms carbonic acid again with water, catalyzed by CA.
This carbonic acid then breaks down into bicarbonate and H+, repeating the cycle.
Bicarbonate Reclamation:
The kidneys reclaim or reabsorb bicarbonate to maintain a steady state, preventing any net loss of H+.
Bicarbonate from the blood is filtered by the kidneys and reabsorbed through a process involving CA.
However, this process alone cannot correct acidosis (excess acidity in the blood
Explain Bicarbonate Generation:
Similar to bicarbonate reclamation but occurs after all filtered bicarbonate has been reclaimed.
CO₂ for this process comes from cellular reactions within RTCs.
Results in net generation of bicarbonate and elimination of H+.
This process is important for correcting acidosis and depends on the availability of buffer bases.
What are the other buffer systems
Phosphate buffer system
Ammonia buffer system
Gastrointestinal Tract (GIT) and Acid-Base Homeostasis:
Phosphate buffer & Ammonia buffer system is effective when the ph is?
____&____
Ph–effective @7.4
Less effective @5.5
Ammonia effective @ 5.5
