What are the acids of the body
- hydrogen containing substances disassociate into H+ and anions
- many substacnes contain H but are not acidic
- Disaasociation is when there is too much in the water that it dissassociates in amounts realtive to its strength
- The more H that dissassociates, the stronger the acid is , the less is the weaker
What are the bases of the body
- Substances that bind to free H and remove it from the solution
- strong/weak acids and bases
- Bases will dissaociate to OH and Na, this decreases the concentration of free H- as the OH binds to any free H+ to form water
Give a basic overview of acidosis and alkalosis in the body
- pH of arterial blood is 7.45
- pH of venous blood is 7.35
- Average of these two values is 7.4
- Acidosis exits whenever blood pH falls below 7.35 and alkalosis occurs when pH rises above 7.45
- Severe changes in pH are not compatible with life
- pH less than 6.8 and greater than 8 will result in death
What are the main effects of acidosis and alkalosis
- Acidosis supresses the CNS
- early symptoms are disorientation
- Can rapidly lead to death and coma
- Alkslosis leads to over excitability of CNS and PNS
- Extreme alkalosis is caused by the death of spasm of the respiratory muscles or from convulsion
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* Most enzymes are optimzed for pH of 7.4
* pH can speed or slow reactions
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Changes in H can lead to change in the amount of K in body fluids
blood is more acidotic then more H and K will be secreted
* if blood is more acidic than basic more H than K will be secreted
* Increases the plasma K
* K causes cells to depolarize and become more exciteable
Where is H produced in the body
- Mostlt comes form metabolic sources
Carbonic acid formation - by products of cellular respiratorion is CO2 and H2O
- COnverted to H2CO3
- then into H and bicarbonate
- reactions is reversibke
- in lungs where CO2 is remobed, the reaction backwards removes H
- Respiration will balance metabolic acitivity
**Inorganic acids produced from the breakdown of nurtrients **
* dietary proteins contain S and P
* broken down to make S and P acids
* both are strong
* Vegetables and fruits produce more bases athan acids
* counter the H formed in protein metabolism
* PRotein rich diets, an excess of H is produced
Organic acids from intemreidary metabolism
* fatty acids produced during fat metabolism and lactic acid produced in muscles
* It is weak they will dissassociate to contribute to the pool of H
What is the H2CO3 HCO3 buffer pair
- H2CO3 == HCO2 + H
- when base is added to a solution with this buffer
- base will bind to the free H
- reaction moves forward
- so more H dissassociates
- opposite is also true
- when acid is added to the solution, the reaction will move in the backwards direction so less H dissaossicates
- see diagrams
- Most imrpotant buffer un the human body responsible for buffering pH changes from everything other than Co2 generated by H2CO2
- effective for 2 reasons
- H2CO3 and HCO3 are present in high quantiuties of the ECF
- they have a high capacity for buffering changes in pH
- Highly regulated in the body to keep their concentrations relatively stable
- Kidneys regulate HCO3 while respiratory systems regulate H2CO2 by regulating CO2
WHat is the protein buffer systems
- Very good amino acid buffers
- Amino acids contain basic and acidic groups
- They give up H respectively
- dont play a significant role compared to the H2CO3 system
What is the hemoglobin buffer systems
- essential buffer of H generated from metabolically produced CO2 without ptoduced Co2
- without this systems, veous blood becomes acidic
**CO2 in plasma **
* as CO2 leaves tissues and enters blood
* most forms H2CO3 in RBC with help from enzyme carboni anhydrase
O2 in plasma
* Most H immediately binds to hemoglobin and no longer adds to the acifity
* This freees up O2 that can be released to the tissues
HCO3 in plasma
* Some H2CO3 will immediately dissassociate into HCO and H
What is the phosphate buffer systems
- Uses acud phosphate sakt that can donate H when H falls or accept H when increases
- Concentration of the acid phosphate salt is very low in ECF
- does not play a major role
- Buiffers the pH of urine
- diet is rich in phosphate
- excess ohosphate is filtered bu the kidneys
- Plays an important role in cells only because concentrations of phosphate are higher
- **This is the only buffer present in urine **
How do chemical buffers acts as the first line of defence
- chem reactions occur fast
- buffers are quick to remove H from body fluids but have a limited capapcity to reabsrob H
- They cannot constantly face the addition of protons without being overwhelmed
- They are effective until the repsiratory and renal systems remove them
How does the respiratory system respond to H
- CO2 leads to H generation
- Pulmonary ventillation can increase or decrease to remove CO2
- Arterial H is the primary determinant of respiratory activity
Unbuffered solution
* When arterial H rises from non respiratory sources
* the brain stem is stimmed to increase pulmonary ventillation
* removal of CO2 means less H2CO3 and less HCO3 and H
Buffered solution
* when arterial H decreases
* pulmonary ventillation reduces
* slower shallower breathing decreases the blood exhalation of CO2 and allows it to accumulate in the blood
* Excess CO2 means more H2CO3, more H and more HCO3
- Respiratory system removes 100x more CO2 than the kidneys
- second line of defence
- not as efficient because no chemical buffers
- respiratory buffer can only return pH to 50% of what is was towards normal levels
What are kidneys and teh acid base balance
- Effective at preventing free H from contributing to the fluid pH
- Not the same as removing H from the body fluids
- not effective enough to remove all the H from metabolic sources
Important for - Excretion of H
- Excretion/reabsortopn of HCO3
- secretion of ammonia
What is the renal secretion of H
- all excess H is excreted in urine
- comes from plasma at pH 7.4 in the prox, distal and collecting tubules
- H is very low
- Little H is actually filtered
- Because the secretion of urine is acidic pH is 6.0
steps
* CO2 enters the tubular cells from plasma to tubular fluid
* within the cells, CO2 and H2O under the influence of intracellular carbonic anhydrase form H2CO2 which disaassociates in H and HCO3
* energy dependnt carrier on the luminal membrane will then transport H into the tubular fluid
How is the rate of H secretion controlled
- related to acid-base status of the ECF
- no neural or hormonal control
- Tubular cells increase the secretion of H
- when plasma is decrease , the tubular cells decrease the secretion of H
- when the plasma CO2 rises more H is secreted while less H is secreted
- When plasma CO2 decreases
- Bc of dual regulation, the kidnets are able to adjust H secretion from both carbonic and non carbonic acid sources
Describe the reabsorption of filtered HCO3
- acid-base imbalance
- kidneys regulate plasma in 2 ways
- Reabsorptopn back into plasma and addition of new HCO3 to the plasma
- HCO3 is freely filterable
- Luminal memvranes are impermeable to HCO3 so reabsorption is indirect
Steps
* HCO3 in the tubular fluid combines with secreted H to create H2CO3 which is broken down into water and CO2
* it can freely cross into luminal membranes
* Once inside, carbonic anhydrase converts it back to H2CO3 which freely disaasociates into HCO3 and H
* HCO3 can cross the basolateral membrane, leaves the cell and H is secreted, a greater mount of H is secreted than HCO3 from filtered
* All of the filtered HCO3 is normally reabsorbed as H and is available to combine with it and form the highly absorbtive CO2
What are the urinary buffers
- Body produces excess H
- limits to H excretedi n the tubular fluid
- cells secrete H until tubular pH is 4.5
- after it cannot secrete more
- urinary buffers remove free H from the tubular fluid so it doesnt contibtribute to tubular acidity
Phosphate
* dietary phosphate freely filtered for elimination
* Once tubular fluid and H that is buffers will be excreted from the body
* primary purpose of basic phosphate is to remove excess
* does not regulate the amount of phosphate added ott he tubular fluid
Ammonia
* Under acidic conditions
* When phosphate buffer has be maxed
* Tubular cells secreted NH3 into tubular fluid
* Reacts with H to form NH4
* Is not reabrobed and is then secreted un the urine
* Secreted and synthezied bu tubular cells proportionally to the amount of excess H
What are acid-base disorders
- ratio of HCO3 to CO2 is normally 20:1
- this makest he pH 7.4
Change in pH - caused by respiratory system will have abnormal CO2 change in CO3 generated H
- change in pH caused from metabolism will have abnormal HCO from inequality in the amount of HCO3
- HCO must buffer
Change in 20:1 ratio
* When falls below causes acidosis as the pH will be less than 7.4
* when it rise above it causes alkalosis as the pH will be greater than 7.4
What is respiratory acidosis
- caused by buildup of CO2 in plasma
- ratio falls below 20:1
- cause by hypoventillation
- Less CO2 is removed
- Caused by emphysema, chronic bronchitis, asthma, pneumonia, and acidosis
Uncompensated
* Increase in CO2
* Leads to the formation of H and HCO
* leads to acidosis yet there is little change in HCO
* Modest increase in CO2 can lead to acidosis since it is 60000x greater than H.
Compenseated
* to compensate for respiratory buffers start taking extra H and kidneys secrete more H while absorbing HCO3
* even if CO2 remains high the body will contineu to compensate until HCO3 elevates enough to restore the ratio of 20:1
* Respiratory system cannot play a role in compensation as it caused by respiratory failure in the first place
What is respiratory alkalosis
Uncompensated
* Decrease in CO2
* Increase in the ratio since there is little change in HCO3 which results in increased pH
Compensated
* Chemical buffer system releases H and the respiratory system responds by decreasing vebtillaton
* CO2 and H are the driving forces behind increased ventillation so when they decrease the respiratory center decreases ventillation
* Kidneys decrease H secretion and increase HCO2
* when fully compensated, HCO3 is reduced to restore the HCO CO2 ratio
What is metabolic acidosis
- Known as respiratory acidosis
- anything that causes acidosis beside an excess of CO2
- caused by decrease in HCO3
- can be the excessive loss of it
- could be from the buildup of non carbonic aids whihc also decrease HCO3 from buffering
*
What are the different anion gaps
Low anion gap
* Uncommon and generally results form the loss of plasma albumin such as during a haemmorage
Normal anion gap
* Loss of HCO3
* caused by diarrhea
* and some renal diseases
* Generally compensatory increase in Cl to conserve electricla neutrality
High anion gap
* Metabolic acidosis
* Increase in unmeasured anions
* Decrease un HCO3
* Used for buffering acids
What is the compensation for metabolic acidosis
Uncompensated
* Decrease caused by excessive loss of HCO3 from the buildup of non carbonic acids
* also decrease HCO3 due to buffering
Compensated
* all except acidosis
* Occurs by the buffers taking up extra H
* Lungs blowing off extra CO and the kidneys secreting more H and conserving HCO3
* Respiratory system can only partially compensate for metabolic acidosis
* SOmeone with uraemic acidosis cannot fully compensate
* Metabolic acidosis due to decrease in kidney function
What are causes of metabolic acidosis
Severe diarrhea
* digestive juices are rich in HCO3
* HCO3 may be eliminated before it can be reabsorbed
* causes a drop in HCO
* Decreasing the buffer capacity of the plasma
Diabetes
* Without insulin
* Glucose does not enter most cells
* Revert to fat metabolism to generate ATP
* Causes an increase in keto acids which raise the anion gap
Strenous exercise
* Muscles resort to anaerobic metablosm
* excess lactate produced which raise plasma H
* also raise anion gap
Uraemic acidosis
* Renal failure
* Kidneys cannot excrete excess H
* H increased and generally a loss of HCO3 as well as increased anion gap
