Module 5 Flashcards
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
