Ch 27 Buffers & Acid-Base Balance

What happens to water after adding acid?

turns acidic

What happens to water + buffer after adding acid?

stable pH

What happens to water after adding a base?

turns basic

What happens to water + buffer after adding a base?

stable pH

What is the normal arterial blood pH?

7.4

What if the normal venous blood and IF pH?

7.35

What is the normal ICF pH?

7.0

What pH indicate alkalosis?

pH > 7.45

What pH indicates acidosis?

< 7.35

When pH is = to 7.0-7.35 what is this?

physiological acidosis

What is lower pH due to?

greater amounts of acidic metabolites and CO2, which combines with H2o to form H2CO3

Small amounts of acid are ingested and most H+ originate as?

metabolic by products or end products

Examples of acid base balance?

phosphoric acid released from phosphorus containing proteins into ECF

lactic acid produced via anaerobic respiration of glucose

fatty acids and ketone bodies formed from fat metabolism

CO2 travels as HCO3- in blood liberating H+

Relationship between pH level and H+ concentration is?

inverese

Lower pH = greater of lesser H+ concentration?

greater

High pH = greater or less H+ concentration?

lesser

What do acids do?

release H+ into solution

What do bases do?

remove H+ from solution

How are acids and bases classified?

strong or weak

Strong acids and bases do what?

completely dissociate into its separate ions

Weak acids do what?

release H+ but do not completely dissociate, and keeps releasing until equilibrium is reached to prevent large changes in body fluid pH

Weak base does what?

reduces concentration of H+ by binding to free H+, NH3 + H+ makes NH4

What is a buffer?

solution that prevents extreme changes in pH solution

What do buffers do with body fluids?

stabilize pH by binding xs H+ or by releasgin H+

What maintains pH and is part of 1st line defense for strong acids and bases?

buffers

Strong acids and strong bases result in complete or partial dissociation?

complete

Weak acids result in complete or partial dissociation?

partial until it reaches equilibrium

How is hydrogen ion concentration in blood regualted?

regulated sequentially by chemical buffers, brain stem resppiratory centers, renal mechanisms

What are the 1st line of defense for resist pH changes? How long does it take?

buffers, takes about a second

How do brain stem respiratory centers regulate hydrogen ion concentration?

change RR and depth to compensate for acidosis and alkalosis, take about 1-4min

How do renal mechanisms maintain hydrogen ion concentration in blood?

kidneys most potent regulator, needs hours to at least 1 day

Respiratory and renal mechanisms are considered to be what type of buffering systems?

physiological buffering systems

How do respiratory and renal systems control pH? Do they act fast or slow?

regulate amount of acid or base in the body, but are slower acting compared to chemical buffering but have HUGE buffering potential

What are the 2 major mechanisms for regulating H+ concentration?

chemical buffer systems, physiological buffer systems

How do chemical buffer systems work?

immediately resist pH changes in body fluids

What are the two physiological buffer systems?

respiratory system and renal system

How does the respiratory system act as a physiological buffer system? How long does it take?

short term response to acid-base balance changes, few minutes to correct pH abnormality

How does the renal system act as a physiological buffer system? How long does it take?

long erm, significant response to acid-base balance changes, hours to days to alter body fluid pH

What are the 3 systems together that prevent major changes in pH of body fluids?

carbonic acid/bicarbonate buffer system, protein buffer system, phosphate buffer system

What does the carbonic acid/bicarbonate buffer system use?

ECF buffer

What does the protein buffer system use?

plasma and cells

What does the phosphate buffer system use?

urine and ICF buffer

Why are chemical buffer systems important?

important role in regulation of extracellular pH, limited capacity to resist pH changes

Chemical buffer systems have an essential role in?

control of pH by physiological buffer systems

Chemical buffer systems have a quick response to metabolic conditions such as… (3)

Addition of CO2 or lactate produced by increased metabolism during exercise

Increased fatty acid and ketone body production during times of elevated lipid metabolism

Addition of basic substances (sodium bicarb) intake as antacid

What is the carbonic acid/bicarbonate buffer system?

carbonic acid (H2CO2), is a weak acid formed by CO2 + H2O

What does the carbonic acid/bicarb buffer system depend on?

equilibrium between H2CO3 and H+/HCO3-

What happens when H+ is added to the carbonic acid/bicarb buffer system?

large part binds to the bicarb ion to form carbonic acid and small & remains free, to resist large decrease in pH when acid added to body fluids

What happens when H+ is removed from body fluids for the carbonic/bicarb buffer system?

carbonic acid forms bicarb ion and H+, resists large change in pH when alkaline added to body fluids

What is the protein buffer system?

high concentration of intracellular and plasma proteins act as a large pool of buffer molecules, it is about ¾ body’s buffer capacity, the important buffer is hemoglobin

How does hemoglobin act as a buffer?

due to amino acid functional groups carboxyl/amino groups

How does hemoglobin act as a weak acid and base?

hemoglobin binds H+ and binds to a functional group, when decreased more H+ is released from functional groups

What is the phosphate buffer system?

important intracellular buffer system, phosphate containing molecules in solution that act as buffers

What does the phosphate buffer system do when pH decreases (acidic)?

ions (HPO4-) bind to H+ to make H2PO4-

What does the phopshate buffer system do when pH increases (alkaline)?

opposite, to H2PO4-, H+ is removed, 2 ions fluctuate between gaining and losing H+ to balance pH

How does the respiratory system work as a physiological buffer?

works with carbonic acid/bicarbonate buffer system

When CO2 is produced by cellular respiration what does it react with to maintain pH?

react with water to form H2CO3 to maintain pH, and carbonic acid then dissociates to form H+ and HCO3-

As CO2 increases in the carbonic acid equation what side does the equation move?

equation moves to right to produce more H+ and HCO3-

As CO2 decreases in the carbonic acid equation what side does the equation move?

equation moves to the left to increase carbonic acid and decrease bicarbonate

How does the renal system act as a physiological buffer system?

regulated by renal tubules, the cells change both rate of H+ secretion into filtrate and rate of HCO3- reabsorption

H+ increases when?

pH of body fluid decreases

H+ slows when?

pH increases

Respiratory acidosis and alkalosis are due to?

abnormalities in respiratory system

Metabolic acidosis and alkalosis are due to?

abnormal metabolism

In acidosis what happens?

metabolism makes acidic products that lower pH of body fluids and the body fails to eliminate the acidic products

What is acidosis major effect?

depression of CNS

When blood pH <7.35 what happens?

CNS malfunctions, then causes disorientation then to coma

If there is decreased ventilation what does it lead to?

respiratory acidosis, and increase concentration of CO2 in body fluids

As CO2 levels rise what happens?

there is an increase in H+ concentration which lowest pH of body fluids then the pH is below 7.35 and causes respiratory acidosis

What are causes of respiratory acidosis?

asphyxia, hypoventilation (due to tumor, trauma), severe emphysema, advanced asthma, pneumonia, narcotic OD

How can the body help to resist respiratory acidosis?

buffers and kidneys increase rate of H+ into filtrate and reabsorb HCO3-

Are kidneys effective if respiratory acidosis develops quickly?

no because it takes 1-2 days to become maximally functional

What can cause respiratory acidosis to develop quickly?

asthma attack

What can cause respiratory acidosis to slowly occur?

emphysema (COPD)

Kidneys are effective in respiratory acidosis when?

when it develops slowly or lasts long

What is metabolic acidosis due to?

due to all conditions that decrease pH of body fluids <7.35 except for a few respiratory conditions

What can cause metabolic acidosis?

xs EtOH, severe diarrhea, vomiting, untreated DM

How does untreated DM cause metabolic acidosis?

body metabolizes lipid store for energy which can create acidic metabolites and cause pH of the body to drop

H+ accumulates in body fluids and the buffer tries to compensate

What happens in untreated DM if buffers are unable to regulate body pH?

respiratory center tries to help, and tries to increase breaths to cause hypoerventilation to eliminate CO2 at a faster rate to maintain pH

If metabolic acidosis is persistent for hours and kidneys are functional what occurs?

kidneys help compensate by secreting H+ at a greater rate and increasing rate of HCO3- reabsorption

Symptoms of metabolic acidosis appear when/

appear if respiratory and renal systems do not maintain pH of body fluids within normal range

What is alkalosis due to?

xs elimination of acidic products of metabolism

What can alkalosis lead to>

muscle spasms, tetany, convulsions which can cause death

What is respiratory alkalosis due to?

hyperventilation because it eliminates xs CO2 from the body, cause decrease of H+ levels >7.45 to cause respiratory alkalosis

Causes of respiratory alkalosis?

hyperventilation, brain tumor or injury

During respiratory alkalosis how do kidneys help compensate?

kidneys decrease rate of H+ secretino into filtrate and rate of HCO3-

If pH increases how long does it take kidneys to compensate?

1-2 days

If hyperventilation is triggered by emotions can it resolve quickly?

yes, so no respiratory alkalosis occurs

If someone is at a high altitude for 2-3 days can it resolve on its own?

no, kidneys need to compensate

What is metabolic alkalosis due to?

due to all conditions that increase pH of body fluids >7.45, except those that alter function of respiratory system

As H+ decreases in body fluids buffers initially resist pH, if buffers are unable to compensate what tries to regulate body fluid?

respiratory system tries to regulate, followed by the renal system

Increased pH inhibits?

respiration

What does less respiration allow?

allows CO2 to accumulate the body fluids which lowers pH

Causes of metabolic alkalosis?

severe vomiting, consuming large amounts of NaHCO3 in diet, constipation

>7.0 in blood pH can cause?

CNS depression, coma, death

>7.8 blood pH can cause?

nervous system overexcites and causes tetany, convulsions/ xs nervousness and death by respiratory arrest