Acid-Base Balance

Portage Learning BIOD 152, Mod. 7

the fluid inside the cells

• accounts for about 60% of the fluid in the body

intracellular fluid

fluid found outside of the cells

• accounts for about 40% of the fluid in the body

• consists of two sections: plasma and interstitial fluid

extracellular fluid

the fluid portion of the blood that contains about 8% of total body water

plasma

the fluid in the microscopic spaces between cells that contains about 32% of total body water

institial fluid

the balance of the concentration of hydrogen ions in the blood

• the pH scale ranges from

acid-base (pH) balance, 0-14

the pH of 0 is the most _

the pH of 7 is the most _

pH of 14 is the most _

• The higher concentration of H+ ions present in a solution means it is more acidic

• When strong acids are dissolved in water, they produce hydrogen ions, making the solution more acidic and lowering the pH

• when bases are dissolved in water, OH is produced, which combines with H+ ions. the combination of OH- and H+ removes the hydrogen ion so it is no longer active in the solution, becoming more alkaline

acidic, neutral, alkaline (basic)

all proteins are dependent on a narrow range of Ph in the fluid in which they function

• maintaining a constant Ph is particularly important for _

  • specialized proteins that control the rate of all metabolic reactions

enzymes

the normal pH of arterial blood is between 7.35-7.45, if pH rises above, the condition is called _, because pH is more alkaline than normal

if arterial blood drops below 7.35, the condition is called _, becauise this pH is more acidic than normal

alkalosis, acidosis

venous blood and interstitial fluid have a lower (more acidic) pH because of the acidic materials

• chemical reactions inside a cell to maintian life is the principal method through which acids enter the human body

  • the blood acidity is controleld by three main methods:

cellular metabolism

chemical buffer systems, the brain stem respiratory center, the renal system

a negatively charged ion, for example, the bicarbonate ion (HCO³)

anion

a positvely charged ion, such as ammonium (NH^4+)

cation

the pairing of anions and cations minimizes _ by binding with free H+ ions, the other substance reacts with oH- to bind it, therefore preventing it from raising the pH

pH changes

a major chemical buffer system, fast-acting

• acts as the main buffer of the interstitial and plasma fluids

• composed of the weak carbonic acid (H2CO3) and the bicarbonate ion (HCO3)

bicarbonate system

a major chemical buffer system, fast-acting

• acts as one of the buffers in the urine and the intracellular fluid

• composed of the weak acid (H2PO4) and monohydrogen phosphate ion (HPO4^-2)

phosphate system

a major chemical buffer system, fast-acting

• the main buffer of the intracellular fluid

• provides three times the buffering capacity of all the other systems combined due to the substantial concentration of proteins inside cells

• includes amino acids, hemoglobin and plasma proteins

protein system

carbon dioxide is removed from the blood and oxygen is added to the blood

• has chemoreceptors in the medulla of the brain stem that monitor the level of CO2 in the blood

• in the red blood cells, CO2 reacts reversibly with water to form _

  • this dissociates when dissolved in water to form H+ and _

    • This is the form in which CO2 is transported in the blood plasma

respiratory center, carbonic acid, bicarbonate ions

reaction regulated by the respiratory center to maintain pH

CO2 + H2O ←> H2CO3 ←> H+ + HCO3-

if blood Ph begins to fall (acidic) the respiratory center is excited causing this

• is an increase in the respiratory rate, helping to remove additional CO2

  • removing CO2 uses up H+, causes the PH to rise (basic) and restores correct bood Ph

hyperventilation

if blood pH begins to rise (alkaline), the respiratory center is depressed

• the respiratory rate slows down, allowing more CO2 to accumulate

  • forming more hydrogen ions, the pH falls (acidic) and restores correct blood pH

• respiratory center malfunctions that lead to Ph imbalances are called _ (CO2 retention) and _ (CO2 removal)

hypoventilation

respiratory acidosis, respiratory alkalosis

is a much slower-acting, taking hours to days to have an effect

• have a much larger impact on the pH level, is the major system used to manage acid-base imbalance caused by daily metabolic processes or abnormal disease conditions

• The major way is by excreting or reabsorbing the bicarbonate ion

• acid-base balance depends on H+ ion secretion and the conversion of bicarbonate

  • H+ secretion occurs in response to the pH of the extracellular fluid, the capillaries are tiny blood vessels that travel alongside the nephrons, allowing reabsorption and secretion between blood and the nephron

  • the conservation of bicarbonate, which can be replenished in the plasma by reclaiming it from the renal filtrate

  • during alkalosis, intercalated cells can secrete bicarbonate while simultaneously recovering H+ to lower the pH of blood

renal control mechanisms

disorders are classified as metabolic or respiratory depending on whether the cause is higher or lower CO2 pressure (respiratory) or other cellular processes in hte body (metabolic)

• in severe _, pH drops below 7.0 and the CNS is markedly depresses causing coma and imminent death

• in severe _, blood pH rises above 7.8 and the nervous system is markedly excited causing extreme nervousness, muscle contraction, convulsion, and death due to cessation of breathing

acidosis, alkalosis

characterized by lower pH because of a higher CO2 pressure

• is caused by shallow breathing or limited gas exchange

  • diseases such as cystic fibrosis, emphysema or pneumonia limit gas exchange and increase the amount of CO2 in the blood

  • causes the renal system to attempt to correct the disorder through renal compensation

respiratory acidosis

characterized by higher pH because of lower CO2 pressure

• is almost always caused by hyperventilation (over-breathing), such as in a panic attack

• causes the renal system to attempt to correct the disorder through renal compensation

respiratory alkalosis

characterized by lower pH (with normal CO2 levels) because of lower HCO3 concentration

• causes a buildup of acidic metabolic products such as acetic acid (alcohol overdose), lactic acid, diabetic ketosis, or extreme diarrhea

• The respiraotry system works to correct through respiratory compensation

metabolic acidosis

characterized by a higher pH (with normal CO2 levels) because of higher HCO3 concentration

• caused by vomiting, intake of excess antacids, and constipation

• The respiratory system works to correct through respiratory compensation

metabolic alkalosis

normal blood serum levels

normal pH:

normal PCO2:

normal HCO3:

7.35-7.45

35-45 mm

22-26 mEq/:

abnormal PCO2 levels (mm)

normal: 35-45

respiratory acidosis: > 45 (if causing condition, increased kidney retention of HCO3)

respiratory alkalosis: < 35 (if causing condition, decreased kidney retention of HCO3)

abnormal HCO3 levels (mEq/L)

normal: 22-26

metabolic acidosis: < 22 (if causing condition: hyperventilation)

metabolic alkalosis: > 26 (if causing condition: hypoventilation)