Exam 3 patho: Acid-Base balance

Disassociate

Separation of molecules into 2+ simpler fragments in order to participate in another rxn

Carbonic anhydrase (CA)

an enzyme that catalyzes the hydration of carbon dioxide (CO2) to make carbonic acid (H2CO3)

• found in RBCs and renal tubular cells

Carbonic acid

H2O + CO2 —> H2CO3

• basically CO2 dissolved in H2O

• Acid

Bicarbonate (HCO3-)

A base that is used as a buffer system to change the pH of the blood

Bicarbonate buffer system

• Uses H2CO3 (carbonic acid) & bicarbonate salt (NaHCO3)

• Substitution occurs (weak acid or weak base substituted for strong ones)

Purpose of buffer systems and how do they work?

• maintains the pH balance in the blood and other bodily fluids

• It works by neutralizing excess acids or bases, ensuring that the blood pH remains within the narrow range necessary for proper physiological function.

Acids

molecules that can dissociate and release H+

• example: HCl dissociates in water to form H+ and Cl-

(I dont get it) Volatile byproducts of a metabolic process

• Carbonic acid is in equilibrium with CO2

• Easily evaporates and can be eliminated by the lungs

  • Example: carbonic acid will release CO2 through exhalation

    • Method of CO2 being carried through BS

(I dont get it) Non-volatile byproducts of a metabolic process

• Occurs from metabolism of dietary proteins, carbs, and fats

  • Oxidation produces HCL, sulfuric acid, phosphoric acid

  • Incomplete oxidation

    • Glucose results in lactic acid

    • Fats produce ketoacids

• Eliminated by kidneys after being buffered

Base

ion/molecule that can accept an H+

• Example: HCO3- can accept H+ to form H2CO3

Sources of bases (2) from metabolism and types of each

• Metabolism of amino acids

  • aspartate, glutamate

• Metabolism of organic anions

  • citrate, lactate, acetate

What are the 3 buffer systems the body can use to respond to changes in pH?

• Chemical

• Respiratory

• Renal

Normal body pH

7.35-7.45

Chemical buffer systems function

prevent big swings in pH by using moment-to-moment pH adjustments

• Most common

What are the 3 types of chemical buffer systems?

• Bicarbonate buffer system

• Transcellular H+/K+ exchange

• Bone

How does the bicarbonate chemical buffer systems work?

Uses substitutions of a weak acid for a strong acid, or a weak base for a strong base

• allows for easier addition or removal from body

The chemical buffer system is a method of ______ for ions

substitution

Example of substitution when expelling CO2

HCl + NaHCO3 —> H2CO3 + NaCl

• H2CO3: can be taken to lungs and expel CO2

• NaCl: body can easily take this up

Transcellular H+/K+ exchange chemical buffer systems

Regulating the movement of hydrogen (H+) and potassium (K+) ions across cell membranes to maintain pH

• If H+ is high in blood, H+ taken out of BS and put inside cell

  • This will then decrease the amount of acid in the BS

  • K+ is now in the BS — if this happens too much, this can result in too much K+ in the BS

Bone chemical buffer system

H+ extracellular ions can be exchanged for ions in the bone to decrease pH

• bone will help buffer the acidic ECF

• H+ will dissolve in bone tissue

What is the mechanism of action for bone chemical buffer systems?

H+ will dissolve in bone tissue, which will release sodium bicarbonate (NaHCO3) and calcium carbonate (CaCO3) into the ECF

• this helps buffer the excess acids in the BS

CO2 transport Methods (3)

• As CO2

• As a bicarbonate ion

• Carbahemoglobin

Protein buffers?? Slide 14 — look in patho book for explanation

Respiratory control for pH balance

Regulates CO2 levels by changes in respiratory rate by sensing CO2 levels through chemoreceptors in the brainstem and periphery

• Can be stimulated within minutes

• Does not completely correct acid-base in lungs (lasts 24-48 hrs)

How does changing respiratory rate impact pH?

Chemoreceptors in brainstem and periphery

• Hyperventilate = get rid of CO2 = increase pH (more alkaline)

• Hypoventilate = hold onto CO2 = decrease pH (more acidic)

How does respiration regulate CO2 and therefore pH?

H2CO3 —> CO2 + H2O

• More CO2 present = more acidic

• H2O and CO2 can combine to increase pH/decrease acidity

Renal control mechanisms

Regulating the levels of H+ and bicarbonate in the blood

• most effective

• Takes the longest

What are the 3 renal control mechanisms?

• H+/HCO3 exchange — CA catalyst

• Distal renal tubule regulates acid-base balance

• Transcellular H+/K+ exchange

GO BACK TO THE RENAL CONTROLS — DO NOT UNDERSTAND!!!

**Kidney has the ability to pull ions back into the ______ cells to eliminate excess _____

• Tubular cells

• Acid

What does the distal renal tubule regulate?

Acid-base balance

How does the distal renal tubule regulate acid-base balance?

Reabsorb HCO3 from urine

H+/HCO3 exchange

• CA catalyst used to combine

• H+ + HCO3- —> H2CO3 —> CO2 + H2O

When CA is inside the tubular cell, what will form?

H2CO3 —> HCO3- + H+

What is released from the nephrons to act as a buffer to increase the blood pH?

HCO3- is used to increase pH

H+ is released into the urine filtrate

Role of distal renal tubule

Reabsorb HCO3- from urine

What forms H2CO3? What does H2CO3 dissociate into to decrease blood pH?

• Intracellular carbonic anhydrase makes H2CO3

• H2CO3 —> HCO3- + H+

HCO3- and H+ are the end product of the distil renal tubule mechanism. What is the end result of this?

• HCO3- goes into the ECF and acts as a buffer (base)

• H+ is eliminated in the urine

• This results in decreased pH

What is the purpose of carbonic anhydrase?

speeds up the exchange of ions and the speed of HCO3- and H+ production

What will the kidney excrete that addresses alkalosis? What is the result of this?

the kidney will make the bicarbonate exit via excretion to prevent blood from getting more basic

• this results in increased K+ in the kidney

Phosphate (PO4-) and Ammonia (NH3) Buffers

• Phosphate and ammonia will buffer the H+ ions

  • Helps bring down acid levels in our body

  • Allows acid to be excreted in the body, which CANNOT be pulled back into the tubules cell and will

    remain in the urine filtrate

Phosphate (HPO4-) mechanism

1. HPO4- binds with H+ ion

2. forms a lipid molecule (H2PO4), making it lipid soluble

3. this means it cannot be pulled back into the into the tubule and must be excreted through the urine

Ammonia (NH3) mechanism

1. Diminishing AAs produces NH3, which is excreted out into the urine filtrate

2. NH3 meets H+ and becomes NH4+

3. NH4+ does not come back into the tubular cells

ROME

R: Respiratory

O: Opposite (pH is opposite of CO2 levels)

M: Metabolic

E: Equal (pH is equal with HCO3-)

Normal pH in body

Metabolic acidosis pH and HCO3 levels increase or decrease?

• Decreased pH

• Decreased HCO3-

Causes of metabolic acidosis (4)

• Production of metabolic acids

• Decreased renal function

• Increased bicarbonate losses

• Hypercholermic acidosis

What can result from the production of metabolic acids?

• Acute lactic acidosis

• Ketoacidosis

Acute lactic acidosis

when there is a buildup of lactic acid in the bloodstream, leading to a dangerous drop in the body's pH

Ketoacidosis

high levels of blood acids called ketones build up

How does decreased renal function cause acidosis?

When kidney can’t get rid of H+ and can’t reproduce bicarbonate

How does decreased bicarbonate result in acidosis?

Bicarbonate works to decrease pH, so an absence will prevent pH from being increased

What symptoms may occur due to bicarbonate losses? (2)

• Diarrhea

• Fistulas

  • Ileostomies may be needed

Hypercholermic acidosis

Abnormal absorption of chloride ions

• pH is lowered due to an increase in chloride levels, leading to an excess of acid

Will urine be acidic or alkaline with metabolic acidosis?

Acidic because kidneys are getting rid of H+ and NH4+

Metabolic alkadosis

Excess base in the blood

Does pH and HCO- increase or decrease during metabolic alkalosis?

• pH increases

• HCO- increases

Causes of Metabolic Acidosis

• Excess Base Loading

• Loss of fixed acid

• Fluid depletion (bc of the above stuff)

Excess base loading examples (too much base in your body)

• Over ingestion of antacids (too many tums)

• IV infusion excess (giving someone to much base)

• Milk-alkai syndrome

How can we lose fixed acid that results in alkalosis? (4)

• Vomiting

• GI suction

• Bulimia

• Diuretics

How is metabolic alkalosis compensated for?

Hypoventilation

Respiratory acidosis

the lungs can't remove enough carbon dioxide (CO2), causing the blood and body fluids to become too acidic

Does pH and PCO2 increase or decrease during respiratory acidosis?

• pH decreases

• PCO2 increases

Causes of respiratory acidosis

• Acute — rapid increase in CO2 (ex: can’t take a deep breath)

• Chronic — COPD

• Increased CO2 production — can occur with fever + sepsis

Compensation for respiratory acidosis

Acid in urine

• Issues with respiratory system, we cannot compensate with breathing unless provided an O2 mask

Respiratory alkalosis

the blood pH is elevated due to low levels of carbon dioxide (CO2) in the blood

• This typically occurs because of hyperventilation

Does pH and PCO2 increase or decrease during respiratory alkalosis?

• pH increases

• CO2 decreases

Cause of respiratory alkalosis

Hyperventilation

• central stimulation of medullary center of brain

• Mechanical ventilation

• Hyperventilation syndrome

Types of central stimulation of medullary center of brain

• Pain

• Pregnancy

• Sepsis/febrile states

• Encephalitis/TBI

How is respiratory alkalosis compensated for?

Alkalne urine