Renal Mechanism of Acid Base Balance

Question 1

Acid-Base Balance

• Acid-base balance is one of the most important of the body’s _______ mechanisms
• Acid-base balance refers to regulation of __________ ion concentration in body fluids
• Precise regulation of ___ at the cellular level is necessary for survival
• Slight pH changes have dramatic effects on cellular metabolism

Answer 1

homeostatic

hydrogen

pH

Question 2

Acid-Base Balance

• Achieved by:
– Utilization of chemical buffers in ECF & ICF
– Respiratory mechanisms that excrete ____
– Renal mechanisms that reabsorb ___________ and secrete hydrogen ions
• Normal range of arterial pH is____-_______

Answer 2

CO2

bicarbonate

7.37 – 7.42

Question 3

Acid Production in the Body

• CO2 - end-product of aerobic metabolism; ___________ acid
• Fixed Acid – non-volatile

Answer 3

volatile

Question 4

Buffer Mechanism

• Buffers – are substances that prevent marked change in pH of solution when an acid or base is added to it; consist of weak acid (or its acid salt) and basic salt of that acid
• Buffer pairs present in body fluids – mainly _________ ______, proteins, hemoglobin, acid phosphate, and sodium and potassium salts of these weak acids

Answer 4

carbonic acid

Question 5

Buffer Mechanism-1
Action of buffers to prevent marked changes in pH

Nonvolatile acids, such as hydrochloric acid, lactic acid, and ketone bodies, buffered mainly by _______ __________

Answer 5

sodium bicarbonate

Question 6

Buffer Mechanism-2
Action of buffers to prevent marked changes in pH

Volatile acids, chiefly carbonic acid, buffered mainly by _______ salts of hemoglobin and oxyhemoglobin

Answer 6

potassium

Question 7

Buffer Mechanism-3
Action of buffers to prevent marked changes in pH

The _____ shift makes it possible for carbonic acid to be buffered in the red blood cell and then carried as bicarbonate in the plasma

Answer 7

chloride

Question 8

Buffer Mechanism-4
Action of buffers to prevent marked changes in pH

Bases are buffered mainly by ______ ________(when homeostasis at pH 7.4 exists)

Answer 8

carbonic acid

Question 9

Buffer Mechanism-5
Action of buffers to prevent marked changes in pH

The Henderson-Hasselbalch equation is a mathematical formula that explains the relationship between __________ ion concentration of body fluids and the ratio of base bicarbonate to ______ ______

Answer 9

hydrogen

carbonic acid

Question 10

Mechanisms of Hydrogen Ion Regulation

A. [H+] is precisely regulated at (pH range 7.2 - 7.4)

1. Body fluid chemical buffers
 (rapid but \_\_\_\_\_\_\_\_\_\_) 
1- bicarbonate 
2- ammonia
3- proteins
4 - phosphate

B. Lungs (____, eliminates CO2)

C. Kidneys (_______, powerful); eliminates non-volatile acids

• secretes H+
• reabsorbs HCO3-
• generates new HCO3-

Answer 10

temporary

rapid

slow

Question 11

Buffer Systems in the Body x 4

___________ : most important ECF buffer
____________ : important renal tubular buffer
_________ : important renal tubular buffer #2
___________ : important intracellular buffers

Answer 11

Bicarbonate

Phosphate

Ammonia

Proteins

Question 12

(____-______% of buffering is in the cells)

Answer 12

60-70

Question 13

Importance of Buffer Systems

Normal H+ concentration = 0.00004 mmol/L
Amount of non-volatile acid produced ~ 60-80 mmol/day 80 mmol/42 L = 1.9 mmol/L
= 47,500 times > normal H+ concentration

Answer 13

Know

Question 14

Bicarbonate Buffer System

Effectiveness of buffer system depends on:

1. concentration of ___________
2. pK of system and pH of body fluids

Answer 14

reactants

Question 15

Respiratory Regulation of Acid-Base Balance

Feedback Gain = 1.0 to 3.0 (corrects 50 to ___%)

Answer 15

75

Question 16

Bicarbonate Buffer System

Is the most important buffer in ________
fluid even though the concentration of the components are low and pK of the system is 6.1, which is not very close to normal extracellular fluid pH (7.4).

Reason: the components of the system (CO2 and HCO3-) are closely regulated by the _____ and the _________

Answer 16

extracellular

lungs

kidneys

Question 17

Urinary Mechanism

1. Reabsorption of HCO3-
2. Excretion of fixed H+ produced from ________ and phospholipid catabolism

Answer 17

protein

Question 18

Bicarbonate Reabsorption-1

Effect of filtered load of HCO3-
– ________ HCO3- exceeds the reabsorptive capacity

Answer 18

Excess

Question 19

Bicarbonate Reabsorption-2

Effect of ECF volume
– ECF volume expansion ________ HCO3- reabsorption
– ECF volume contraction _________ HCO3- reabsorption
– Angiotensin II mechanism

Answer 19

inhibits

stimulates

Question 20

Bicarbonate Reabsorption-3

Effect of CO2
– Increase in pCO2 = _________ in HCO3- reabsorption
– Decrease in pCO2 = _________ in HCO3- reabsorption

Answer 20

increase

decrease

Question 21

Excretion of H+ as NH4+–1

Effect of acidosis on NH3 synthesis
– Acidosis increases _________ metabolism

Answer 21

glutamine

Question 22

Excretion of H+ as NH4+—2

Effect of plasma K+ concentration on NH3
synthesis
– Hyperkalemia _______ NH3 synthesis, causing type 4 renal tubular acidosis
– Hypokalemia _________ NH3 synthesis

Answer 22

inhibits

stimulates

Question 23

Acid-Base DISORDERS

• _________ acid-base disorders – primary disorders involving HCO3-
• _______ acid-base disorders – primary disorders involving CO2
• Therefore, there are four simple acid-base disorders.
• There can also be mixed acid-base disorders.

Answer 23

Metabolic

Respiratory

Question 24

Plasma Anion Gap-1

• A measurement useful in diagnosis of acid- base disorders
• Based on principle of ________________
• Unmeasured anions = gap
• Normal range: 8-16 mEq/L

Answer 24

electroneutrality

Question 25

Plasma Anion Gap-2 * Useful primarily in the differential diagnosis of ___________ diagnosis * If HCO3- is replaced by unmeasured anions, the calculated anion gap is __________ * If HCO3- is replaced by Cl-, the calculated anion gap is normal

Answer 25

metabolic increased

Question 26

Anion Gap as a Diagnostic Tool In body fluids: total ________ = total anions Anion Gap – is defined as the difference between unmeasured anions and unmeasured cations Normal anion gap = 8 - 16 mEq / L

Answer 26

Cations

Question 27

Plasma Anion Gap-3 • Metabolic acidosis with ______ anion gap ``` – Diabetic ketoacidosis – Lactic acidosis – Salicylate poisoning – Methanol poisoning – Ethylene glycol poisoning – Chronic renal failure ```

Answer 27

increased

Question 28

Plasma Anion Gap-4 • Metabolic acidosis with _______ anion gap • No organic anion is accumulated – Diarrhea – Renal tubular acidosis

Answer 28

normal

Question 29

Renal Compensation for Acidosis Increased addition of HCO3- to body by kidneys (increased H+ loss by ________) This can increase to as high as 500 mmol/day

Answer 29

kidneys

Question 30

Renal Compensation for Alkalosis HCO3- excretion can ______ markedly in alkalosis

Answer 30

increase

Question 31

Renal Compensations for Acid-Base Disorders 1. Acidosis: - _________ H+ excretion - increased HCO3- reabsorption - production of new HCO3- 2. Alkalosis: - ___________ H+ excretion - decreased HCO3- reabsorption - loss of HCO3- in urine

Answer 31

increased decreased

Question 32

Acid-Base Disturbances Respiratory ________ : - brain damage - pneumonia - emphysema - other lung disorders

Answer 32

Acidosis

Question 33

Acid-Base Disturbances Respiratory __________: - high altitude - psychic (fear, pain, etc)

Answer 33

Alkalosis

Question 34

Acid-Base Disturbances Metabolic __________: - increased base intake (e.g. NaHCO3) - vomiting gastric acid - mineralocorticoid excess - overuse of diuretics (except carbonic anhydrase inhibitors)

Answer 34

Alkalosis