AndrewAcid-Base Balance

A comprehensive set of vocabulary flashcards covering the chemical, respiratory, and urinary mechanisms of acid-base balance, pH scale principles, and metabolic and respiratory acid-base disturbances from Chapter 22.

Acid-Base Balance

The precise regulation and maintenance of a relatively constant concentration of hydrogen ions ($H^+$) in body fluids to ensure the proper functioning of vital body proteins, such as enzymes and hemoglobin.

pH

An abbreviation for "power of $H^+$" (from potenz power) that numerically indicates the relative hydrogen ion ($H^+$) concentration of a fluid compared with its hydroxide ion ($OH^-$) concentration.

Neutral Solution

A fluid with a pH of $7.0$, representing an equal concentration of hydrogen ions and hydroxide ions ($[H^+] = [OH^-]$), exemplified by pure distilled water.

Alkaline Solution

Also called a basic solution; a solution with a pH greater than $7.0$, indicating a lower concentration of hydrogen ions than hydroxide ions ($[H^+] < [OH^-]$).

Acidic Solution

A fluid with a pH less than $7.0$, indicating a higher concentration of hydrogen ions than hydroxide ions ($[H^+] > [OH^-]$).

Normal Blood pH Range

The narrow physiological range of blood plasma, between $7.35$ and $7.45$, with systemic arterial blood averaging about $7.4$ (upper limit $7.45$) and venous blood averaging about $7.37$ (not usually below $7.35$).

pH Unit

A logarithmic unit based on exponents of $10$, such that a shift of $1$ whole pH unit represents a tenfold ($10\times$) difference in actual hydrogen ion ($H^+$) concentration.

Homeostasis

The principle of constancy or balance of the internal fluid environment of the body, a term coined in $1932$ by American physiologist Walter Bradford Cannon in his book The Wisdom of the Body.

Carbonic Anhydrase (CA)

An enzyme found inside red blood cells that converts carbon dioxide and water into carbonic acid according to the reaction: $\text{CO}_2 + \text{H}_2\text{O} \xrightarrow{\text{carbonic anhydrase}} \text{H}_2\text{CO}_3$.

Chemical pH Control Mechanisms

Immediate-acting regulatory systems based on buffer salts in the blood, red blood cells, and body fluids that rapidly convert strong acids or bases into weaker ones.

Physiological pH Control Mechanisms

Regulatory systems that adjust pH by eliminating or retaining substances from the body; includes the respiratory mechanism (acting in $1\text{ to }2\text{ minutes}$) and the renal/urinary mechanism (initiating within $24\text{ hours}$).

Chemical Buffer

A chemical substance that prevents a sharp change in the pH of a fluid when an acid or a base is added to it.

Buffer Pair

A pair of related chemical compounds present in body fluids—primarily sodium bicarbonate ($\text{NaHCO}_3$) and carbonic acid ($\text{H}_2\text{CO}_3$)—that collaborate to minimize drastic fluctuations in pH.

Fixed Acids

Acids produced by catabolism, such as lactic acid, that do not break down to form a volatile gas and are buffered primarily by sodium bicarbonate ($\text{NaHCO}_3$) in the blood.

Bicarbonate-Carbonic Acid Buffer Ratio

The normal clinical ratio of sodium bicarbonate ($\text{NaHCO}_3$) to carbonic acid ($\text{H}_2\text{CO}_3$) required in arterial blood at pH $7.45$, which is precisely $20:1$.

Respiratory Mechanism of pH Control

The physiological pH regulation system wherein the brainstem adjusts breathing rate and depth to eliminate or retain $\text{CO}_2$, thereby decreasing or increasing the amount of $\text{H}_2\text{CO}_3$ and $H^+$ in the blood.

Urinary Mechanism of pH Control

The body's most effective and final regulatory defense for acid-base balance, wherein renal tubules excrete excess $H^+$ and ammonia/ammonium ions into the urine (often acidifying urine to pH $4.8$) while conserving and reabsorbing $\text{HCO}_3^-$.

Bicarbonate Loading

The ingestion of large quantities of sodium bicarbonate ($\text{NaHCO}_3$) by athletes in an attempt to buffer lactic acid buildup and stave off fatigue during strenuous anaerobic exercise, which can cause diarrhea and disrupt electrolyte balance.

Acidosis (Clinical)

A clinical condition defined by an arterial blood pH dropping below $7.35$, which rarely falls as low as $7.0$ before causing death.

Alkalosis (Clinical)

A clinical condition defined by an arterial blood pH rising above $7.45$, caused by an accumulation of bases or loss of acids.

Metabolic Acidosis

An acid-base disturbance characterized by a primary bicarbonate ($\text{HCO}_3^-$) deficit ($< 22\,\text{mEq/L}$), caused by renal disease, uncontrolled diabetes, prolonged diarrhea, or ingestion of toxins such as methanol or ethylene glycol.

Metabolic Alkalosis

An acid-base disturbance characterized by a primary bicarbonate ($\text{HCO}_3^-$) excess ($> 26\,\text{mEq/L}$), commonly caused by loss of gastric hydrochloric acid from repetitive vomiting or gastric suction, diuretic therapy, or Cushing syndrome.

Respiratory Acidosis

An acid-base disturbance characterized by carbonic acid ($\text{H}_2\text{CO}_3$) excess and an elevated arterial $P_{\text{CO}_2}$ ($> 45\,\text{mm\,Hg}$), primarily caused by hypoventilation, respiratory center depression, emphysema, pneumonia, or cardiac arrest.

Respiratory Alkalosis

An acid-base disturbance characterized by a carbonic acid ($\text{H}_2\text{CO}_3$) deficit and an abnormally low arterial $P_{\text{CO}_2}$ ($< 35\,\text{mm\,Hg}$), primarily caused by hyperventilation due to anxiety, ventilator overventilation, or hepatic coma.

Compensation

The physiological process by which pH-balancing mechanisms (chemical buffers, lungs, or kidneys) adjust to counterbalance an abnormal primary pH shift and return arterial blood pH toward the healthy range.

Diabetic Ketoacidosis (DKA)

A condition in which fat is excessively metabolized instead of carbohydrates, leading to dangerous accumulation of acidic ketone bodies in the blood, ketonuria, fruity breath, and compensatory rapid breathing to eliminate $\text{CO}_2$.

Emesis

The forceful expulsion of gastric and intestinal contents through the mouth, regulated by a vomiting center in the brainstem, which can cause severe metabolic alkalosis through massive loss of chloride ions.

Arterial Blood Gas (ABG) Analysis

A laboratory analysis of blood drawn from a systemic artery used to evaluate respiratory status and acid-base homeostasis by assessing $P_{\text{O}_2}$, $\%S_{\text{O}_2}$, pH, $[\text{HCO}_3^-]$, and $P_{\text{CO}_2}$.