Exercise 12: Acid-Base Physiology

Vocabulary flashcards covering acid-base physiology, buffering systems, homeostatic pH ranges, and respiratory/metabolic compensation mechanisms.

pH

A measure of hydrogen ion concentration ($[H^+]$) in a solution, mathematically calculated as $pH = \log\left(\frac{1}{[H^+]}\right)$, ranging on a scale from 0 to 14.

Acid

A substance that increases the concentration of hydrogen ions ($[H^+]$) in a solution, resulting in a pH value below 7 ($[H^+] > [OH^-]$).

Base

A substance that reduces the concentration of hydrogen ions ($[H^+]$) in a solution, resulting in a pH value above 7 ($[H^+] < [OH^-]$).

Strong Acid

An acid, such as $HCl$, that dissociates almost completely into its constituent ions ($H^+$ and $Cl^-$) in solution, significantly lowering the pH.

Weak Acid

An acid, such as carbonic acid ($H_2CO_3$), that dissociates only weakly and incompletely into hydrogen ions and conjugate base ions in solution.

Strong Base

A base, such as $NaOH$, that dissociates almost completely into ions in solution, raising the pH by eliminating $H^+$ through the formation of $H_2O$.

Weak Base

A base, such as sodium bicarbonate ($NaHCO_3$) or bicarbonate ion ($HCO_3^-$), that does not dissociate readily and acts as a weak hydrogen ion acceptor.

Buffer

A chemical system consisting of a weak acid and a weak base that resists changes in the pH of a solution by converting strong acids and strong bases into weak acids and weak bases.

Dissociation

The reversible or irreversible separation of a chemical compound into its constituent ions in a solution.

Carbonic Acid ($H_2CO_3$)

A weak metabolic acid formed when carbon dioxide ($CO_2$), a waste product of cellular respiration, reacts with water ($H_2O$) in cells, blood, and interstitial fluid.

Bicarbonate Buffer System

The primary circulating chemical buffer system responsible for regulating blood plasma pH, described by the reversible reaction $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$.

Phosphate Buffer System

A biological buffer system that functions primarily in urine and intracellular fluid, operating through the buffering reaction $HPO_4^{2-} + H^+ \rightarrow H_2PO_4^-$.

Law of Mass Action

A chemical principle stating that reversible chemical reactions will be driven from the side of higher concentration toward the side of lower concentration.

Carbonic Anhydrase

An enzyme located predominantly in erythrocytes that catalyzes the reversible conversion between dissolved $CO_2$ and $H_2O$ into carbonic acid ($H_2CO_3$).

Normal Arterial Blood pH Range

The tightly maintained homeostatic blood pH range in a healthy individual, spanning between 7.35 and 7.45 with an average of 7.40.

Acidosis

A clinical and physiological state in which arterial blood pH drops below 7.35.

Alkalosis

A clinical and physiological state in which arterial blood pH rises above 7.45.

Respiratory Acidosis

A drop in blood pH below 7.35 caused by hypoventilation and excessive accumulation of dissolved carbon dioxide (hypercapnia), which shifts the carbonic acid equilibrium to produce more $H^+$ ions.

Hypercapnia

An abnormal elevation of dissolved carbon dioxide ($CO_2$) in the plasma, which increases the arterial partial pressure of $CO_2$.

Metabolic Acidosis

A drop in blood pH caused by the accumulation of non-respiratory acids (such as lactic acid, fatty acids, or ketone bodies) or excessive loss of bicarbonate bases.

Respiratory Alkalosis

A rise in arterial blood pH above 7.45 caused by hyperventilation and a deficit of carbon dioxide in the plasma (hypocapnia), driving the carbonic acid reaction to the left and lowering $[H^+]$.

Hypocapnia

An abnormally low concentration of carbon dioxide ($CO_2$) in the blood plasma, lowering the arterial partial pressure of $CO_2$.

Metabolic Alkalosis

A rise in arterial blood pH above 7.45 caused by excessive loss of hydrogen ions ($H^+$) or gain in bases, such as from severe vomiting or excessive sodium bicarbonate ingestion.

Hypochloremic Alkalosis

A form of metabolic alkalosis caused by an extreme lack or loss of chloride ions (such as through prolonged vomiting), leading the kidneys to compensate by conserving bicarbonate.

Hypokalemic Alkalosis

A form of metabolic alkalosis triggered by the kidneys responding to an extreme deficiency or loss of potassium ions, often induced by diuretic drugs.

Bromothymol Blue

A pH indicator used for weak acids and bases that turns yellow in an acidic environment, green at neutral pH, and blue in a basic environment.

Thymol Blue

A pH indicator that transitions from red to yellow across the pH range of 1.2 to 2.8 and transitions from yellow to blue across the pH range of 8.0 to 9.6.

Scientific Method

A standardized, systematic approach of empirical inquiry consisting of steps to observe phenomena, formulate hypotheses, test them experimentally, and analyze results.