Cellular Environment: Fluids, Electrolytes, Acids, and Bases

This flashcard set covers the distribution of body fluids, electrolyte balances (sodium, potassium, calcium, magnesium, phosphate), and acid-base imbalances (respiratory and metabolic acidosis/alkalosis) based on the lecture transcript.

Intracellular fluid (ICF)

Fluid located inside the cell.

Extracellular fluid (ECF)

Fluid located outside the cell, including interstitial, intravascular, and cerebrospinal fluid (CSF).

Total body water in Newborns

$75\%$ to $90\%$ of body weight.

Total body water in Adults

$60\%$ of body weight.

Aquaporins

A family of water channel proteins that provide permeability to water.

Osmosis

The process by which water moves between the ICF and ECF compartments.

Net filtration

The movement across the capillary wall, equal to the forces favoring filtration minus the forces opposing filtration as described by the Starling law.

Forces favoring filtration

Capillary hydrostatic pressure (blood pressure) and interstitial oncotic pressure (water pulling).

Forces opposing filtration

Plasma oncotic pressure (water pulling) and interstitial hydrostatic pressure.

Edema

The accumulation of fluid in the interstitial spaces.

Aldosterone

A hormone that increases reabsorption of sodium by the distal tubule of the kidney.

Natriuretic peptides

Hormones including Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP) that decrease tubular resorption and promote urinary excretion of sodium.

Antidiuretic hormone (ADH)

Also called arginine vasopressin; it is released in response to increased plasma osmolality or decreased circulating blood volume to increase water reabsorption.

Hypernatremia

A serum sodium level greater than $147\,mEq/L$ related to sodium gain or water loss, leading to intracellular dehydration.

Hyponatremia

A serum sodium level less than $135\,mEq/L$ causing plasma hypoosmolality and cellular swelling.

Hypokalemia

A potassium level less than $3.5\,mEq/L$ which can cause membrane hyperpolarization, skeletal muscle weakness, and a U wave on an ECG.

Hyperkalemia

A potassium level greater than $5.5\,mEq/L$; manifestations include restlessness, intestinal cramping, and peaked T waves.

Hypocalcemia

Calcium levels less than $8.5\,mg/dl$; clinical signs include Chvostek and Trousseau signs and increased neuromuscular excitability.

Hypercalcemia

Calcium levels greater than $12\,mg/dl$; causes include hyperparathyroidism, bone metastasis, and acidosis.

Magnesium plasma concentration

Normal range of $1.8$ to $2.4\,mg/dl$. It is an intracellular cation and a co-factor in protein synthesis and nucleic acid stability.

pH

The negative logarithm of the $H^+$ concentration; normal body pH is $7.35$ to $7.45$.

Volatile Acids

Acids such as Carbonic acid ($H_2CO_3$) that can be eliminated as carbon dioxide ($CO_2$) gas via the lungs.

Nonvolatile Acids

Metabolic acids such as sulfuric and phosphoric acids that are eliminated by the renal tubules.

Buffer

A chemical that can bind excessive $H^+$ or $OH^-$ without a significant change in pH.

Carbonic acid–bicarbonate ratio

At a pH of $7.4$, the ratio of bicarbonate to carbonic acid is $20:1$.

Metabolic acidosis

A condition characterized by a depression of $HCO_3^-$ (less than $24\,mEq/L$) or an increase in noncarbonic acids, often resulting in Kussmaul respirations.

Anion gap

Represents unmeasured negative ions used to distinguish types of metabolic acidosis; the normal range is $10$ to $12\,mEq/L$.

Metabolic alkalosis

An elevation of $HCO_3^-$ (above $26\,mEq/L$) usually resulting from excessive loss of metabolic acids or chloride ($Cl^-$).

Respiratory acidosis

An elevation of $pCO_2$ (hypercapnia) resulting from alveolar hypoventilation and depression of the respiratory center.

Respiratory alkalosis

A depression of $pCO_2$ (hypocapnia) resulting from alveolar hyperventilation.