Chapter 25 – Fluid, Electrolytes & Acid-Base Balance

A comprehensive set of fill-in-the-blank flashcards covering major concepts, hormones, electrolyte distributions, fluid movements, buffering systems, and acid–base disturbances from Chapter 25.

More adipose tissue and less skeletal muscle lead to a percentage of body water.

lower

Infants have a percentage of body fluid than elderly adults.

higher

About two-thirds of total body fluid is contained in the compartment.

intracellular (ICF)

Interstitial fluid and blood plasma together make up the compartment.

extracellular fluid (ECF)

The predominant cation in the ICF is .

K⁺ (potassium)

The most abundant cation in the ECF is .

Na⁺ (sodium)

Water moves between body compartments primarily by .

osmosis

Gaining weight from increased adipose tissue causes total body water percentage to .

decrease

During dehydration, water shifts from the into the .

cells (ICF) → blood plasma (ECF)

Fluid balance exists when fluid intake fluid output and distribution remains normal.

equals

Preformed water is obtained from food and .

drink (beverages)

Metabolic water is produced by reactions in the body.

aerobic cellular respiration

Water loss that is measurable, such as urine or sweat, is called loss.

sensible

Obligatory water loss occurs regardless of hydration state, but water loss is hormonally regulated by the kidneys.

facultative

Volume depletion involves isotonic fluid loss without change in osmolarity, whereas dehydration involves a of blood osmolarity.

rise (increase)

Accumulation of fluid in a specific location, such as edema, is called fluid .

sequestration

Decreased salivary secretions, increased blood osmolarity, and reduced blood pressure activate the center in the hypothalamus.

thirst

Stretch of the stomach wall and moist oral mucosa the thirst center.

inhibit

The four hormones that regulate output are angiotensin II, ADH, aldosterone, and .

atrial natriuretic peptide (ANP)

Urine formation is the primary means of fluid output and is adjusted by the .

kidneys

Electrolytes dissociate in water to form , whereas nonelectrolytes do not.

ions

Because it exerts the greatest osmotic force in the ECF, is often called the most important electrolyte of fluid balance.

sodium (Na⁺)

A decrease in pH (acidosis) causes K⁺ to move of cells in exchange for H⁺ moving inward.

out

Low blood pressure, low Na⁺, or high K⁺ levels can each stimulate the release of .

aldosterone

Aldosterone increases Na⁺ reabsorption and K⁺ secretion in the of the nephron.

distal tubule and collecting duct

Angiotensin II is produced when renin converts angiotensinogen to angiotensin I, which is then converted by in the lungs.

angiotensin-converting enzyme (ACE)

One effect of angiotensin II is widespread systemic that raises blood pressure.

vasoconstriction

High blood osmolarity, low blood volume, or angiotensin II stimulate the posterior pituitary to release .

antidiuretic hormone (ADH)

ADH increases water reabsorption by inserting into the collecting duct membrane.

aquaporin-2 channels

Stretch of the atrial walls due to increased venous return triggers release of .

atrial natriuretic peptide (ANP)

ANP causes vasodilation, inhibits renin, ADH, and aldosterone, and increases loss of in urine.

Na⁺ and water

Fixed (non-volatile) acids are regulated mainly by the , whereas volatile acid (carbonic acid) is regulated by the lungs.

kidneys

Protein buffering relies on amine groups that bind H⁺ and groups that release H⁺.

carboxyl

In the phosphate buffer system, HPO₄²⁻ can accept a proton to become .

H₂PO₄⁻

The principal ECF buffering pair is H₂CO₃ and .

HCO₃⁻ (bicarbonate)

Hypoventilation causes CO₂ retention and leads to respiratory .

acidosis

Infants are more prone to respiratory acidosis because they have smaller lungs and residual volume.

lower

Hyperventilation lowers CO₂, decreases H⁺, and causes blood pH to .

rise (alkalosis)

Persistent vomiting results in loss of stomach acid and can cause metabolic .

alkalosis

Uncontrolled diabetes with ketoacid production typically causes metabolic .

acidosis

Respiratory compensation for metabolic acidosis involves breathing.

increased (hyperventilation)

Renal compensation for respiratory acidosis increases secretion of into the filtrate.

H⁺

The acid formed from CO₂ in the body is .

carbonic acid (H₂CO₃)

During hyperventilation, blood CO₂ , blood H⁺ , and blood pH .

decreases; decreases; increases

The three major chemical buffers are the protein buffer (in cells & plasma), the phosphate buffer (in cells & urine), and the buffer (in ECF).

bicarbonate

An acid-base disturbance that is fully corrected by compensation returns pH to normal and is called imbalance.

compensated

Airway obstruction typically produces respiratory .

acidosis

Metabolic alkalosis can be caused by excessive loss of through vomiting.

hydrochloric acid (HCl)

In renal compensation for alkalosis, the kidneys secrete less H⁺ and excrete more .

bicarbonate (HCO₃⁻)

When aldosterone binds its receptors in kidney cells, synthesis of Na⁺/K⁺ pumps and Na⁺ channels .

increases

Compared with angiotensin II, ADH has a stronger effect on reabsorption but a weaker effect on vasoconstriction.

water

ANP’s overall effect on blood volume and pressure is to them, opposite to angiotensin II, ADH, and aldosterone.

decrease

Fixed acids arise from nutrient metabolism, such as lactic acid from anaerobic glycolysis and acids from lipid breakdown.

fatty

The kidneys eliminate excess H⁺ by binding it to buffers (such as phosphate or ammonia) and synthesizing new .

bicarbonate

When blood pH rises, the respiratory center is inhibited, causing CO₂ to and pH to fall back toward normal.

accumulate (increase)

A large drop in blood pressure or sympathetic stimulation of JG cells increases release from the kidneys.

renin

Binding of aldosterone increases K⁺ into the tubular fluid.

secretion

A compensated imbalance keeps pH within normal limits, whereas an imbalance does not restore pH.

uncompensated

If plasma osmolarity rises, osmoreceptors in the hypothalamus trigger release and thirst.

ADH

Fluid intake primarily comes from ingested liquids and food moisture.

preformed

Excessive hypotonic fluid intake can cause hydration, leading to cellular swelling.

hypotonic (water intoxication)

Electrolyte concentration is expressed as milliequivalents per liter, which accounts for both concentration and of each ion.

charge (valence)