Fluid Balance and Dehydration Quiz

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Questions and Answers

Which condition is characterized by excessive fluid in the extracellular fluid, resulting in tissue swelling while cell volume remains unchanged?

Dehydration

Edema (correct)

Hypotonic hydration

Hypervolemia

What is a common early symptom of dehydration?

Increased urine output

Swelling of tissue cells

Nausea

Cotton mouth (correct)

In hypotonic hydration, what causes the cells to swell?

Decreased extracellular fluid osmolality (correct)

Increased blood pressure

Decreased intracellular fluid volume

Increased extracellular fluid osmolality

What could lead to hypovolemic shock as a result of severe dehydration?

Profuse sweating Signup and view all the answers

Which treatment is indicated for acute hyponatremia caused by hypotonic hydration?

Hypertonic saline Signup and view all the answers

What is the major cation found in intracellular fluid (ICF)?

K+ Signup and view all the answers

Which fluid compartment has the highest concentration of soluble proteins?

Intracellular fluid Signup and view all the answers

How does water predominantly move between fluid compartments?

Along osmotic gradients Signup and view all the answers

What happens when there is a high intake of salt and the osmolality of extracellular fluid (ECF) increases?

Water shifts out of cells into ECF Signup and view all the answers

Which of the following statements is true regarding the composition of extracellular fluid (ECF)?

Plasma within ECF contains more proteins than interstitial fluid. Signup and view all the answers

What occurs at the venule end of a capillary?

Most of the fluid reenters the capillary. Signup and view all the answers

Which of the following correctly describes the movement of nutrients and waste between interstitial fluid (IF) and intracellular fluid (ICF)?

It primarily involves bidirectional flow of water. Signup and view all the answers

What is the most numerous type of solute in body fluids?

Electrolytes Signup and view all the answers

What serum chloride level is indicative of hypochloremia?

< 95 mEq / L Signup and view all the answers

Which of the following can lead to metabolic alkalosis?

Vomiting Signup and view all the answers

Which condition is associated with hypercalcemia?

Hyperparathyroidism Signup and view all the answers

What is a consequence of hypercalcemia?

Cardiac arrhythmias Signup and view all the answers

Which of the following conditions can lead to hypochloremia?

Excessive ingestion of alkaline substances Signup and view all the answers

What serum level indicates hypercalcemia?

<blockquote> 10.5 mg% and > 5.2 mEq / L </blockquote> Signup and view all the answers

What might occur as a result of prolonged immobilization?

Hypercalcemia Signup and view all the answers

Which of the following symptoms is NOT associated with hypercalcemia?

Increased energy levels Signup and view all the answers

What is the primary role of atrial natriuretic peptide (ANP) in blood pressure regulation?

Decrease blood pressure and blood volume Signup and view all the answers

How does ANP affect the levels of ADH, renin, and aldosterone?

It inhibits their production Signup and view all the answers

Which female sex hormone is known to mimic aldosterone by increasing Na+ reabsorption?

Estrogen Signup and view all the answers

What effect does progesterone have on sodium and water balance?

It causes mild diuresis Signup and view all the answers

What is the consequence of high levels of glucocorticoids on sodium balance?

They cause salt and water retention Signup and view all the answers

How do cardiovascular baroreceptors respond when blood volume and pressure rise?

Decrease sympathetic output to the kidneys Signup and view all the answers

What is the outcome of dilating afferent arterioles in the kidneys?

Increased glomerular filtration rate (GFR) Signup and view all the answers

Which hormone likely blocks aldosterone receptors, leading to its diuretic effect?

Progesterone Signup and view all the answers

What physiological process is primarily involved in the renal regulation of pH balance?

Reabsorption of filtered HCO3− Signup and view all the answers

What is coupled with the reabsorption of filtered HCO3− in the kidneys?

Secretion of H+ ions Signup and view all the answers

Which of the following indicates a role of H+ in renal regulation?

Facilitating bicarbonate reabsorption Signup and view all the answers

In the context of the renal regulation of pH, what is HCO3−?

A buffer Signup and view all the answers

What happens when there is an excess secretion of H+ ions in the kidneys?

Increased HCO3− reabsorption Signup and view all the answers

How does the renal system contribute to the maintenance of acid-base balance?

By adjusting bicarbonate and hydrogen ion levels Signup and view all the answers

Which statement best describes the relationship between HCO3− and H+ in renal regulation?

H+ secretion increases HCO3− reabsorption Signup and view all the answers

Which ion's secretion is critical in the process of renal regulation of pH?

H+ (hydrogen) Signup and view all the answers

What indicates respiratory acidosis regarding blood pH and PCO2 levels?

pH below 7.35 and PCO2 above 45 mm Hg Signup and view all the answers

How do the kidneys respond to compensate for respiratory acidosis?

They secrete more H + and reabsorb HCO3 − Signup and view all the answers

Which condition indicates that the kidneys are failing to compensate for respiratory alkalosis?

pH above 7.45 with low PCO2 and low HCO3 − Signup and view all the answers

What is the primary risk for newborns in relation to kidney function and fluid balance?

Dehydration and acidosis due to inefficient kidney function Signup and view all the answers

What change occurs in fluid balance as people age?

Total body water decreases, primarily ICF decreases Signup and view all the answers

Which factor contributes to fluid imbalance risks in infants?

Higher surface area leading to greater water loss Signup and view all the answers

Why are elderly individuals at a higher risk for dehydration?

Decreased responsiveness to thirst signals Signup and view all the answers

Renal compensation cannot occur for which type of acid-base imbalance?

Imbalances in the alkaline reserve Signup and view all the answers

Study Notes

Body Water Content

Total body water varies based on age, body mass, and body fat
Infants have ~73% or more body water (low body fat).
Body water content declines to ~45% in old age.
Adult males generally have ~60% body water (higher muscle mass).
Adult females generally have ~50% body water (higher fat content, less skeletal muscle mass).
Skeletal muscle tissue is ~75% water.
Adipose tissue is less than 20% water (lowest of all tissues).

Fluid Compartments

Total body fluid in adults averages ~40 liters.
Two major fluid compartments:
Intracellular fluid (ICF): fluid inside cells, ~25 liters (~2/3 of total body fluid).
Extracellular fluid (ECF): fluid outside cells, ~15 liters (~1/3 of total body fluid).
Two major ECF compartments:
Plasma: fluid part of blood (3 liters).
Interstitial fluid (IF): fills spaces between cells (12 liters).

Composition of Body Fluids

Water is the universal solvent for electrolytes and nonelectrolytes.
Water moves from areas of lower osmolality to higher osmolality.
Electrolytes are molecules that dissociate into ions in water (conduct an electrical current).
Examples include inorganic salts, acids, bases, and some proteins.
Electrolytes have greater osmotic power than nonelectrolytes.
Nonelectrolytes are molecules that do not dissociate into ions (e.g., glucose, lipids, creatinine, urea).
Solute concentration is expressed in milliequivalents per liter (mEq/L), a measure of electrical charges.
1 mEq of single-charged ions (like Na+) equals 1 mOsm.
1 mEq of bivalent ions (like Ca²+) equals 0.5 mOsm.

Composition of Extracellular and Intracellular Fluids

Extracellular fluid (ECF) contains higher Na⁺ concentration than intracellular fluid (ICF).
ECF major anion: Cl⁻.
ICF (low in Na⁺ and Cl⁻): contains 3x more soluble proteins than plasma.
ICF major cation: K⁺ .
ICF major anion: HPO₄²⁻
Proteins, phospholipids, cholesterol, and triglycerides make up a large portion of the mass of dissolved solutes.
90% of mass in plasma, 60% in interstitial fluid (IF), and 97% in intracellular fluid (ICF).

Fluid Movement Among Compartments

Fluids continually exchange and mix between compartments via osmotic and hydrostatic pressures.
Water moves freely between compartments along osmotic gradients.
Many solutes cannot move freely due to size or charge.
Any difference in solute concentration leads to net water movement.
Exchanges occur between plasma and IF across capillary walls.
Fluid leaks from the arteriolar end of capillaries, most is reabsorbed at the venule end.
Exchanges between IF and ICF occur across plasma membranes.
Large intake of salt leads to water shifting out of cells and into the ECF.

Exchange of Gases, Nutrients, Water and Wastes

A continuous exchange of gases, nutrient, water, and wastes occurs between the three fluid compartments.

Regulation of Water Intake and Output

Water intake equals water output (~2500 ml/day).
Water gains primarily come from ingested foods and beverages.
A small amount of water is produced via cellular metabolism.
Insensible water loss occurs across skin and airways.
Sensible water loss occurs via urine (~60%), sweat, and feces
Osmolality should remain around 280-300 mOsm.
Increased osmolality stimulates thirst and ADH release.
Decreased osmolality inhibits thirst and ADH release.

Regulation of Water Intake

Hypothalamic thirst centers control thirst, stimulated by:
Osmoreceptors (activated by elevated plasma osmolality).
Dry mouth.
Decreased blood volume/pressure.

The Thirst Mechanism

The thirst center (in the hypothalamus) is triggered by ECF osmolality, resulting in increased water intake.

Regulation of Water Output

Obligatory water losses:
Insensible water loss across skin and airways.
Sensible water loss via urine (~500 ml/day), sweat, and feces.
Volume and solute concentration of urine depend on intake, diet, and variable water loss via sweat (substantial in heat) and feces (substantial with diarrhea).
Kidneys begin to eliminate excess water within 30 minutes of ingestion (peaks at ~1 hour).
ADH release takes time to be inhibited.

Influence of Antidiuretic Hormone (ADH)

Water reabsorption in collecting ducts is proportional to ADH release.
Fall in ADH decreases body fluid volume.
Rise in ADH concentrates urine.
ADH release is stimulated by:
Rise in ECF osmolality.
Drop in blood volume/pressure.

Disorders of Water Balance

Dehydration: ECF fluid loss due to hemorrhage, severe burns, prolonged vomiting, diarrhea, or excessive sweating.
Symptoms include thirst, dry skin, reduced urine output (oliguria).
Hypotonic hydration: excess water ingestion or renal insufficiency leads to a decrease in ECF osmolality.
Symptoms include nausea, vomiting, muscular cramping, and cerebral edema.
Edema: accumulation of interstitial fluid; causes tissue swelling.
Causes include conditions that increase fluid outflow of blood or reduce fluid return to blood.

Regulation of Sodium Balance

Na⁺ is important in maintaining water balance and blood pressure.
Aldosterone plays a major role in regulating Na⁺ content.
High levels of aldosterone lead to active reabsorption of Na⁺ in the distal convoluted tubule (DCT) and collecting duct (CD).
Water follows Na⁺, leading to increased ECF volume
Low levels of aldosterone lead to excretion of Na⁺ in urine.
Water follows Na⁺, leading to decreased ECF volume
Various factors influence aldosterone release, including renin-angiotensin-aldosterone system (RAAS), changes in blood pressure, and K⁺ concentration.
ANP, secreted by atria of heart, inhibits aldosterone, renin, and ADH; this reduces Na⁺ retention and increases excretion.
Other hormones like estrogens (increase Na⁺ retention), progesterone (mild diuresis), and glucocorticoids (increase Na⁺ retention) also influence Na⁺ balance.

Regulation of Potassium Balance

K⁺ is the major intracellular cation regulating cellular activity and resting membrane potential (RMP).
High ECF K⁺ causes depolarization which lowers excitability.
Hypokalemia (low ECF K⁺) cause hyperpolarization, reducing excitability.
Most important factor affecting K⁺ secretion is its ECF concentration.
High K⁺ intake increases K⁺ secretion and vice versa.
Aldosterone directly stimulates K⁺ secretion by principal cells; so, rising K⁺ concentrations trigger aldosterone release, increasing K⁺ secretion and promoting Na⁺ reabsorption.

Regulation of Calcium and Phosphate Balance

99% of calcium is in bones as calcium phosphate salts.
ECF concentration of calcium is primarily regulated by parathyroid hormone (PTH).
PTH increases calcium levels by targeting bone (increasing resorption), kidneys (increasing calcium reabsorption, and decreasing phosphate reabsorption), and small intestine (increasing calcium absorption).

Clinical-Homeostatic Imbalances

Severe electrolyte deficiencies can lead to cravings for salty foods (Addison's disease)
Pica: abnormal cravings for non-nutritive substances (caused by mineral deficiencies).
Sodium imbalances impact thirst and ECF volume.
Potassium and calcium imbalances alter neuromuscular excitability.

Regulation of Anions

Chloride (Cl⁻) is the most abundant ECF anion; it helps maintain normal osmotic pressure of blood.
When acidosis occurs, less Cl⁻ is reabsorbed in lieu of bicarbonate.
Most other anions have transport maximums and are excreted in urine when excess occurs.

Chemical Buffer Systems

Chemical buffers act as the first line of defense against pH changes.
The three major buffer systems include bicarbonate, phosphate, and proteins buffers.
Bicarbonate buffer system is the most important ECF buffer and the only one in blood.
Strong acid is added → HCO3⁻ ties up H⁺, forming weak acid H2CO3
Weak acid added → weakly reducing the pH decreases (or alkaline reserve) is used up
Strong base is added → H2CO3 dissociates and donates H⁺.
Phosphate buffer system is most significant intracellular buffer; important in urine
Strong acid added → HPO₄²⁻ ties up H⁺, forming dihydrogen phosphate.
Strong base added → dihydrogen phosphate forms monohydrogen phosphate.
Proteins act as both weak acids and weak bases; they tie up H⁺ and help buffer both sides of the pH range.

Respiratory Regulation of H⁺ concentration

Respiratory system eliminates CO2, lowering the concentration of carbonic acid (a weak acid) and H⁺.
A rise in arterial pCO₂ stimulates more ventilation eliminating more CO₂ lowering H⁺.
A fall in arterial pCO₂ inhibits ventilation, accumulating CO₂ which increases H⁺ production.

Renal Regulation of Acid-Base Balance

Kidneys regulate the acid-base balance by adjusting plasma bicarbonate (HCO3⁻) levels.
They do so by adjusting the excretion of acids and incorporating HCO3⁻ into the blood supply, thereby replenishing the alkaline reserve.

Developmental Aspects of Fluid, Electrolyte, and Acid-Base Balance

Infants have higher ECF volume and metabolic rates relative to adults, making them more vulnerable to fluid, electrolyte, and acid-base imbalance.
Inefficient kidneys make newborns at risk for dehydration.

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Test your knowledge on fluid balance, dehydration, and related physiological concepts. This quiz covers conditions, symptoms, and treatment approaches associated with fluid imbalances in the body. Perfect for students studying human physiology or health sciences.