Water, Electrolyte, pH regulation A&P2 Lec

Which fluid compartment contains approximately two-thirds of the body's total water?

Intracellular fluid (ICF)

By what process does water move between fluid compartments in response to solute concentration changes?

Osmosis

Toward which direction does water move when solute concentration increases in a specific compartment?

Toward the higher solute concentration

What are the two main components of the extracellular fluid (ECF)?

Interstitial fluid and plasma

Identify the three primary sources of body water.

Ingested liquids, food, and metabolic water

List the four primary routes of water loss from the body.

Urine, sweat, exhaled air, and feces

What is obligatory water loss?

Minimum water loss required to eliminate wastes; about 500 mL/day

How does Antidiuretic Hormone (ADH) affect urine output?

It decreases urine output by increasing water reabsorption

Which hormonal system increases both Na+ and water retention to regulate output?

RAAS (Renin-Angiotensin-Aldosterone System)

How do natriuretic peptides affect Na+ and water levels in the body?

They increase Na+ and water excretion

What clinical term describes the improper distribution of fluid into the tissues?

Edema

What is the medical term for the increased urination common to all types of diabetes?

Polyuria

What is the primary cause of diabetes insipidus?

Lack of ADH or lack of kidney response to ADH

Why does diabetes insipidus result in large volumes of dilute urine?

Water is not reabsorbed in the kidneys

What is the underlying physiological cause of diabetes mellitus?

High blood glucose

How does glucose in the urine lead to polyuria in diabetes mellitus?

It causes osmotic diuresis (water follows the glucose)

What is the functional difference between Type I and Type II diabetes mellitus?

Type I: no insulin production (autoimmune)

Type II: insulin resistance.

Which condition is characterized by high blood glucose and diabetes-like symptoms caused specifically by excess cortisol?

Adrenal diabetes

What is gestational diabetes?

Caused by pregnancy hormones; leads to insulin resistance and high blood glucose

In historical urinalysis, which form of diabetes would result in urine with a sweet taste? Which form of diabetes would result in urine with no taste?

Diabetes mellitus, which indicated glucose present

Diabetes insipidus, which indicates no glucose present

Why does alcohol consumption increase urine production?

It inhibits the release of ADH

How does caffeine act as a diuretic?

It inhibits Na+ reabsorption, causing water to remain in the urine

Roles of Sodium (Na+)

• Major ECF ion

• Fluid balance

• Nerve impulses

Roles of Potassium (K+)

• Major ICF ion

• Resting membrane potential

• Muscle & heart function

Roles of Calcium (Ca2+)

• Bone structure

• Muscle contraction

• Neurotransmitter release

• Blood clotting

Identify three physiological roles of Na+

Regulating fluid balance, blood pressure, and nerve impulses

List four physiological roles of calcium Ca2+

• Bone structure

• Muscle contraction

• Neurotransmitter release

• Blood clotting

Which hormone specifically increases K+ secretion while increasing Na+ reabsorption?

Aldosterone

What is the primary effect of Parathyroid Hormone (PTH) on blood chemistry?

It increases blood Ca2+ levels

Which hormone acts to decrease blood Ca2+ levels?

Calcitonin

What is hypernatremia? Causes and effects?

• High Na⁺; caused by excess saline.

• Causes water retention, hypertension, edema.

What is hyponatremia? Causes and effects?

• Low Na⁺; caused by fluid loss replaced with water.

• Causes diluted plasma and possible neurological problems.

A rapid rise in potassium (hyperkalemia) can lead to which life-threatening event?

Cardiac arrest due to overexcitable cells

Why does a slow rise in potassium lead to less excitable cells?

It causes Na+ channel inactivation

What is hyperkalemia? Causes and effects?

• High K⁺.

• Fast rise: overexcitable cells → cardiac arrest.

• Slow rise: less excitable cells due to Na⁺ channel inactivation.

What is hypokalemia? Causes and effects?

• Low K+

• Causes hyperpolarization → muscle weakness, arrhythmias

What is hypercalcemia? Causes and effects?

• High Ca²⁺.

• Causes decreased excitability → muscle weakness, arrhythmias.

What is hypocalcemia? Causes and effects?

• Low Ca2+

• Causes increased excitability → tetany, laryngospasm

Which abnormalities can cause muscle weakness?

Hypercalcemia and hypokalemia

Which abnormalities can cause cardiac arrest?

Hyperkalemia

Which abnormalities can cause overly excited neurons and tetany?

Hypocalcemia

What is the normal range for blood pH?

7.35-7.45

Define acidosis in terms of blood pH

Define alkalosis in terms of blood pH

A blood pH lower than 7.35

A blood pH higher than 7.45

What is the function of a chemical buffer?

A substance that resists changes in pH by binding or releasing H+

Provide the chemical equation for the bicarbonate buffer system.

CO₂ + H₂O ⇄ H₂CO₃ ⇄ H⁺ + HCO₃⁻

When does bicarbonate reaction shift toward products or reactants?

• More CO₂ → shifts right → more H⁺ (acidosis).

• Less CO₂ → shifts left → less H⁺ (alkalosis).

How do protein buffers react when the body is in a state of alkalosis?

They release H+ in alkalosis and bind H+ in acidosis

What is the chemical formula for the phosphate buffer system?

H₂PO₄⁻ ⇄ HPO₄²⁻ + H⁺

What causes metabolic acidosis?

• Lactic acid

• Ketoacids

• Renal failure

• Diarrhea

• Aspirin

• Protein metabolism acids

What causes metabolic alkalosis?

• Vomiting

• Antacids

• Digestion of alkaline foods

What causes respiratory acidosis?

Hypoventilation which leads to increased CO2

What causes respiratory alkalosis?

Hyperventilation which leads to decreased CO2

How does the respiratory system compensate for metabolic acidosis?

By increasing the rate of breathing to remove CO2

What respiratory adjustment is made to compensate for metabolic alkalosis?

Decreasing the rate of breathing to retain CO2

How do the kidneys contribute to acid-base balance?

Adjust H+ secretion and HCO₃^- reabsorption

What is 'renal compensation' for pH imbalances?

The adjustment of H+ secretion by the kidneys, which is slow but effective

Why is urine pH range wider than blood pH?

Kidneys vary urine pH to maintain stable blood pH

What happens to urine pH in acidosis?

What happens to urine pH in alkalosis?

Becomes more acidic (as low as 4.5)

Becomes more basic (up to 8.2)

How does the hemoglobin-oxygen (HB-O₂) curve shift during acidosis vs alkalosis?

Acidosis: shifts right (releases O₂).
Alkalosis: shifts left (holds O₂).

Why are enzymes sensitive to pH imbalances?

Their activity decreases when they are outside of their optimal pH range

What is the characteristic effect of severe acidosis on the brain?

Decreased activity, which can lead to a coma

How does alkalosis typically affect skeletal muscle function?

It increases excitability, potentially causing tetany