Fluid and Electrolyte Balance

A set of vocabulary flashcards based on important concepts related to fluid and electrolyte balance, their functions, regulation, and clinical significance.

Sodium

Main extracellular fluid (ECF) cation that regulates fluid balance and osmolality.

Potassium

Main intracellular fluid (ICF) cation crucial for muscle and nerve function important for cardiac function

Calcium (Ca²⁺)

Key electrolyte important for bone health, muscle contraction, nerve transmission, and blood clotting.

Phosphate (PO₄³⁻)

Essential for bone mineralization, ATP production, cell signaling, and as an acid-base buffer.

Magnesium (Mg²⁺)

Plays a role in enzyme function, nerve transmission, muscle relaxation, and cardiac conduction.

Osmosis

Movement of water across a semi-permeable membrane from low to high solute concentration.

Isotonic

Solution where solute concentration is equal between extracellular fluid (ECF) and intracellular fluid (ICF).

Hypotonic

Solution with lower solute concentration in ECF compared to ICF, causing cells to swell.

Hypertonic

Solution with higher solute concentration in ECF compared to ICF, causing cells to shrink.

RAAS (Renin-Angiotensin-Aldosterone System)

A complex hormonal system that plays a crucial role in regulating blood pressure, fluid, and electrolyte balance. It is activated in response to decreased blood pressure or reduced renal perfusion. This system involves a cascade of events:

1. The kidneys release renin.

2. Renin converts angiotensinogen (a protein produced by the liver) into angiotensin I.

3. Angiotensin-Converting Enzyme (ACE), primarily found in the lungs, converts angiotensin I into angiotensin II.

4. Angiotensin II is a potent vasoconstrictor, directly narrowing blood vessels to increase blood pressure. It also stimulates the adrenal cortex to release aldosterone and the posterior pituitary to release ADH (Antidiuretic Hormone). Additionally, it promotes thirst.

5. Aldosterone acts on the kidneys to increase sodium ($\text{Na}^{+}$) and water reabsorption back into the blood, while simultaneously increasing potassium ($\text{K}^{+}$) excretion. This further contributes to increased blood volume and blood pressure.

6. ADH (also known as vasopressin) increases water reabsorption in the renal tubules, leading to more concentrated urine and conserving body water.
   All these actions combined ultimately lead to an increase in blood volume and systemic blood pressure.

ADH (Antidiuretic Hormone)

Hormone that increases water reabsorption in the kidneys, concentrating urine. Ex- Vasopressin

Hydrostatic Pressure

Pressure that pushes fluid out of capillaries into surrounding tissues.

Oncotic Pressure

Pressure that pulls fluid back into capillaries due to plasma proteins.

Hyponatremia

Low sodium levels in the blood (<135 mEq/L), can cause confusion and seizures.

Hypernatremia

High sodium levels in the blood (>145 mEq/L), leading to thirst and possible seizures.

Hypokalemia

Low potassium levels in the blood (<3.5 mEq/L), causing muscle weakness and cardiac changes.

Hyperkalemia

High potassium levels in the blood (>5.0 mEq/L), associated with risk of arrhythmias.

Hypocalcemia

Low calcium levels in the blood causing increased neuromuscular excitability. Clinical manifestations include tetany (involuntary muscle contractions), paresthesia (tingling or numbness), muscle cramps, and neurological symptoms such as seizures. Specific signs include Chvostek's sign (facial muscle twitching upon tapping the facial nerve) and Trousseau's sign (carpopedal spasm induced by inflating a blood pressure cuff).

Hypercalcemia

High calcium levels in the blood (>10.5 mg/dL), leading to stones, bones, groans, and moans.

Hypophosphatemia

Low phosphate levels in the blood (<2.5 mg/dL), associated with weakness and refeeding syndrome.

Hyperphosphatemia

High phosphate levels in the blood (>4.5 mg/dL), commonly due to renal failure.

Fluid Compartment

Body divisions where fluids are distributed, mainly intracellular fluid (ICF) and extracellular fluid (ECF).