Chapter 26: Fluids and Electrolytes

Vocabulary flashcards based on key concepts from Chapter 26: Fluids and Electrolytes, focusing on definitions and processes crucial for understanding body fluid dynamics and pH regulation.

Importance of Water

Water is crucial for maintaining homeostasis, regulating body temperature, transporting nutrients, and enabling biochemical reactions.

Definition of homeostasis in the context of water's role

Maintaining stable internal conditions such as blood volume, pressure, and solute concentrations.

How water regulates body temperature

Due to its high heat capacity, water absorbs and releases heat slowly, and evaporation of sweat cools the body.

Role of water in transporting nutrients and waste

Acts as a universal solvent in blood plasma and other body fluids, facilitating the movement of substances.

Role of water in biochemical reactions

Serves as a reactant in hydrolysis reactions and as the medium for most metabolic processes.

Key hormones that primarily regulate water balance

Antidiuretic Hormone (ADH) and Aldosterone.

Fluid Compartments

Fluid compartments refer to the distribution of fluids in the body, primarily divided into intracellular fluid (ICF) and extracellular fluid (ECF).

Two major fluid compartments in the body

Intracellular Fluid (ICF) and Extracellular Fluid (ECF).

Percentage of total body water constituted by Intracellular Fluid (ICF)

Two-thirds (approximately 67%) of total body water.

Percentage of total body water constituted by Extracellular Fluid (ECF)

One-third (approximately 33%) of total body water.

Primary sub-compartments of Extracellular Fluid (ECF)

Interstitial fluid and plasma, with a minor amount as transcellular fluid.

Transcellular fluid

Fluid found in specialized cavities, such as cerebrospinal fluid, synovial fluid, pleural fluid, and pericardial fluid.

Osmosis

The process by which water travels across a semipermeable membrane toward a higher solute concentration, until equilibrium is achieved.

Characteristic of a semipermeable membrane

Allows solvent (water) to pass through but restricts or limits the movement of solutes.

Aquaporins

Specific protein channels that facilitate the rapid movement of water across cell membranes.

Definition of an isotonic solution

A solution with the same solute concentration as the cell's cytoplasm, resulting in no net water movement and stable cell volume.

Definition of a hypotonic solution

A solution with a lower solute concentration than the cell's cytoplasm, causing water to enter the cell and potentially swell or lyse.

Definition of a hypertonic solution

A solution with a higher solute concentration than the cell's cytoplasm, causing water to leave the cell and shrink (crenate).

Intracellular Fluid (ICF)

Fluid within the plasma membranes of cells, accounting for two-thirds of the total body water.

Major cations found predominantly in ICF

Potassium (K^{+}) and Magnesium (Mg^{2+}).

Major anions found predominantly in ICF

Phosphate (PO_4^{3-}) and proteins.

Extracellular Fluid (ECF)

Fluid outside cells, comprising one-third of body water, including interstitial fluid and plasma.

Interstitial Fluid

The fluid that bathes cells, surrounding them outside of blood vessels, and constitutes approximately 80% of ECF.

Major cations found predominantly in ECF

Sodium (Na^{+}) and Calcium (Ca^{2+}).

Major anions found predominantly in ECF

Chloride (Cl^{-}) and Bicarbonate (HCO_3^{-}) .

Plasma

The fluid portion of blood containing cells, proteins, electrolytes, nutrients, and waste, representing about 30% of extracellular fluid.

Primary components of plasma

Largely water, along with proteins (e.g., albumin, globulins, fibrinogen), electrolytes, nutrients, hormones, and metabolic waste products.

Main protein responsible for plasma osmotic pressure

Albumin.

Facilitated Diffusion

A process where ions move across a cell membrane with the help of specialized channels due to their charge.

Type of transporter used in facilitated diffusion for glucose

Carrier proteins, which bind to glucose and change conformation to move it across the membrane.

Difference between a channel protein and a carrier protein in facilitated diffusion

Channels form a pore for ions to flow through, while carriers bind to a specific solute and undergo a conformational change to transport it.

Sodium-Potassium Pump

An essential mechanism using ATP energy to transport sodium out of and potassium into cells, maintaining concentration gradients.

Number of sodium ions (Na^{+}) pumped out by the Sodium-Potassium Pump per ATP molecule used

Three (3) Na^{+} ions.

Number of potassium ions (K^{+}) pumped into the cell by the Sodium-Potassium Pump per ATP molecule used

Two (2) K^{+} ions.

Primary energy source for the Sodium-Potassium Pump

The hydrolysis of ATP (adenosine triphosphate).

Key function of the Sodium-Potassium Pump in nerve and muscle cells

Establishing and maintaining the resting membrane potential critical for electrical signaling.

Role of the Sodium-Potassium Pump in cell volume regulation

By actively pumping out solutes, it prevents excessive water influx and subsequent cell swelling.

Osmoreceptors

Sensory receptors in the hypothalamus that monitor blood solute concentration and regulate thirst and water retention.

Part of the brain containing osmoreceptors

The hypothalamus.

Specific change detected by hypothalamic osmoreceptors

Increased extracellular fluid (ECF) osmolarity, which signifies higher blood solute concentration or dehydration.

Two primary responses triggered by activated osmoreceptors

Stimulation of the thirst center and release of Antidiuretic Hormone (ADH) from the posterior pituitary.

Primary effect of Antidiuretic Hormone (ADH)

Increases water reabsorption from the renal tubules in the kidneys, reducing urine output.

Metabolic Water

Water produced from cellular processes, particularly during aerobic respiration, totaling about 230 mL generated per day.

Cellular process that primarily generates metabolic water

Aerobic respiration, specifically during the electron transport chain where oxygen acts as the final electron acceptor.

Approximately how much water is generated daily as metabolic water

About 230 mL per day.

Diuretics

Substances that promote water loss through urine, resulting in decreased blood volume and lower blood pressure.

How most diuretics promote water loss

By inhibiting the reabsorption of sodium (Na^{+}) and chloride (Cl^{-}) in different parts of the renal tubules, leading to water following passively by osmosis into the urine.

Common therapeutic uses for diuretics

Treating hypertension (high blood pressure) and edema (fluid retention).

Loop diuretic

A class of powerful diuretics that act on the thick ascending loop of Henle in the kidney to inhibit electrolyte reabsorption.

Water Intoxication

A condition induced by excessive water intake that dilutes solute concentrations in the extracellular fluid, potentially causing cells to swell and impair neurological function.

Medical term for low sodium concentration in the blood, often associated with water intoxication

Hyponatremia.

How hyponatremia affects cells

It decreases ECF osmolarity, causing water to shift into cells to balance osmotic pressure, leading to cellular swelling, especially in brain cells.

Neurological symptoms of water intoxication

Headache, confusion, nausea, seizures, and in severe cases, coma and death due to brain swelling.

Edema

The accumulation of excess fluid in interstitial spaces that can arise from medical conditions, medications, or injuries.

Cause of edema due to increased capillary hydrostatic pressure

Elevated pressure within blood capillaries, which forces more fluid out of the capillaries and into the interstitial space (e.g., heart failure).

Cause of edema due to decreased plasma osmotic pressure

Reduced concentration of plasma proteins, particularly albumin, which decreases the osmotic pull for fluid to return to the capillaries (e.g., liver disease, malnutrition).

How lymphatic obstruction contributes to edema

Prevents the normal drainage of interstitial fluid by the lymphatic system, leading to its accumulation in tissues.

Electrolyte

Ions that help transmit electrical impulses in neurons and muscles and stabilize protein structures.

Three major cations (positively charged electrolytes) in the body

Sodium (Na^{+}), Potassium (K^{+}), Calcium (Ca^{2+}), and Magnesium (Mg^{2+}).

Three major anions (negatively charged electrolytes) in the body

Chloride (Cl^{-}), Bicarbonate (HCO3^{-}), and Phosphate (PO4^{3-}) .

Primary roles of calcium (Ca^{2+}) as an electrolyte

Essential for bone and tooth formation, muscle contraction, neurotransmitter release, and blood clotting.

Primary roles of chloride (Cl^{-}) as an electrolyte

Helps maintain osmotic pressure, is a component of stomach acid (HCl), and is involved in the chloride shift in red blood cells.

pH Level Importance

Critical for enzyme function, metabolism, muscle and nerve function, and overall cellular health.

Normal pH range for human blood

7.35 - 7.45.

Why maintaining pH is critical for enzyme function

Enzymes have optimal pH ranges; deviations outside this range can alter their structure (denaturation) and render them inactive.

Buffer Systems

Combinations of weak acids and conjugate bases that maintain pH balance by absorbing or releasing hydrogen ions as needed.

Three primary buffer systems in the body

The bicarbonate buffer system, phosphate buffer system, and protein buffer system.

How protein buffer systems work

Amino acids have carboxyl groups (COOH) that can release H^{+} and amino groups (NH_2) that can accept H^{+} ions, acting as both weak acids and bases.

Bicarbonate

A key buffer that neutralizes hydrogen ions to maintain blood pH levels; increases when the body becomes too acidic.

Chemical reaction when excess hydrogen ions (H^{+}) are present in the bicarbonate buffer system

H^{+} + HCO3^{-} ightleftharpoons H2CO3 (carbonic acid), which then dissociates into CO2 and H_2O, removed by respiration.

Chemical reaction when there is a deficit of hydrogen ions (H^{+}) in the bicarbonate buffer system

H2CO3
ightleftharpoons H^{+} + HCO_3^{-} (carbonic acid dissociates to release H^{+}).

Respiratory System Regulation of pH

The respiratory system controls blood pH by adjusting carbon dioxide levels through changes in breathing rate.

How hyperventilation affects blood pH

Increases blood pH (becomes more alkaline) by expelling more CO2, thereby decreasing carbonic acid (H2CO_3) and hydrogen ion (H^{+}) concentrations.

How hypoventilation affects blood pH

Decreases blood pH (becomes more acidic) by retaining CO2, which leads to an increase in carbonic acid (H2CO_3) and hydrogen ion (H^{+}) concentrations.

Kidney Regulation of pH

The kidneys help maintain pH by conserving bicarbonate and excreting excess hydrogen ions.

How the kidneys regulate pH regarding bicarbonate

They reabsorb filtered bicarbonate (HCO_3^{-}) from the renal tubules and generate new bicarbonate for the blood.

How the kidneys regulate pH regarding hydrogen ions

They actively secrete excess hydrogen ions (H^{+}) into the urine.

Urinary buffers used by the kidneys to excrete H^{+}

The phosphate buffer system and the ammonia (NH3)/ammonium (NH4^{+}) system.

Respiratory Acidosis

A condition characterized by the accumulation of carbon dioxide in the blood due to slow breathing.

Primary cause of respiratory acidosis

Hypoventilation, leading to an increase in the partial pressure of carbon dioxide (pCO_2) in the blood.

How the kidneys compensate for respiratory acidosis

They increase the secretion of hydrogen ions (H^{+}) and enhance the reabsorption and generation of bicarbonate (HCO_3^{-}) to raise blood pH.

Metabolic Acidosis

A condition resulting in lowered blood pH due to insufficient bicarbonate or excess acid.

Some causes of metabolic acidosis

Diabetic ketoacidosis, lactic acidosis, severe diarrhea (loss of bicarbonate), and kidney failure.

How the respiratory system compensates for metabolic acidosis

Increases breathing rate and depth (hyperventilation) to expel more CO_2, which helps to reduce H^{+} concentration and raise pH.

Compensation for Metabolic Acidosis

An increase in respiratory rate occurs to expel CO_2 and raise blood pH back to normal.

Immediate physiological response in compensation for metabolic acidosis

An increased rate and depth of breathing, often referred to as Kussmaul respiration.