Water, Electrolytes, and Acid-Base Balance Lecture Notes

Flashcards covering the properties of water, fluid compartments, hormonal regulation of blood pressure, electrolyte functions, and acid-base balance mechanisms.

Water in Lean Tissue

Composes approximately $3/4$ of the weight of lean tissue.

Water in Fat Tissue

Composes less than $1/4$ of the weight of fat tissue.

Total Body Water (Adults)

The fluid as a percentage of body weight in adults, ranging from $55$ to $60\%$.

Total Body Water (Full term newborn)

The fluid as a percentage of body weight in a full term newborn, ranging from $70$ to $80\%$.

Water Content of the Brain

The brain consists of approximately $90\%$ water.

Water Content of Blood

Blood consists of approximately $83\%$ water.

Thermoregulation

The regulation of body temperature through sweat evaporation and heat absorption due to water's high specific heat.

Healthy Urine Volume

A volume of $1$ to $2$ liters per day.

Unhealthy Urine Volume

A volume of less than $600\,mL$, which increases the risk of kidney stones.

Recommended Water Intake (Men)

The National Academies of Sciences recommends approximately $3.7$ liters/day (15-16 cups).

Recommended Water Intake (Women)

The National Academies of Sciences recommends approximately $2.7$ liters/day (11-12 cups).

Diuretics

Substances such as coffee, tea, soda, wine, and alcohol that are not good substitutes for water because they promote fluid loss.

Intracellular Fluid (ICF)

Fluid found inside the cells, making up about $2/3$ of total body water (approximately $28\,L$ in a $70\,kg$ adult).

Extracellular Fluid (ECF)

Fluid found outside the cells, making up about $1/3$ of total body water (approximately $14\,L$ in a $70\,kg$ adult).

Interstitial Fluid

A subdivision of extracellular fluid that includes fluid between cells, lymph, GI fluids, spinal column fluid, tears, and synovial fluid.

Water Balance

The dynamic equilibrium between the amount of water the body takes in and the amount it loses each day.

Thirst

A conscious desire to drink and a homeostatic mechanism that ensures plasma osmolality stays within a narrow range.

Dehydration (1-2% loss)

Triggers thirst, fatigue, weakness, vague discomfort, and loss of appetite.

Dehydration (7-10% loss)

Triggers dizziness, spastic muscles, loss of balance, delirium, exhaustion, and collapse.

Water Intoxication

A rare condition caused by excessive water intake that exceeds the kidney's ability to excrete it, leading to the dilution of electrolytes.

Psychogenic Polydipsia

A psychiatric condition where a person compulsively drinks water, potentially leading to water intoxication.

Hyponatremia

A condition where sodium levels in the blood drop, often occurring when water enters cells via osmosis during water intoxication.

Obligatory Water Excretion

The minimum amount of water the body must excrete daily as urine, approximately $500\,mL$.

ADH (Antidiuretic Hormone/Vasopressin)

A hormone released from the posterior pituitary that causes water retention by stimulating kidneys to reabsorb water.

Aldosterone

A hormone from the adrenal cortex that stimulates sodium reabsorption in kidneys; water follows the sodium, increasing blood volume.

Renin

An enzyme released by the kidneys when blood pressure drops; it activates the RAAS pathway to raise blood pressure.

Atrial Natriuretic Peptide (ANP)

A hormone from the atria of the heart that promotes the excretion of sodium and water to decrease blood volume and pressure.

Electrolytes

Salts that dissolve in water and dissociate into charged particles called ions, helping maintain fluid distribution and $pH$ balance.

Osmotic Pressure

The movement of water toward the side in which solutes are more concentrated.

Sodium ($Na^+$)

The main cation in extracellular fluid (ECF) that controls ECF volume and nerve transmission.

Potassium ($K^+$)

The main cation in intracellular fluid (ICF) that regulates ICF volume and heart function.

Chloride ($Cl^-$)

The main anion in extracellular fluid (ECF) that maintains electrical neutrality.

Phosphate ($HPO_{4}^{2-}$)

The main anion in intracellular fluid (ICF) involved in energy transfer ($ATP$) and bone health.

pH

A measure of the concentration of $H^+$ ions in a fluid.

Acidosis

A condition where blood $pH$ is less than $7.35$, indicating too much acid.

Alkalosis

A condition where blood $pH$ is greater than $7.45$, indicating too much base.

Bicarbonate Buffer System

The most important buffer system in extracellular fluid ($ECF$), using $HCO_{3}^{-}$ and $H_{2}CO_{3}$ to neutralize acids and bases.

Respiratory Regulation of pH

The lungs manage acidity by regulating $CO_{2}$ exhalation; breathing increases to lower acidity and slows to increase it.

Renal Regulation of pH

A slow response where kidneys maintain $pH$ by excreting $H^+$ and reabsorbing bicarbonate ($HCO_{3}^{-}$).

Daily Water Needs (Children)\n\n

Children generally require about 1 to 2 liters/day, depending on age and activity level.

Signs of Dehydration\n\n

Include dry mouth, fatigue, dizziness, decreased urine output, and confusion.

Rehydration Strategies\n\n

Include drinking water, electrolyte solutions, and consuming hydrating foods like fruits.

Fluid Intake Sources\n\n

Includes beverages and foods; approximately 20% of daily fluid needs typically come from food.

Effects of Caffeine\n\n

Caffeine can have a mild diuretic effect but does not significantly contribute to dehydration.

Water's Role in Digestion\n\n

Water is essential for digestion, aiding in the breakdown and absorption of nutrients.

Electrolyte Imbalance Symptoms\n\n

Symptoms may include muscle cramps, fatigue, irregular heartbeat, and confusion.

Importance of Hydration\n\n

Maintaining proper hydration is crucial for overall health, affecting physical performance, cognitive function, and metabolic processes.

Electrolyte Sources\n\n

Key dietary sources include fruits, vegetables, dairy, and nuts, which help replenish electrolytes lost through sweat and urine.

Water Loss Mechanisms\n\n

The body loses water through urine, sweat, breath, and feces, necessitating regular fluid intake to maintain balance.

Thirst Mechanism\n\n

The hypothalamus triggers the sensation of thirst in response to increased blood osmolality or decreased blood volume.

Role of Water in Temperature Regulation\n\n

Water helps regulate body temperature through perspiration and the absorption of heat, preventing overheating.

Impact of Alcohol on Hydration\n\n

Alcohol acts as a diuretic, increasing urine production and potentially leading to dehydration.

Signs of Overhydration\n\n

Symptoms include nausea, headache, confusion, and swelling, indicating excessive water intake that dilutes electrolytes.

Dehydration Symptoms\n\n

Severe thirst, very dry mouth, extreme fatigue, and lack of urine production.

Optimal Urine Color\n\n

Light yellow color indicates proper hydration; dark yellow suggests dehydration.

Sports Drinks\n\n

Beverages designed to replenish electrolytes and fluids lost during intense physical activity.

Hydration for Athletes\n\n

Athletes may require higher fluid intake to maintain peak performance and prevent dehydration during exercise.

Daily Water Needs (Adults)\n\n

Generally recommended to drink about 2.7 liters/day for women and 3.7 liters/day for men to stay hydrated.

Drinking Habits\n\n

Cultivating regular drinking habits can help prevent dehydration and maintain optimal hydration levels.

Hydration and Mental Performance\n\n

Adequate hydration is linked to better concentration, memory, and cognitive function.

Hyperhydration

A condition resulting from excessive fluid intake that can lead to electrolyte imbalances and health issues.

Water Content in Muscle Tissue

Muscle tissue is composed of approximately 75% water, playing a crucial role in nutrient transportation and energy production.

Signs of Electrolyte Imbalance

Symptoms may include muscle twitching, weakness, headache, and nausea.

Benefits of Hydration for Skin

Adequate hydration helps maintain skin elasticity, reducing dryness and the appearance of wrinkles.

Hydration During Exercise

It is recommended to drink fluids before, during, and after exercise to prevent dehydration and optimize performance.

Hydration in Hot Weather

Increased fluid intake is essential during hot weather to compensate for higher water loss through sweat.

Hydration Methods

Hydration can be achieved through various methods, including drinking water, consuming foods with high water content, and using electrolyte drinks.

Signs of Heat Exhaustion\n\n

Symptoms include heavy sweating, weakness, dizziness, nausea, and headache due to dehydration and overheating.

Hydration and Physical Recovery\n\n

Proper hydration aids in muscle recovery and reduces delayed onset muscle soreness (DOMS) after exercise.

Electrolyte Replacement Timing\n\n

Electrolyte drinks should be consumed before, during, and after prolonged physical activities to prevent imbalances.

Hydration for Elderly\n\n

Older adults may have a diminished thirst response and may need reminders to drink adequate fluids throughout the day.

Role of Water in Nutrient Transport\n\n

Water facilitates the transportation of nutrients in the body, ensuring cells receive essential substances for function.

Differences in Hydration Needs\n\n

Hydration needs vary based on factors such as age, activity level, climate, and overall health status.

Hydration and Digestion\n\n

Sufficient water intake is essential for proper digestion, helping to dissolve nutrients and prevent constipation.