Anatomy & Physiology: Fluid, Electrolyte, and Acid-Base Balance

Vocabulary practice cards covering fluid compartments, electrolyte regulation, and acid-base balance mechanisms from Chapter 26.

Intracellular fluid (ICF)

The fluid contained within the cells of the body.

Extracellular fluid

Comprises blood plasma and the interstitial fluid ($IF$).

Interstitial fluid (IF)

The fluid located in the spaces between cells.

Capillary Hydrostatic Pressure (CHP)

The pressure that drives net filtration near the arterial end of the capillary when it is greater than $BCOP$.

Blood Colloidal Osmotic Pressure (BCOP)

The pressure that drives net reabsorption near the venous end of the capillary when it is greater than $CHP$.

Metabolic Water Production

The process described by the equation: $Glucose + O_{2} \rightarrow CO_{2} + H_{2}O + ATP$.

Osmoreceptors

Sensory receptors that detect decreased water levels in the blood to initiate the thirst response.

Antidiuretic Hormone (ADH)

Produced in the hypothalamus and released by the posterior pituitary, this hormone causes the kidneys to retain water.

Aquaporins

Water channel proteins inserted into the plasma membrane of collecting tubule cells in response to $ADH$ to increase water flow out of tubule and into the bloodstream.

Intracellular Electrolytes

The fluid group containing higher concentrations of potassium ($K^{+}$) and magnesium.

Extracellular Electrolytes

The fluid group containing higher concentrations of sodium ($Na^{+}$) and calcium.

Aldosterone

A hormone released in response to increased blood $K^{+}$ or decreased blood $Na^{+}$ that facilitates the reabsorption of $Na^{+}$ and the excretion of $K^{+}$.

Atrial Natriuretic Peptide (ANP)

A hormone secreted by the right atrium in response to atrial stretching that suppresses sodium reabsorption, leading to water loss.

Edema

An allergic reaction of accumulation of excess fluid in tissues, often caused by high BP, low albumin, leaky vessels, or a blocked lymphatic system (cancer)

pH Scale

A scale ranging from $0$ to $14$ measuring hydrogen ion concentration; $7$ is neutral, less than $7$ is acidic, and greater than $7$ is basic.

Normal Blood pH

The specific homeostatic range for blood pH, which is $7.35$ - $7.45$.

Acid

A proton donor that releases $H^{+}$ when dissolved in water, thereby lowering the pH of a solution.

Base

A proton acceptor that binds to $H^{+}$, thereby increasing the pH of a solution.

Buffer

A chemical system, such as the bicarbonate-carbonic acid system, that prevents extreme changes in blood pH.

Metabolic Acidosis

An acid-base disorder caused by conditions like diabetic ketoacidosis, diarrhea, renal failure, shock, or sepsis.

Respiratory Acidosis

An acid-base disorder caused by hypoventilation, $COPD$, airway obstruction, or drug overdose.

Metabolic Alkalosis

An acid-base disorder caused by the loss of gastric secretions, overuse of antacids, or $K^{+}$ wasting diuretics.

Respiratory Alkalosis

An acid-base disorder caused by hyperventilation, hypoxia, anxiety, high altitude, or fever.

Fluid compartments in the body

Intracellular fluid (ICF), ECF (composed of blood plasma and interstitial fluid (IF))

location of most water in the body

Intracellular fluid; second largest is the interstitial fluid

Compartments of each body fluid

Intracellular fluid, interstitial fluid, Plasma, and a small amount of other fluid

Capillary Exchange

The process by which substances move between blood in the capillaries and the interstitial fluid, involving filtration and diffusion depending on pressure gradients.

Thirst response

beings when osmoreceptors detect decreased water levels in blood

Thirst Response Regulation

triggered by insufficient water in the body resulting in decreased blood volume and increased blood osmolarity. This leads to decrease in blood pressure and activation of osmoreceptors in the hypothalamus, causing sensations of dry mouth and increases angiotensin II causing stimulation of the thirst center in hypothalamus. The increased thirst prompts water consumption, which helps to lower blood osmolarity and restore balance.

Electrolytes

Essential for neve conduction, membrane permeability, and osmolarity of body fluids

NaHCO3 + HCl → H2CO3 + NaCl

When sodium bicarbonate comes into contact with a strong acid, such as HCl,

and carbonic acid, which is a weak acid, and NaCl are formed

H2CO3 + NaOH → HCO3(-) + H2O

When carbonic acid comes into contact with a strong base, such as NaOH,

Forming bicarbonate and water

Bicarbonate-carbonic acid buffer

A weak acid or weak base functions by capturing free ions in a solution, thereby preventing significant changes in pH and maintaining homeostasis in the bloodstream.

Respiratory regulation of blood pH

When CO2 levels in the blood rise, it combines with water to form carbonic acid, lowering blood pH. To correct this, increasing breathing rate or depth helps exhale more CO2, reducing carbonic acid and raising pH back to normal.

Conversely in the opposite directioin, hyperventilation reduces CO2, leading to too much alkalinity. This can be fixed by rebreathing exhaled air from a bag to bring pH back down.

Respiratory Response to Acidosis

When blood CO2 levels increase, carbonic acid levels rise, causing a drop in blood pH (acidosis). This stimulates the brain and arterial receptors, and the body responds by increasing the respiration rate and decreasing blood CO2. This lowers blood carbonic acid (H2CO3) levels and raises blood pH restoring acid/base homeostasis

Respiratory Response to Alkalosis

When blood CO2 levels decrease, carbonic acid levels drop, causing an increase in blood pH (alkalosis). This stimulates the brain and arterial receptors, the body responds by decreasing the respiration rate, slowing down breathing, allowing Blood CO2 to increase, which raises carbonic acid levels(H2CO3) and lowers pH, restoring pH back to normal and acid/base homeostasis

Conservation of Bicarbonate in the Kidney

The kidneys conserve bicarbonate through a series of processes that allow it to be returned to the blood,

as tubular cells are not permeable to bicarbonate; this means bicarbonate is conserved rather than reabsorbed

Kidneys (regulation)

organ that plays a crucial role in maintaining blood pH by regulating bicarbonate(HCO3-) levels

Bicarbonate ions (HCO3-)

found in the filtrate; essential for the bicarbonate buffer system.

Causes of Metabolic Acidosis types

diabetic ketoacidosis, diarrhea, renal failure, shock, aspirin overdose, and sepsis

Causes of Metabolic Alkalosis

loss of gastric secretions, overuse of antacids and K+ wasting diuretics

Causes of Respiratory Acidosis

hypoventilation, COPD, Airway obstruction, drug overdose, chest trauma, pulmonary edema, and neuromuscular disease

Causes of Respiratory Alkalosis

hyperventilation, hypoxia, anxiety, high altitude, and fever