Chapter 24: Fluid, Electrolyte, and Acid-Base Balance Flashcards

Practice flashcards covering Chapter 24: Fluid, Electrolyte, and Acid-Base Balance from lecture notes.

What is the title of Chapter 24?

Fluid, Electrolyte, and Acid-Base Balance

What are the two main fluid compartments in the body?

Intracellular fluid (ICF) and Extracellular fluid (ECF)

What fraction of total body fluid is accounted for by Intracellular fluid (ICF)?

$$2/3$$

Where is Intracellular fluid (ICF) located?

Inside cells

Where is Extracellular fluid (ECF) located?

Outside of cells

What is the specific name for the 25% of ECF found between cells?

Tissue (interstitial) fluid

What percentage of ECF is comprised of blood plasma and lymph?

$$8\%$$

What percentage of ECF is comprised of transcellular fluid?

$$2\%$$

Name the four examples of transcellular fluid listed in the notes.

CSF, synovial, vitreous, and aqueous humors

How is fluid continually exchanged between compartments?

Through osmosis

What determines the osmosis from one fluid compartment to another?

The relative concentrations of solutes in each compartment

Most solute particles in the body fluids are _____________.

Electrolytes

What play the principal role in governing the body’s water distribution and total water content?

Electrolytes

What is defined as the state when daily water gains and losses are equal?

Fluid balance

What is the approximate volume of daily water gains and losses for fluid balance?

About $2,500\,mL/day$

What are the primary sources for water gain?

Ingested foods and beverages

What is the term for water produced by cellular metabolism?

Metabolic water

Which organ accounts for the largest percentage of obligatory water loss ($60\%$)?

Urine (kidneys)

What percentage of obligatory water loss occurs through sweat?

$$8\%$$

What percentage of obligatory water loss occurs through feces?

$$4\%$$

What is the term for water lost through the skin and lungs?

Insensible water loss

What sense mainly governs fluid intake?

Sense of thirst

What two conditions lead to the sensation of thirst?

Increased blood osmolarity and reduced blood pressure

What causes blood osmolarity to increase and blood volume to reduce during thirst?

Dehydration

Which brain region contains osmoreceptors to detect reduced BP and rising ECF osmolarity?

The hypothalamus

What hormone is released by the hypothalamus to promote water conservation?

ADH (Antidiuretic Hormone)

How does the hypothalamus contribute to water intake besides ADH release?

It provides the sense of thirst

How is the mouth affected by thirst regulation in the hypothalamus?

Salivation is inhibited, leading to dry mouth

What is the only significant way to control water output?

Variation in urine volume

To what adjustment are changes in urine volume primarily linked?

Sodium reabsorption

What substance does water follow the movement of in the kidneys?

Sodium

Which hormone allows for the control of water output independently of sodium?

ADH

How does decreased ADH affect urine and body fluid volume?

It leads to dilute urine and a drop in body fluid volume

How does increased ADH affect urine and body fluid volume?

It leads to concentrated urine and increased body fluid volume

What causes the urine to be concentrated when ADH increases?

Reabsorption of water

What are the common causes of dehydration involving ECF water loss?

Hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, diuretic abuse, and endocrine disturbances

What is a sign of dehydration involving the oral mucosa?

"Cottony" oral mucosa

What are two common symptoms of dehydration involving the skin and sensation?

Thirst and dry flushed skin

What temperature-related symptom may result from dehydration?

Fever

What cognitive symptom may appear due to dehydration?

Mental confusion

What type of shock can result from severe dehydration?

Hypovolemic shock

What is another term for Hypotonic hydration?

Cellular overhydration or water intoxication

Under what two conditions does hypotonic hydration typically occur?

Renal insufficiency or rapid excess water ingestion

What happens to ECF osmolality during hypotonic hydration?

ECF osmolality decreases

What is the result of decreased ECF osmolality on tissue cells?

Net osmosis of water into tissue cells and swelling of cells

List five symptoms of hypotonic hydration.

Severe metabolic disturbances, nausea, vomiting, muscular cramping, and cerebral edema

What is the most severe potential outcome of hypotonic hydration?

Death

How is electrolyte balance defined?

The amount of electrolytes absorbed by the small intestine balances the amount lost (urine)

List four physiological reasons why electrolytes are important.

They participate in metabolism, determine membrane potential, affect osmolarity, and affect water distribution

Electrolyte balance usually refers primarily to the balance of which specific electrolyte?

Sodium

Why does sodium balance dominate electrolyte balance discussions?

It controls fluid movement

Each fluid compartment has a distinctive pattern of ___________.

Electrolytes

What is the major cation of the Extracellular Fluid (ECF)?

$$Na^{+}$$

What is the major anion of the ECF?

$$Cl^{-}$$

How are the levels of $Na^{+}$ and $Cl^{-}$ characterized in the Intracellular Fluid (ICF)?

Low

What is the major cation of the Intracellular Fluid (ICF)?

$$K^{+}$$

What is the major anion of the ICF?

$HPO_4^{2-}$ (monohydrogen phosphate)

Despite different electrolyte patterns, what is the osmolarity of both the ECF and ICF?

$$300\,mOsm/L$$

How much sodium per day does an adult adult need?

About $0.5\,g$

What is the sodium content of a typical American diet?

$$3\,\text{to}\,7\,g/day$$

What mechanisms are linked to sodium ($Na^{+}$) balance?

Neural and hormonal control mechanisms

What triggers neural and hormonal controls to regulate sodium content?

Changes in blood pressure or volume

Which hormone plays the primary role in adjusting sodium excretion?

Aldosterone

What is the function of Aldosterone in the kidneys regarding sodium?

Stimulates reabsorption of sodium

What substances decrease sodium reabsorption?

Natriuretic peptides

Which hormone regulates the renal excretion of potassium?

Aldosterone

Which electrolyte is involved in the most serious types of imbalances?

Potassium

What are the two electrical functions of potassium in action potentials?

Repolarization and hyperpolarization

What is the consequence of high potassium concentrations on cell excitability?

Cells become more excitable

High potassium concentrations can lead to what fatal condition?

Cardiac arrest

What is the consequence of low potassium concentrations on cell excitability?

Cells become less excitable

What are two clinical symptoms of low potassium concentrations?

Muscle weakness and decreased reflexes

Where is the main intracellular electrolyte located?

Potassium ($K^{+}$)

Which area of the brain is critical for water and electrolyte balance?

The hypothalamus

Define Acid-base balance.

A state in which the pH of body fluids is maintained within normal homeostatic limits

What is the normal pH of the Intracellular fluid (ICF)?

$$7.0$$

What is the normal pH range of blood?

$$7.35\,\text{to}\,7.45$$

What determines the pH of a solution?

Concentration of free hydrogen ions

What is the definition of an acid?

Any chemical that releases $H^{+}$ in a solution

How does an acid affect the pH of a solution?

It lowers the pH

What is the definition of a base?

Any chemical that binds $H^{+}$

How does a base affect the pH of a solution?

It raises the pH

How is a strong acid characterized?

It releases most of its $H^{+}$ and strongly lowers pH

How is a weak acid characterized?

It does not release lots of $H^{+}$ and does not significantly affect pH

How is a strong base characterized?

It has a strong tendency to accept $H^{+}$ and raise pH

What is a buffer?

Any mechanism that resists pH changes by converting a strong acid or base to a weak one

What are the two types of buffer systems in the body?

Physiological and chemical buffers

Define a physiological buffer.

A system that stabilizes pH by controlling the body’s output of acids, bases, or $CO_2$

Name the two organ systems that act as physiological buffers.

The urinary system and the respiratory system

Define a chemical buffer.

A substance that binds $H^{+}$ and removes it from solution, or a substance that donates $H^{+}$ and releases it

How quickly do chemical buffers restore normal pH?

In fractions of a second

What are chemical buffer systems composed of?

Mixtures of weak acids and weak bases

What are the two components of the bicarbonate buffer system?

Carbonic acid ($H_2CO_3$) and bicarbonate ions ($HCO_3^{-}$)

How does the bicarbonate buffer system react to a high pH (low $H^{+}$)?

The weak acid donates a $H^{+}$ to lower pH

How does the bicarbonate buffer system react to a low pH (high $H^{+}$)?

The weak base binds $H^{+}$ to raise pH

How does the respiratory buffer system adjust pH?

By changing the rate and depth of breathing

What system serves as the basis for the strong buffering capacity of the respiratory system?

The bicarbonate buffer system

What effect does the addition of $CO_2$ to body fluids have on pH and $H^{+}$ concentration?

It raises $H^{+}$ concentration and lowers pH

What effect does the removal of $CO_2$ from body fluids have on pH and $H^{+}$ concentration?

It lowers $H^{+}$ concentration and raises pH

Which system can neutralize more acid or base than any other?

The urinary system