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

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

Intracellular fluid (ICF)

Fluid inside cells that accounts for 2/3 of total body fluid.

Extracellular fluid (ECF)

Fluid located outside of cells.

ICF Total Body Fluid Percentage

2/3

Interstitial fluid

The fluid between cells; a component of the extracellular fluid (ECF).

Blood plasma and lymph

A component of the ECF representing 8% of the total.

Transcellular fluid

A component of the ECF representing 2% of the total, including CSF and humors.

CSF

Cerebrospinal fluid, a type of transcellular fluid.

Synovial fluid

A type of transcellular fluid found in joints.

Vitreous humor

A type of transcellular fluid found in the eye.

Aqueous humor

A type of transcellular fluid found in the eye.

Osmosis driver

The relative concentrations of solutes in each fluid compartment.

Principal governs of water distribution

Electrolytes.

Fluid balance

State reached when daily water gains and losses are equal, approximately $2,500\,mL/day$.

Metabolic water

Water produced by cellular metabolism.

Sensible water loss

Water loss that is observable; includes urine (60%), sweat (8%), and feces (4%).

Urine loss percentage

60% of water loss.

Sweat loss percentage

8% of water loss.

Feces loss percentage

$4\%$ of water loss.

Insensible water loss

Water loss that is not typically noticed, occurring through the skin and lungs.

Skin water loss

A form of insensible water loss.

Lung water loss

A form of insensible water loss.

Regulation of water intake governor

Sense of thirst.

Thirst trigger: Blood Osmolarity

Dehydration increases blood osmolarity.

Thirst trigger: Blood Volume

Reduction of blood volume reduces blood pressure.

Osmoreceptors

Sensors in the hypothalamus that detect reduced blood pressure and rising osmolarity of ECF.

Osmoreceptor location

Hypothalamus.

Hypothalamus ADH function

Promotes water conservation.

Hypothalamus thirst function

Provides the sense of thirst.

Salivation in thirst

Salivation is inhibited, leading to dry mouth.

Primary water output control

Variation in urine volume.

Urine volume adjustment basis

Adjustments in sodium reabsorption; water follows the movement of sodium.

ADH (Antidiuretic Hormone)

Provides a means of controlling water output independently of sodium.

Decreased ADH effect

Leads to dilute urine and a drop in the volume of body fluids.

Increased ADH effect

Leads to concentrated urine due to reabsorption of water, causing increased volume of body fluids.

Dehydration

ECF water loss due to factors like hemorrhage, burns, vomiting, or water deprivation.

Hemorrhage

A cause of ECF water loss leading to dehydration.

Severe burns

A cause of ECF water loss leading to dehydration.

Prolonged vomiting

A cause of ECF water loss leading to dehydration.

Profuse sweating

A cause of ECF water loss leading to dehydration.

Water deprivation

A cause of ECF water loss leading to dehydration.

Diuretic abuse

A cause of ECF water loss leading to dehydration.

Endocrine disturbances

A cause of ECF water loss leading to dehydration.

“Cottony” oral mucosa

A sign and symptom of dehydration.

Dry flushed skin

A sign and symptom of dehydration.

Hypovolemic shock

A potential consequence of severe dehydration and loss of electrolytes.

Hypotonic hydration

Cellular overhydration or water intoxication.

Renal insufficiency

A condition that can lead to hypotonic hydration.

Rapid excess water ingestion

A cause of hypotonic hydration.

Hypotonic hydration mechanism

ECF osmolality decreases, resulting in net osmosis of water into tissue cells and swelling of cells.

Hypotonic hydration symptoms

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

Cerebral edema

Swelling of the brain that may occur in hypotonic hydration and lead to death.

Electrolyte balance

Condition where the amount of electrolytes absorbed by the small intestine balances the amount lost via urine.

Small intestine role

Absorbs electrolytes to maintain balance.

Urine electrolyte role

The primary route for losing electrolytes from the body.

What is the metabolic role of electrolytes?

Electrolytes are chemically reactive and participate in metabolic processes.

Charge difference (Potential)

Electrolytes determine the electrical potential across cell membranes.

Osmolarity

The concentration of dissolved solutes in a body fluid.

Water content and distribution

Electrolytes govern the body's water distribution and total water content.

What strongly affects the osmolarity of body fluids?

Electrolytes

Primary electrolyte balance focus

Sodium balance, since it controls fluid movement.

Major cation of ECF

Sodium ($Na^+$).

Major anion of ECF

Chloride ($Cl^-$).

Major cation of ICF

Potassium ($K^+$).

Major anion of ICF

Monohydrogen phosphate ($HPO_4^{2-}$).

ICF Sodium and Chloride levels

Low levels.

Body compartment osmolarity value

$300\,mOsm/L$ in both ICF and ECF.

Sodium Homeostasis requirement

Adults need about $0.5\,g$ of sodium per day.

Typical American sodium intake

$3$ to $7\,g/day$.

Sodium balance control links

Linked to neural and hormonal control mechanisms triggered by changes in blood pressure or volume.

Aldosterone

Hormone playing the primary role in adjusting sodium excretion.

Aldosterone mechanism

Stimulates reabsorption of sodium by the kidneys.

Natriuretic peptides

Hormones that inhibit sodium reabsorption.

Potassium homeostasis

Maintained by aldosterone stimulating renal secretion of potassium.

Potassium imbalance frequency

The most common types of electrolyte imbalances.

Potassium: Action potential roles

Functions in the repolarization and hyperpolarization of action potentials.

High Potassium concentration effect

Results in depolarization leading to more excitable cells and potential cardiac arrest.

Low Potassium concentration effect

Results in less excitable cells leading to muscle weakness and decreased reflexes.

Main intracellular electrolyte

Potassium.

Brain area for fluid/electrolyte balance

Hypothalamus.

Acid-base balance

State in which the pH of body fluids is maintained within normal homeostatic limits.

ICF pH

$$7.0$$

Blood pH

$7.35$ to $7.45$

Acid

Any chemical that releases $H^+$ in a solution, lowering the pH.

Base

Any chemical that accepts $H^+$, raising the pH.

Strong acid

Releases most of its $H^+$ and strongly lowers pH.

Weak acid

Does not release lots of $H^+$ so it does not affect pH significantly.

Strong base

Has a strong tendency to accept $H^+$ and raise pH.

Weak base

Has a weaker tendency to accept $H^+$.

Buffer

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

Physiological buffer

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

Urinary system buffer role

A physiological buffer system.

Respiratory system role in acid-base balance

Acts as a physiological buffer system by regulating CO₂ levels.

Chemical buffer

Substance that binds $H^+$ and removes it from solution, or donates $H^+$ to release it.

Chemical buffer response time

Restores normal pH within fractions of a second.

Buffer system composition

Mixtures composed of a weak acid and a weak base.

Bicarbonate buffer system components

A solution of carbonic acid and bicarbonate ions.

High pH: Bicarbonate response

pH is lowered because the weak acid (carbonic acid) donates an $H^+$.

Low pH: Bicarbonate response

pH is raised because the weak base (bicarbonate) binds $H^+$.

Respiratory buffer mechanism

Adjusts pH by changing the rate and depth of breathing.

Basis for respiratory buffering

The bicarbonate buffer system.