Chapter 21 - Fluid, Electrolyte, And Acid-Base Balance Flashcards Preview

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Flashcards in Chapter 21 - Fluid, Electrolyte, And Acid-Base Balance Deck (66)
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Fluid balance
(Learner objective)

Referring mainly to water balance, it means that total water intake equals total water output, maintained by homoeostatic mechanisms.


Electrolyte balance
(Learner objective)

When the quantities of electrolytes that the body gains equal those that it loses; also maintained by Homeostasis


Composition of intracellular fluid
(Learner objective)

Intracellular fluid is made up of water and electrolytes enclosed by cell membranes.

It contains more magnesium, phosphate, potassium, and sulphate ions and then extracellular fluid.


Composition of Extracellular fluid’s
(Learner objective)

Extracellular fluid is made up of all fluid outside of cells, which includes the plasma, lymph, interstitial fluid, and transcellular fluid.

It contains high amounts of chloride, bicarbonate, and sodium ions, as well as more calcium than is found in intracellular fluid.


Describe the movement of fluid within the extracellular and intracellular fluids.
(Learner objective)

Hydrostatic pressure and osmotic pressure regulate the movement of water and electrolytes from one fluid compartment to another.

A change in osmotic pressure usually causes net fluid movement.

When sodium ions decrease in the extracellular fluid, water moves from the extracellular compartment into the intracellular compartment via osmosis. The opposite is true when sodium ion concentration in interstitial fluid increases.


Identify the most frequent threats to acid base balance
(Learner objective)

The most common threats to acid base balance include acidosis, when the pH of arterial blood is below 7.35, and alkalosis, when pH is above 7.45.

Two major types of acidosis are respiratory acidosis and metabolic acidosis.

Likewise, the two major types of alkalosis are respiratory alkalosis and metabolic alkalosis.


Explain how the body responds when the pH of body fluids varies outside normal limits.
(Learner objective)

When normal pH levels of arterial blood are not maintained, the body responds by producing acidosis or alkalosis.

Survival may be impossible if pH is below 6.8 or above 8.0 for more than a few hours.


Describe metabolic alkalosis
(Learner objective)

Metabolic alkalosis results from excessive loss of hydrogen ions or gain of bases or bicarbonate ions.

This results in an increase in blood pH or alkalaemia. It may follow gastric drainage or lavage, use of certain diuretics, or prolonged vomiting. It also may develop from taking too many antacids.


Compare respiratory acidosis with metabolic acidosis.
(Learner objective)

The differences between respiratory and metabolic acidosis are as follows:

A. Respiratory acidosis: may be caused by increased carbon dioxide concentration as well as carbonic acid; may result in injury to the brain stems respiratory centre, obstruction of a passages, pneumonia, emphysema, or other respiratory conditions.

B. Metabolic acidosis: may be caused by accumulation of nonrespiratory acid’s or loss of bases; May result in kidney disease, diabetes melitis, long-term vomiting, prolonged diarrhoea, or lactic acidosis


Osmotic pressure
(check book for better definition)

Water moves according to osmotic gradients, meaning water always moves form an area of lesser osmolality to an area of greater osmolality.

the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis, often used to express the concentration of the solution.


Hydrostatic pressure
(check book for better definition)

the pressure exerted by a liquid as a result of its potential energy, ignoring its kinetic energy; frequently used to distinguish a true pressure from an osmotic pressure or to emphasize the variation in pressure in a column of fluid due to the effect of gravity.


fluid and electrolyte balance

The amount of water and electrolytes gained from food and beverages, on a daily basis, is equal to the amount the body loses to the environment.

The body replaces lost water and electrolytes and excretes and excess.

electrolytes are dissolved in the water of body fluids. When electrolyte concentrations are altered, water concentrations are also altered by adding or removing solutes. The reverse is also true.


the least hydrated type of tissue?

adipose tissue.

all other types of tissue including bone, have higher water concentrations.

people with greater muscle mass have more body water because skeletal muscle is made up of about 75% water.


two major fluid compartments

intracellular fluid compartment

extracellular fluid compartment


two major fluid compartments: intracellular fluid compartment

includes all water and electrolytes enclosed by cell membranes. In an adult, intracellular fluid represents about 63%, by volume, of total body water.


two major fluid compartments: Extracellular fluid compartment

includes all fluid outside cells.

makes up 37%, by volume, of total body water.

this includes:
Plasma in the blood vessels.
Lymph in the lymphatic vessels.
Interstitial fluid in the tissue spaces.

This compartment is referred to as the body's internal environment.


Extracellular fluid compartment: Transcellular fluid

some extracellular fluid is separated from other types of fluid and is known as transcellular fluid and includes:

Aqueous and vitreous humors: in the eyes

Cerebrospinal fluid: in the central nervous system

Secretions: from the exocrine glands

Serous fluid: in body cavities

Synovial fluid: in the joints


universal solvent



solute classification




Electrolytes include

inorganic salts

some proteins

acids - organic or inorganic

bases - organic or inorganic

Electrolytes have more abilty to cause fluid shifts that non-electrolytes because their molecules dissociate into two or more ions. creating higher osmotic pressure.


Non-electrolytes include

have mostly covalent bonds, meaning they cant dissociate in a solution.

No electrically charged particles are created when they dissolve in water.

most non-electrolytes are organic molecules such as: creatine


electrolytes have more osmotic power than non-electrolytes

because their molecules dissociate into two or more ions.


electrolyte concentrations in the body are expressed in?

milliequivalent per liter (mEq/L)

this measure the number of electrical charges in 1 litre of solution.


Most extracellular fluids contain higher amounts of

sodium ions.

They have a greater concentration of calcium


Most intracellular fluids contain higher amounts of

sulphate ions


electrolytes are the most...

abundant solutes in the fluids of the body and control most chemical and physical reactions.

However they do not make up most dissolved solutes in the fluids. In the extracellular fluid, proteins and certain non-electrolytes such as cholesterol, phospholipids, and triglycerides are large molecules that are present. In the plasma, these make up approximately 90% of the mass of dissolved solids and 60% in the interstitial fluid. In the intracellular fluid they make up 97%.


net inward force

colloid osmotic pressure


fluid movement key points: plasma and interstitial fluid

Exchanges between plasma and interstitial fluid occur across capillary walls, and exchanges between the interstitial fluid and intracellular fluid occur across plasma membranes. For exchanges between plasma and interstitial fluid, the bloods hydrostatic pressure forces plasma that almost totally lacks proteins into the interstitial space.
The highly filtered fluid then is almost totally reabsorbed into the bloodstream because of the colloid osmotic pressure of the plasma proteins.
Normally, lymphatic vessels pick up small amounts of net leakage remaining behind in the interstitial space, returning it to the blood.


fluid movement key points: plasma membrane

Exchanges across the plasma membranes are based on permeability. Generally, there is substantial two-way osmotic flow of water. Restriction of ion changes is based on ions moving selectively through channels or by active transport.
Nutrients, respiratory gases, and wastes usually move in one direction.
An example is how metabolic wastes move out of cells, whereas glucose and oxygen move into them. Except during the first minute after a change in one type of body fluid, osmolalities of all body fluids are equal.


primary fluid in the human body?