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

Question 1

Fluid balance

Learner objective

Answer 1

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

Question 2

Electrolyte balance

Learner objective

Answer 2

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

Question 3

Composition of intracellular fluid

Learner objective

Answer 3

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.

Question 4

Composition of Extracellular fluid’s

Learner objective

Answer 4

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.

Question 5

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

Answer 5

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.

Question 6

Identify the most frequent threats to acid base balance

Learner objective

Answer 6

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.

Question 7

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

Answer 7

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.

Question 8

Describe metabolic alkalosis

Learner objective

Answer 8

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.

Question 9

Compare respiratory acidosis with metabolic acidosis.

Learner objective

Answer 9

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

Question 10

Osmotic pressure
(check book for better definition)

Answer 10

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.

Question 11

Hydrostatic pressure
(check book for better definition)

Answer 11

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.

Question 12

fluid and electrolyte balance

Answer 12

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.

Question 13

the least hydrated type of tissue?

Answer 13

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.

Question 14

two major fluid compartments

Answer 14

intracellular fluid compartment

extracellular fluid compartment

Question 15

two major fluid compartments: intracellular fluid compartment

Answer 15

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

Question 16

two major fluid compartments: Extracellular fluid compartment

Answer 16

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.

Question 17

Extracellular fluid compartment: Transcellular fluid

Answer 17

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

Question 18

universal solvent

Answer 18

water

Question 19

solute classification

Answer 19

electrolytes

non-electrolytes

Question 20

Electrolytes include

Answer 20

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.

Question 21

Non-electrolytes include

Answer 21

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
glucose
lipids
urea

Question 22

electrolytes have more osmotic power than non-electrolytes

Answer 22

because their molecules dissociate into two or more ions.

Question 23

electrolyte concentrations in the body are expressed in?

Answer 23

milliequivalent per liter (mEq/L)

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

Question 24

Most extracellular fluids contain higher amounts of

Answer 24

Chloride
bicarbonate
sodium ions.

They have a greater concentration of calcium

Question 25

Most intracellular fluids contain higher amounts of

Answer 25

magnesium
phosphate
potassium
sulphate ions

Question 26

electrolytes are the most…

Answer 26

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%.

Question 27

net inward force

Answer 27

colloid osmotic pressure

Question 28

fluid movement key points: plasma and interstitial fluid

Answer 28

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.

Question 29

fluid movement key points: plasma membrane

Answer 29

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.

Question 30

primary fluid in the human body?

Answer 30

water

Question 31

water balance

Answer 31

total water intake equals total water output, maintained by homeostatic mechanisms

thirst is the primarily responsible for the regulation of water intake. Intense thirst comes from osmotic pressure affecting extracellular fluids on the ‘thirst centre’ in the hypothalamus.

Question 32

the body loses water in:

Answer 32

urine 60%

evaporation form skin and lungs 28%

feces 4%

sweat 8%

Question 33

total required intake of water per day?

Answer 33

2,500ml

wate 60%
foods 30%
byproduct of oxidative metabolism 10%

Question 34

kidneys role in fluid balance

Answer 34

Distal convoluted tubules of the nephrons and collecting ducts are most important in the regulation of water excreted in the urine. The epithelial linings are mostly impermeable to water unless antidiuretic hormone is present. When present, ADH increases water reabsorption to reduce urine production.

Question 35

sensible perspiration

Answer 35

Secretion through the sweat glands

maximum perspiration can reach 4 litres an hour in extreme conditions.

fever can also increase water loss.

Question 36

insensible perspiration

Answer 36

Evaporation from the skin

Question 37

Insensible water loss

Answer 37

From the lungs during breathing

Question 38

Water intake is regulated by several major types of stimuli

Answer 38

The effects of osmoreceptors

Dryness of the mouth

A decrease in blood volume or blood pressure

Altogether, thirst increases because of these events. thirst is influenced by consuming sodium such as in a snack food food, because sodium influences these events.

Question 39

Water intake is regulated by several major types of stimuli: osmoreceptors

Answer 39

In the hypothalamus, osmoreceptors monitor osmolality of the extracellular fluid by identifying changes in the stretching of plasma membranes, which are caused by the gain or loss of water.

Question 40

Water intake is regulated by several major types of stimuli: dryness of the mouth

Answer 40

Dry mouth develops when the osmotic pressure of the blood increases, causing the salivary glands to produce less saliva. They do this because the osmotic gradient that pulls water from the blood into this salivary glands is reduced.

Question 41

Water intake is regulated by several major types of stimuli: Blood volume or Blood Pressure

Answer 41

A large decrease in blood volume or blood pressure, of between 5% and 10%, also triggers thirst. Changes are based on signalling from baroreceptors, directly activating the thirst centre, and from the effects of angiotensin II.

Question 42

define: acids

Answer 42

Electrolytes that dissociate in water to release hydrogen ions are called acids

Homoeostasis requires control of acid and base concentrations in body fluids.

hydrochloric acid (strongest)
carbonic acid (weakest)

Question 43

define: bases

Answer 43

Electrolytes that release ions that combine with hydrogen ions are called basis.

Homoeostasis requires control of acid and base concentrations in body fluids.

Question 44

sources of hydrogen ions

Answer 44

Most hydrogen ions in body fluids begin as byproducts of metabolic processes.

aerobic respiration of glucose

Anaerobic respiration of glucose

Incomplete oxidation of fatty acids

Oxidation of sulphur containing amino acids

Hydrolysis of phosphoproteins

Strong acids dissociate to release hydrogen ions more completely, where where as weak acids release them less completely.

Question 45

Normal pH of intracellular fluid is?

Answer 45

On average 7.0

in the arterial blood it is 7.4

in the venous blood and interstitial fluid 7.35

The lower pH in venous blood and the cells is because of the large amounts of carbon dioxide and acid metabolites.

Question 46

Acid-base buffer systems

Answer 46

Consist of chemicals that combine with excess acids or bases.

Buffer system chemicals can combine with strong acids, which release more hydrogen ions, to convert them into weak acids, which release fewer hydrogen ions.

Question 47

The three most important acid-base buffer systems in the bodies fluids are as follows:

Answer 47

1. Bicarbonate buffer system
2. Phosphate buffer system
3. Protein buffer system

they all combine with hydrogen ions in acidic (0ph) conditions

or release hydrogen ions in alkaline/base (14ph) conditions.

Question 48

The pH of arterial blood is usually between?

Answer 48

7.35 and 7.45

Abnormal values below 7.35 produced acidosis

Values above 7.45 produce alkalosis

Question 49

Survival may be impossible with blood pH is below?

Answer 49

6.8

or above 8.0

for more then a few hours

Question 50

The two major types of acidosis are?

Answer 50

Respiratory acidosis

Metabolic acidosis

Question 51

Respiratory acidosis

Answer 51

may be caused by increased carbon dioxide concentration as well as carbonic acid or respiratory acid and may result in the following conditions:

Injury to the brain stem is respiratory centre, decreasing breathing

Obstruction of air passages and interference with air movement into alveoli

Diseases decreasing gas exchange, such as pneumonia, or reducing respiratory membrane surface area, such as emphysema. Also linked to cystic fibrosis

Question 52

Hypercapnia

Answer 52

Respiratory acidosis is generally indicated by PCO2 that is above 45 MM HG, known as hypercapnia, and lowered blood pH

Question 53

chronic respiratory acidosis

Answer 53

occurs because normal respiratory functions compromised but compensatory mechanisms haven’t completely failed.

patients who may be experiencing this could have CNS damage, have taken barbiturates, or taken alcohol. These individuals often develop acidosis because of chronic hypoventilation.

Question 54

respiratory alkolosis

Answer 54

Results from excessive carbon dioxide and carbonic acid loss.

Called hypocapnia, this condition is signified by a PCO2 of less than 35MM HG, with raised blood pH.

A temporary hypocapnia can be produced by hyperventilation. Caused by anxiety, pain, fever or poisoning.

Question 55

Hyperventilation

Answer 55

Hyperventilation depletes carbon dioxide and increases body fluid pH to as high as 8.0.

Fortunately, respiratory alkalosis is usually self corrected, it is chemoceptor stimulation stops and The urge to breathe reduces. Carbon dioxide levels then return to normal.

It gradually elevates the pH of cerebrospinal fluid, affecting CNS function.

There are initial tingling sensations in the lips, hands, and feet. The individual may be lightheaded and lose consciousness if the condition continues. Because unconsciousness stops perception of causative psychological stimuli, breathing rate declines and the condition is self corrected.

Question 56

Hyperventilation: The effects of respiratory alkalosis and compensation for the condition

Answer 56

Carbonic acid is lost by hyperventilation

The amount of sodium bicarbonate stays the same, causing pH levels to rise.

The body maintains homeostasis through bicarbonate loss by renal excretion.

This then reduces PH, back to or close to normal range.

Question 57

Metabolic acidosis

Answer 57

Metabolic acidosis is the second most common type of acid base imbalance. Metabolic imbalances such as this are indicated by bicarbonate levels below or above the normal range, which is 22 to 26MEQ/L.

Metabolic acidosis maybe caused by accumulation of non-respiratory acids or loss of bases, such as in the following conditions:

Lactic acidosis, which can develop after strenuous exercise or prolonged tissue hypoxia

Diabetes melitis, which converts some fatty acid’s into ketone bodies such as aceto-acetic acid, Beta-hydroxybutyric acid, and acetone, causing ketonuria or ketoacidosis. This conversion of some fatty acids into ketone bodies also occurs during starvation.

Over consumption of alcohol, which is metabolised to acetic acid.

Vomiting over a long period of time causes the stomach to continue to generate stomach acid’s to replace those that are lost. As a result, bicarbonate concentration of the blood continues to rise.

Prolonged diarrhoea, which is more common in infants, causing excessive loss of bicarbonate ions.

Kidney disease, causes uremic acidosis.

Question 58

Metabolic alkalosis

Answer 58

Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35–7.45). This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations.

May occur due to repeated vomiting, or too many antacids.

In metabolic alkalosis there is an increase in blood pH, called alkalaemia.

Symptoms include decreased breathing rate and depth and increased blood carbon dioxide.

The compensatory factors for metabolic alkalosis include reduced breathing rate, with a loss of bicarbonate ions in the urine.

Question 59

Compensations for imbalance

Answer 59

If the lung or kidney buffer systems become insufficient, the acid base balance is disrupted. As a result, the undisturbed system tries to compensate.

The respiratory system is responsible for compensation of metabolic acid base imbalances and works relatively quickly.

The urinary system, although slower, is responsible for compensation of respiratory related acid-base imbalances.

The ways the systems compensate are reflected in changes in the PC02 and concentrations of bicarbonate ions. A patient can have a serious medical condition and still show a normal pH because of how the systems compensate.

Question 60

Compensations for imbalance: Respiratory compensation

Answer 60

When the respiratory system compensates for a metabolic acidbase imbalance, respiratory rate and depth change.

They are usually elevated in metabolic acidosis. This is because high hydrogen ion levels stimulate the respiratory centres. Blood pH is below 7.35, and bicarbonate ions levels are below 22MEQ/L. The PCO2 falls below 35MMHG As carbon dioxide is removed and XS acid leaves the blood.

In respiratory acidosis, respiratory rate is often depressed, which is the immediate cause of the acidosis. This is not true for conditions of gas exchange impairment, such as pneumonia or emphysema.

For metabolic alkalosis, respiratory compensation involves slow and shallow breathing. This allows carbon dioxide to accumulate in the blood. Evidence of this compensation includes a pH above 7.45 at first, and sometimes longer; bicarbonate levels over 26MEQ/L; And a PCO2 above 45MM HG

Question 61

Compensations for imbalance: Urinary compensation

Answer 61

The kidneys speed up the compensatory actions when an acid base imbalance is of respiratory cause.

Acidosis is shown when a person is hyperventilating. Although the kidneys are compensating, the levels of PCO2, as well as bicarbonate ions, are high. The raised PCO2 causes the acidosis. The increasing bicarbonate ion level shows the kidneys are retaining bicarbonate to compensate for the acidosis.

Oppositely, an individual who has respiratory alkalosis compensated for by the kidneys has a high blood pH and a low PCO2.

As the kidneys eliminate more bicarbonate by not reclaiming it or by secreting it, it’s levels begin to fall. However, the kidneys cannot compensate for either alkalosis or acidosis if the condition is linked to a renal problem.

Question 62

Effects of ageing on water, electrolyte, and acid base balance

Answer 62

Total body water decreases gradually as we age, predominantly from the intracellular compartment.

These decreases reduce the dilution of waste products, toxins, and administrated medications.

The glomerular filtration rate declines, and the body cannot regulate PH via the urinary system as efficiently. More water begins to be lost because of an increased inability to concentrate the urine.

As the skin becomes thinner, the rate of insensible perspiration increases. Older adults should increase their daily water intake to combat this condition. They are less able to conserve body water than younger people and are also less responsive to thirst queues. When homoeostasis is interrupted, the body takes longer to return to normal.

Body mineral content is lower as muscles and bones decrease in mass. Body fat increases, however. Exercise and increased ingestion of dietary minerals can help in this regard. Because respiratory compensation decreases with age, the risk of respiratory acidosis increases, compounded by arthritic conditions and other conditions such as emphysema.

As the other systems in the body decline in function, they affect fluid, electrolyte, and acid base balance as well. Conditions that make the elderly more prone to acid base in balances include congestive heart failure with oedema and diabetes melitis. Nearly all disorders of the body systems, with increased ageing, partially affect the balances of fluids, electrolytes, acids, and bases.

Question 63

Effects of respiratory and metabolic acidosis and alkalosis: respiratory acidosis

Answer 63

Respiratory congestion, slow and shallow respiration is

PCO2 is increased

More hydrogen excreted by the kidneys and more bicarbonate reabsorbed

Hi PCO2 and bicarbonate levels

Compensated pH 7.35 to 7.4; decompensated pH less than 7.33

Question 64

Effects of respiratory and metabolic acidosis and alkalosis: metabolic acidosis

Answer 64

Diabetic ketoacidosis, diarrhoea, renal failure

Decreased bicarbonate, rapid and deep respirations, tissue hyperoxia

More hydrogen excreted by the kidneys; if the kidneys are not involved, there is increased bicarbonate absorption

Low PCO2 and bicarbonate levels

Compensated pH7.35 to 7.4, decompensated pH below 7.33

Question 65

Effects of respiratory and metabolic acidosis and alkalosis: respiratory alkalosis

Answer 65

Hyperventilation.

Decreased levels of PCO2.

Less hydrogen excreted by the kidneys and less bicarbonate reabsorbed.

Partial pressure of oxygen low, bicarbonate levels low.

Compensated pH 7.4-7.45; decompensated pH above 7.47

Question 66

Effects of respiratory and metabolic acidosis and alkalosis: metabolic alkalosis

Answer 66

Excessive antacid use, vomiting.

Increased bicarbonate, slow and shallow respirations.

Less hydrogen excreted by the kidneys; if the kidneys are not involved, there is decreased bicarbonate absorption.

Hi PCO2 and bicarbonate levels.

Compensated pH 7.4 to 7.45; decompensated PH above 7.47