The document provides an overview of fluid compartments, electrolytes, and acid-base balance in the human body. The body contains two main fluid compartments - intracellular fluid within cells and extracellular fluid outside of cells. Electrolytes such as sodium, potassium, chloride, and bicarbonate are important for fluid balance, nerve impulses, and pH regulation. The body maintains acid-base balance through buffer systems, exhalation of carbon dioxide, and kidney excretion of acids and bases. Imbalances can occur if the pH level rises above or falls below the normal range of 7.35-7.45.

1. Overview of
Fluids,Fluids,
ElectrolytesElectrolytes
BalanceBalance
Mr. Johny Kutty Joseph, M.Sc (N), RN, RM
Assistant Professor
Shri Mata Vaishno Devi Coll

2. Fluid CompartmentsFluid Compartments
 The human body consists of 55-60% of water.
Body fluids are mainly present in two compartments
such as Intracellular space/cystosol and
Extracellular space.
The ECF consist of 80% interstitial fluid(between
cells) and 20%plasma in blood.
The interstitial fluids also include CSF, lymph,
synovial fluid etc.
The barriers that separate ICF, interstitial fluid and
blood are plasma membrane and wall of the blood
vessels.
The body maintains the fluid balance by means of
filtration reabsorption, diffusion and osmosis.

3. Solute
the substance that dissolved
Solvent
substance in which solute is dissolved
Osmolality
concentration of solute per kg of water
Osmolarity
concentration of solute per L of solution
Solution- substance that dissolve in other
substances

4. Composition of the Body FluidsComposition of the Body Fluids
The fluids circulating throughout the body in
ECF & ICF spaces contain:
1. Electrolytes
2. Minerals
3. Cells

5. Definition:Definition:
Diffusion is the natural tendency of a substance to
move from an area of higher concentration to
one of lower concentration.
OsmosisOsmosis fluid shift to the membrane from the
region of low concentration to the region of high
concentration.
Active TransportActive Transport this is movement of molecules
against a concentration as they move from an
area of lower concentration to an area of higher
concentration and requires an energy.
FiltrationFiltration movement of water & solutes occurs
from an area of high hydrostatic pressure to an
area of low.

6. OsmosisOsmosis
Figure 2.
FluidFluid
High SolutionHigh Solution
Concentration,Concentration,
Low FluidLow Fluid
ConcentrationConcentration
Low SoluteLow Solute
Concentration,Concentration,
High FluidHigh Fluid
ConcentrationConcentration

7. DiffusionDiffusion
High Solute ConcentrationHigh Solute Concentration Low Solute ConcentrationLow Solute Concentration
FluidFluid
SolutesSolutes
Figure 3.

8. Active transportActive transport
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++ KK ++
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++
KK ++ATPATP
ATPATP
ATPATP
ATPATP NaNa ++
NaNa ++
NaNa ++
NaNa ++ NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
NaNa ++
Figure 4.
INTRACELLULAR FLUIDINTRACELLULAR FLUID
EXTRACELLULAR FLUIDEXTRACELLULAR FLUID

9. BLOODBLOOD
VESSELVESSEL
NORMALNORMAL
CELLCELL
ISOTONICISOTONIC

10. BLOODBLOOD
VESSELVESSEL
SHRUNKENSHRUNKEN
CELLCELL
HYPERTONICHYPERTONIC

11. HYPOTONICHYPOTONIC
BLOODBLOOD
VESSELVESSEL SWOLLENSWOLLEN
CELLCELL

12. Water regulation
The main source of water for body are ingestion of
water and moist foods throgh GI.
The other source is metabolic water that is
produced in the body during cellular respiration.
Body fluids moreover remain constant.
Daily water gain is about 2500ml and loss is also
the same.
The intake of water is regulated by the thirst centre
in hypothalamus.
Hypothalamus is controlled by kidneys by RAA
pathway. (dehydration secrete renin.)

13. Water regulation
Another factor that control the fluid loss are Na and
Cl. These are the major ions present ECF which
regulate the process of Osmosis and thus the fluid
balance.
Two hormones also help in control fluid loss such
as aldosterone and ANP.
The hormone from posterior pituitary
ADH/vasopressin also regulate the urine output and
thus the fluid volume.

14. Electrolytes
Chemically, electrolytes are substances that become
ions in solution & acquire the capacity to conduct
electricity.
They control the process of Osmosis.
Ions help to maintain acid-base balance required for
normal cellular functioning.
 ions also carry electrical current which allow the
production of action potentials.
Some ions act as cofactors for increase enzyme
activity. For example, Mg2 is used in glycolysis.
An anion is an ion with more electrons than protons,
giving it a net negative charge.
A cation is an ion with fewer electrons than protons,

15. Sodium (Na)Sodium (Na)
The most abundant ions in the ECF: 90%
136 to 148 mEq/L is the normal level.
Major positive ion in fluid outside the cells.
Regulates the total amount of water in the
body & the transmission of into & out of
cells. (osmolarity)
 The Na level is controlled by aldosterone,
ADH and ANP.
Hyponatremia: decreased level of Na.
Hypernatremia: increased level of Na.

16. Potassium (K+)Potassium (K+)
It is abundant in ICF.
Plays major role in establishing resting
membrane potential.
Also helps in regulation of pH.
3.5 to 5.0 mEq/L is the normal range.
Regulation of the heartbeat & function of the
muscles.
Controlled by Aldosterone.
Hypokalemia: decreased K in
Hyperkalemia: increased K (cause death due to
ventricular fibrillation.)

17. Chloride (Cl-)Chloride (Cl-)
98 to 108 mmol/L
Major anion (negatively charged ion) found
outside the cells & in the blood.
Helping the body maintain a normal balance
of fluids.
Used to maintain balance between anions
and cations.
Na and Cl is dependent each other.

18. Bicarbonate (HCO3)Bicarbonate (HCO3)
22 to 26 mEq/L (anions)
The level changes as the level of CO2
changes in blood.
CO2+blood = carbonic Acid
Carbonic Acid – H+ ions = Bicarbonate.
Major role is to maintain the normal level
of pH in the blood & other fluids in the
body.
Measured to monitor the acidity of the
blood & body fluids.

19. Calcium = CaCalcium = Ca
Large amount of Ca is stored in bone.
Abundant mineral of the body.
Ca is also found in ECF but attached to
proteins.
The normal level is Ca in blood is 4.5 –
5.5 mEq/ltr.
Regulated by Parathormone (increase)
and calcitonin (decrease).
Hypercalcemia: increase Ca
Hypocalcemia: decreased Ca

20. Phosphate H2PO4Phosphate H2PO4
Found along with calcium as salts.
Negatively charged.
Normal level 1.7 – 2.6 mEq/ltr.
Regulated by Parathormone (increase)
and calcitonin (decrease).
Excretion is through kidneys.

21. Magnesium MgMagnesium Mg
Present in bone matrix.
Cofactor for metabolism of carbohydrates
and proteins.
Essential role in neuromuscular, synaptic,
myocardial activity.
Normal level 1.3 – 2.1 mEq/ltr

22. Acid Base BalanceAcid Base Balance
It is required to maintain the homeostatic
balance so as to keep the pH between
7.35 and 7.45.
The balance is made by three
mechanisms such as
1.Buffer System
2.Exhalation of CO2
3.Kidney excretion of H+

23. Buffer System
Buffering is the process of binding H+ ions
temporarily to decrease the acidity. But it does not
remove the H+ ions from the body. The major
buffer systems are
1.Protein Buffer System: Hb in RBC and albumin in
plasma. They release H+ ions when pH rises.
2.Carbonic Acid- Bicarbonate Buffer System:
balancing of H2HCO3(carbonic acid) and HCO3
(bicarbonate) in blood.
3.Phosphate Buffer System: it is the balance
between di-hydrogen phosphate (weak acid) and
mono-hydrogen phosphate(strong base).

24.  Exhalation of CO2: The breathing plays an
important role in maintaining pH. Exhalation
of CO2. It is volatile acid.
 Kidney excretion of H+: secretion of non-
volatile acid through urine. The proximal
convoluted tubules and collecting duct
secret H+ ions into urine and reabsorb Na.

25. Acid Base ImbalanceAcid Base Imbalance
Acidosis: when pH is below 7.35
Alkalosis: when pH is above 7.35.
Types:
1. Respiratory Acidosis: abnormally high PCO2 in blood
above 45mmhg. Respiratory disorders may be the
reason. (H2CO3)
2. Respiratory Alkalosis: abnormally low PCO2 in blood
below 35 mmhg. Respiratory disorders may be the
reason.
3. Metabolic Acidosis: the systemic HCO3 level drops below
22mEq/ltr. Due to renal dysfunction / diarrhoea.
4. Metabolic Alkalosis: the systemic HCO3 level is above
26mEq/ltr. Due to vomiting of gastric juices/ intake of
alkaline drugs.