electrolytes

Question 1

define electrolyte

Answer 1

Any substance containing free ions that make the substance
electrically conductive
◦ Electrolyte solutions are normally formed when a salt is placed into a solvent
such as water, and the individual components dissociate
◦ E.g. NaCl (s) → Na+ (aq) + Cl- (aq

Question 2

define ion

Answer 2

An atom or molecule in which the total number of electrons is not equal to
the total number of protons, giving it a net positive or negative electrical charge

Question 3

define nonelectrolyte

Answer 3

A substance whose molecules in solution do not dissociate to
ions and thus do not conduct an electric current

Question 4

what are the functions of body fluids

Answer 4

Transport gases, nutrients, wastes
*Transform food into energy
*Maintain overall function of body
*Generate electrical activity needed to power body functions
In general, fluid volume and composition are closely regulated
Environmental stress/disease → impair intake, increase fluid loss, change fluid
volume, composition, pH, distribution

Question 5

Which of the following is NOT an ion?
a) Sodium (11p+, 10e-)
b) Potassium (19p+, 18e-)
c) Calcium (20p+, 18e-)
d) Carbon (6p+, 6e-)

Answer 5

D

Question 6

Which of the following CANNOT easily
dissolve in water?
a) A molecule with nonpolar covalent bonds
b) A molecule with polar covalent bonds
c) A salt formed of ionic bonds
d) A protein with some non-polar covalent bonds, but mostly polar
covalent bonds

Answer 6

A

Question 7

how is intracellulae and interstitial fluid kept constant

Answer 7

Volume of fluid in each compartment is kept
constant. To keep water balanced, electrolytes must
be balanced as well (since water follows solutes)

Question 8

where are the only 2 places for change between extracellular fluid and intracellular fluid

Answer 8

Only 2 places for exchange between
compartments:
◦cell membranes separate intracellular
from interstitial fluid.
◦capillaries are the only BV with walls thin
enough for exchange between plasma
and interstitial fluids

Question 9

describe hydrostatic pressure and osmotic pressure in the arterial end of capillaries

Answer 9

At the arterial end of capillaries, the hydrostatic
pressure is higher than the osmotic pressure. The net
movement of fluid is outwards (filtration).

Question 10

describe hydrostatic pressure and osmotic pressure in the venous end of capillaries

Answer 10

At the venous end of capillaries, the osmotic
pressure is higher than the hydrostatic pressure. The
net movement of fluid is inwards (reabsorption)

Question 11

what happens to 85% of fluid that gets out of the capillaries through filtration

Answer 11

85% of the fluid that gets out of the capillaries
through filtration is reabsorbed by capillaries. The
remaining 15% is reabsorbed by lymph vessels.

Question 12

role of lymph vessels and lymph capillaries in electrolyte balance

Answer 12

Lymph capillaries begin in all tissues of
the body. They reabsorb interstitial fluid.
Lymph vessels drain lymph
away from tissues.
Lymph vessels merge to form increasingly larger vessels, and
eventually merge with blood vessels at the junctions of the
jugular and subclavian veins; lymph gets sent into the blood.

Question 13

What force causes filtration (movement
of fluid out of capillaries)?
a) Blood colloid osmotic pressure
b) Net filtration pressure
c) Blood hydrostatic pressure
d) Interstitial fluid pressure

Answer 13

Blood hydrostatic pressure (c): This is the pressure exerted by blood against the walls of capillaries. It forces fluid out of the capillaries into the surrounding interstitial space, driving filtration

Question 14

What force acts in retaining blood volume
in the capillaries?
a) Blood colloid osmotic pressure
b) Net filtration pressure
c) Blood hydrostatic pressure
d) Interstitial fluid pressure

Answer 14

Blood hydrostatic pressure (c): This is the force exerted by blood against the capillary walls, which promotes the movement of fluid out of the capillaries (filtration), not retention.

Question 15

how does the body maintain fluid balance

Answer 15

Body fluid
◦ All the water and dissolved solutes in the body
Homeostasis of body fluids is crucial
Malfunction may seriously endanger nervous system and organ functioning
Need to regulate
◦ Total volume of fluid
◦ Distribution of fluid
◦ Concentration of solutes and pH

Question 16

mechanisms of sodium/water balance

Answer 16

The movement of body fluids between the ICF and ECF depends primarily on
the movement of extracellular water and Na+
◦ Na+ (~95% of ECF solutes) primarily regulates osmolality
◦ i.e., Where Na+ goes, water goes!!!
The regulation of Na+ and water is linked to the regulation of the “effective
circulating volume”
◦ The portion of the ECF that fills the vascular compartment
Monitored by baroreceptors located in the vascular system and kidneys
(respond to pressure-induced stretch of vessel walls)

Question 17

where is the thirst center in the brain and what happens when you’re thristy

Answer 17

Stimulation of thirst center in hypothalamus
◦ decrease in blood volume/pressure triggers
renin-angiotensin-aldosterone pathway
◦ Neurons in mouth detect dryness
◦ Osmoreceptors detect increased osmolality
◦ Baroreceptors detect lowered blood pressure

Question 18

which hormones regulate water and solute loss

Answer 18

Under normal conditions, fluid output (loss) is
adjusted by
◦ antidiuretic hormone (ADH)
◦ atrial natriuretic peptide (ANP)
◦ angiotensin/aldosterone
all of which regulate urine production

Question 19

describe water intoxication

Answer 19

Question 20

Thirst can be stimulated by
a) Increased blood pressure
b) Decreased blood osmolarity
c) Increased blood volume
d) Decreased flow of saliva

Answer 20

Decreased flow of saliva (d): A dry mouth or reduced saliva flow is a direct and noticeable stimulus for thirst. It prompts a desire to drink water to restore hydration.

Question 21

Atrial natriuretic peptide helps to regulate
the volume and osmolarity of body fluids by
a) stimulating the desire to drink fluids to quench thirst.
b) stimulating the secretion of aldosterone.
c) increasing urinary excretion of sodium and chloride ions
accompanied by water.
d) increasing the permeability of the collecting ducts to water.
e) increasing urinary reabsorption of sodium and chloride ions
accompanied by water.

Answer 21

C

Question 22

Decreased blood sodium levels may cause
cells to swell because of decreased
interstitial fluid osmolarity.
a) True
b) False

Answer 22

true

Question 23

what are the 4 general functions of electrolytes

Answer 23

control the osmosis of water between body compartments.
◦ maintain the acid-base balance required for normal cellular activities.
◦ carry electrical current, which allows production of action potentials and
controls secretion of some hormones and neurotransmitters.
◦ cofactors needed for optimal activity of some enzymes

Question 24

All the following are functions of electrolytes in
the body EXCEPT
a) they control osmosis of water between fluid compartments
b) they act as enzymes in some metabolic pathways
c) they serve as enzyme cofactors
d) they help maintain acid-base balance
e) they carry electrical current

Answer 24

B

Question 25

describe cellular distribution of electrolytes

Answer 25

H20 crosses by osmosis via
aquaporins = osmosis
* Lipid-soluble substances dissolve in
cell membrane moving along
concentration gradients = diffusion
* O2, CO2
* Many ions require active transport
mechanisms
* Na+/K+ pump

Question 26

what is the key difference between the composition of blood vs interstitial fluid

Answer 26

The key difference
between the composition
of blood vs. interstitial
fluid is the concentration
of protein anions

Question 27

Which ion is found at a much higher
concentration in the ECF than the ICF?
a) Na +
b) Mg +2
c) K +2
d) Ca +

Answer 27

a) Na⁺ (Sodium ion):
Sodium is the major cation in the extracellular fluid (ECF) and is found at much higher concentrations there compared to the intracellular fluid (ICF). This concentration gradient is maintained by the sodium-potassium pump.

Question 28

describe sodium

Answer 28

Accounts for most of osmolarity of ECF
◦ Critical role of fluid and electrolyte balance
◦ High extracellular concentration of Na+ driven by Na+/K+ ATPase pumps
Imperative for action potentials of neurons
and muscle fibers
Average daily intake exceeds normal requirements
Regulated by hormonal controls
◦ Aldosterone, ADH, ANP…

Question 29

Edema, Hypovolemia and Na+ Imbalance

Answer 29

Sodium retention causes water retention
◦ Causes of sodium retention include renal failure and hyperaldosteronism
◦ Results in increased BP, increased blood volume and edema (abnormal
accumulation of interstitial fluid)
Excessive urinary loss of sodium causes excessive loss of water
◦ Due to inadequate secretion of aldosterone or too many diuretics
◦ Leads to hypovolemia (low blood volume)

Question 30

describe potassium

Answer 30

Is the most abundant cation in intracellular fluid.
Helps establish resting membrane potential & repolarizes nerve & muscle tissue
Helps maintain amount of intracellular fluid
Regulation is mainly by aldosterone through Na+/Cl-/K+ pumps
◦ as Na+ and Cl- are being reabsorbed, K+ is being secreted
◦ so, decreases K+ levels
Abnormal plasma K+ levels affect cardiac and neuromuscular function – can lead
to death

Question 31

chloride

Answer 31

Is the major extracellular anion
Helps regulate electrical balance across red blood cells (antiporter with HCO3-)
Contributes to forming HCl in the stomach
Regulation
◦ Processes that regulate reabsorption of Na+ in kidneys indirectly regulate
reabsorption of Cl- (because of Na+/Cl- symporters)
◦ mostly indirectly regulated by aldosterone