Fluid , Electrolyte And Acid Balance

Front 1

Water is approximately what percent of body mass?

Back 1

50-60 % in a healthy adult of average weight

Front 2

In the body, ways in which fluid is gained and ways in which fluid is lost:

Back 2

Gained: via intestinal tract (mainly) and metabolic generation

Lost: via kidneys, insensible loss (lungs, skin), feces, sensible loss [perspiration {variable}]

Front 3

What is the axiom regarding gains and losses of fluid in the body?

Back 3

Gains must equal losses.

Front 4

Define the fluid compartments in the body. Which has the greater volume , ECF or ICF?

Back 4

Extracellular Fluid

-Intravascular fluid (plasma)

-Interstitial fluid

-Compartmentalized fluid

Intracellular Fluid.

ICF has greater volume than ECF.

Front 5

The cell membranes of the body cells are freely permeable or selectively permeable?

Back 5

Selectively permeable

Front 6

Do ECF and ICF have the same composition? The same osmotic concentration?

Back 6

No, they do not have the same composition; each normally contains ions and molecules in concentrations that are peculiar to ECF and ICF respectively.

Yes, the osmotic concentrations of EFC and ICF are, however, normally the same, through the passive movement of water (osmosis) --- which, at equilibrium, equalizes the osmotic concentrations on either side of the cell membrane.

Front 7

Two exceptions to occurrences of osmosis:

Back 7

Ascending limb loop of Henle (impermeable to water)

In collecting duct in absence of ADH (no water reabsorption in absence of ADHhere, in spite of osmotic gradient)

Front 8

In fluid movement, the main concern is fluid movement between _____________________, _________________ and _____________________.

Back 8

cells of soft tissue

interstitial fluid

plasma

Front 9

Continuous exchange and mixing of body fluids is regulated by these two kinds of pressure:

Back 9

Hydrostatic pressure

Osmotic pressure

Front 10

Water moves freely between compartments along ____________________ gradients.

Back 10

Osmotic

Front 11

True or False: Anything that changes the solute concentration in any compartment leads to net water flows across cell membranes.

Back 11

True

Front 12

ICF volume is determined by _____________ (ICF/ECF) solute concentration.

Back 12

ECF

Front 13

Why are solutes unequally distributed in fluid compartments?

Back 13

Because of variance in size, electrical charge or dependence on transport proteins

Front 14

Is water movement across cell membranes an active or a passive process?

Back 14

Water movement is a passive process.

Front 15

State two ways in which water moves: 1) On the basis of water molecule concentration and 2) On the basis of solute concentration.

Back 15

1) Water moves from an area of high water molecule concentration to an area of lower water molecule concentration.

2) Water molecules move from an area of lower solute concentration to an area of higher solute concentration.
(Note that the above are just two ways of stating the same thing: how water moves.)

Front 16

If there is no net movement of water across cell membrane, the ECF and the ICF are said to be ___________________.

Back 16

Isotonic

Front 17

What are electrolytes?

Back 17

Soluble, mainly inorganic, compounds that disassociate into ions that will conduct an electrical current in solution.

Front 18

Do electrolytes contribute to the osmotic concentration gradients of solutions?

Back 18

Yes

Example: Adding salt (NaCl) to ECF increases the solute load (osmotic concentration gradient) of ECF compared to ICF. Water movement will be out of ICF into ECF.

Front 19

What are the units of expression of electrolyte concentration and how is this determined (the formula)?

Back 19

Units: mEq/L

How determined:

mEq/L = Ion concentration (mgm/L) in a solution X # of electrical charges on one ion / atomic weight of the element (mgm/mmol)

Front 20

True or False: Since electrolytes are in fact solutes, they affect water balance (through water movement by osmosis).

Back 20

True

Front 21

What is the axiom regarding electrolyte gains and losses in the body.

Back 21

Gains must equal losses

Front 22

Ions are of two types relative to the state of the electrons in their outermost electron shell. Ions with positive charges are called _________________, and ions with negative charges are called ______________________.

Back 22

Cations

Anions

Front 23

The most important Cations? The most important Anions?

Back 23

Cations : Na+, K+, Ca++, Mg++

Anions: Cl -, HCO-, HPO-, SO-

Front 24

The main/most important/dominant cation of ECF:

Back 24

Na+

Front 25

The main contributor to osmotic concentration in ECF is this cation:

Back 25

Na+

Front 26

There is a three-word axiom that describes the movement of water in relation to salt. Complete the axiom _______________ follows _________________ .

Back 26

water follows salt

Front 27

The stem-natr refers to sodium (Na+). In someone who is hypernatremic the sodium level concentration in ECF (as in blood) would be __________________ (higher/lower) than normal.

Back 27

Higher

Front 28

In someone who is hyponatremic the sodium concentration in ECF (as in blood) would be ______________________________ (Higher/lower) than normal.

Back 28

lower

Front 29

When we are under hydrated (hypovolemic), plasma is typically (hypernatremic/hyponatremic), causing water to move (into/out of) cells.

Back 29

hypernatremic / out of

Front 30

When we are over hydrated (hypervolemic), plasma is typically (hypernatemic/hyponatremic), causing water to move (into/out of) cells.

Back 30

Hyponatremic / into

Front 31

Of someone who has a serum sodium concentration of 150mEq/L:

1) Would this present a hypernatremic (hypertonic) or a hyponatremic (hypotonic) condition?

2) Which way would water move between ECF and ICF in this situation?

3) how would the body correct this condition?

Back 31

1) Hypernatremic

2) out of ICF into ECF

3) Water reabsorption to "dilute" the concentrated ECF.

Works this way : Rising osmolality of the blood is detected by osmoreceptors in the hypothalamus ==> hypothalamus stimulates release of ADH from posterior pituitary gland ==> ADH causes water reabsorption in distal DCT and in collecting duct of kidney ==> decreases osmolality of blood (returns to normal as solute concentration of blood returns to normal due to reabsorption of water) ==> hypothalamic osmoreceptors detect the change ==> ADH secretion stops

Front 32

Where in the CNS is the osmolality of blood monitored?

Back 32

Hypothalamus

Front 33

How are minor changes in Na+ concentration in the ECF handled?

Back 33

Changes in Na+ concentration in ECF and related fluid shifts are controlled by osmoreceptors in the hypothalamus, and the hypothalamus controls release of ADH (antidiuretic hormone) from the posterior pituitary gland. ADH acts to increase water reabsorption at the distal DCT and the collecting duct of kidney when solute concentration (mainly Na+ concentration) of ECF is increased. When solute concentration of ECF (blood) is lower than normal, ADH is not released, thus no water reabsorption by the DCT and collecting duct; the result is increased excretion of dilute urine.

Front 34

How are major changes in Na+ concentration in the ECF handled?

Back 34

Via the same mechanisms that regulate blood volume and blood pressure in situations of significant loss of blood volume and significant drop in systemic arterial blood pressure.

Front 35

Traditionally, people with high blood pressure or congestive heart failure are advised to restrict the amount of salt in their diets. Why?

Back 35

increase NaCl intake ==> increases NaCl absorption from small intestine ==> solute (NaCl) concentration in ECF/blood ==> increase intravascular volume ==> increase venous return ==> increase EDV (end diastolic volume) ==> increase stress/strain on weakened heart to pump increase volume ==> ESV (end systolic volume) ==> increase back pressure in pulmonary veins (increase pulmonary capillary hydrostatic pressure) ==> fluid extravasation into alveoli (pulmonary edema) ==> inhibits O2 uptake ==> hypoxia==> further impairment of cadiac function

Front 36

The main Cation of ICF :

Back 36

K+

Front 37

Where in the kidneys can K+ be reabsorbed?

Back 37

PCT, loop of Henle and collecting ducts

Front 38

K+ balance is accomplished mainly by changing the amount of K+ _________________ (reabsorbed /secreted) _____________________(into/out of) the filtrate.

Back 38

secreted

into