Body Fluid Compartments; osmolality

Question 1

Body fat content varies inversely with what?

Answer 1

Water content

*this is why females have less water content than males*

Question 2

What percent of water is interstitial fluid?

What percent of our boddy water is intracellular?

Answer 2

interstitial fluid = 15% body weight

intracellular fluid = 40% body weight

Question 3

How much fluid makes up our Total Body fluid?

Answer 3

42 Liters - makes up 60% body weight overall

Question 4

What do extra and intracellular fluids contain?

Answer 4

mainly water and electrolytes -as well as small quantities of non-electrolytes like amino acids, glucose etc.

Question 5

In the extra cellular fluid, what ion is mainly present?

Answer 5

Na+ is the main positively charged ion

Cl - is the mian negatively charged ion

There is very little K+ in the ECF

Question 6

What is the main ion present in the Intracellular fluid?

Answer 6

K+ is the main positively charged ion in the ICF

PO4- and proteins are the main negatively charged ion s

Question 7

The process of maintaining the extracellular fluid through control mechanisms in the body is called…?

Answer 7

homeostasis

Question 8

Describe one mechanism of ECF homeostastic control in the body related to glucose

Answer 8

After a meal when the glucose conc. is increased- body releases insulin to remove the glucose from the ECF - thus maintaining the body homeostasis

Question 9

Big picture, are the ECF and ICF contents similar in ionic strength? Or do they vary?

Answer 9

They are near equal - there is only a slight difference that allows for action potentials

Question 10

Does water freely move across cell membranes?

Answer 10

Yes - osmosis

Question 11

What determines whether osmosis will occur or not?

Answer 11

there must be a difference in water concentrations

Question 12

Describe what high osmotic pressure means

Answer 12

The higher the osmotic pressure of a solution, the lower the water concentration and the higher the solute concentration in the solution

Question 13

The osmotic pressure exerted by particles in a solution is determined by ….?

Answer 13

the number of the particles per unit volume of fluid … not by the mass of the particles themselves

Question 14

What is an osmole?

Answer 14

osmole refers to the number of osmotically active particles in a solution rather than molar concentration.

so a solution of 1 mole of glucose/liter has an osmolar concetnration of

1 osmole/L

Question 15

What is the difference between osmolarity and osmolality?

Answer 15

osmolarity - used when the osmotically effective concentration of a solution is expressed in osmoles/Liter solution

osmolality - used when the osmotically effective concentration of a solution is expressed in osmoles/Kg solvent

*for dilute solutions like body fluids, osmolarity equals osmolality

Question 16

Diabetes insipidus is characterised by what?

Answer 16

deficiency in Vasopressin (antidiuretic hormone) which would normally reduce urinary output and conserve water in the body

With diabetes insipidus, patients can produce up to 20L of very dilute urine daily

Question 17

Why is it dangerous to be dehydrated or underhydrated?

Answer 17

Water can leave the cells by osmosis through the membranes thus increasing the osmolarity of the intercellular fluid and disrupting cellular function

mild cases = dry skin/tongue/sunken eyeballs

moderate cases = mental confusion/irrationality

sever = delirium, convulsions, coma

Question 18

Why is water retention/overhydration possibly dangerous?

Answer 18

any free surplus H2O is promptly excreted so overhydration generally does not occur. In patients with renal failure, they cannot excrete dilute urine and they thus become hypotonic upon consuming more H2O.

This leads to decreased osmolarity (saltiness) of the ICF = disrupts cellular function

symptoms mainly effect neurological function - confusion, lethargy, headache, dizziness, vomiting, severe cases of coma or death

Question 19

What is Diabetes Mellitus type 1 and 2 characterized by?

Answer 19

results from absolue or functional deficiency of circulating insulin - characterized by hyperglycemia

*because glucose is osmotically active, hyperglycemia leads to increased osmolarity in the ECF -causing intracellular dehydration.

Question 20

What are the classic symptoms of diabetes mellitus?

Answer 20

polyuria (glucose in urine)

intracellular and extracellular dehydration

increased thirst

Question 21

What does Tonicity measure?

Answer 21

tonicity is a measure of the osmotic pressure gradient of two solutions separated by a semipermeable membrane - it is influenced only by solutes that cannot cross the plasma membrane

i.e) hypertonic, isotonic, or hypotonic

Question 22

What occurs when a RBC is placed in a hypertonic solution?

Answer 22

a hypertonic solution has an osmotically effective concentration which is greater than that of ECF - therefore the RBC loses water

Question 23

What are the three principle forms of intravenous solutions given?

Answer 23

Colloid solution = hypertonic to reduce edema

crystalloid solutions = (can be isotonic to replace salt loss, hypotonic to correct hyperosmolar state, or hypertonic to correct overhydration and expland plasma volume)

blood products

Question 24

What class intravenous fluid is most commonly used?

Answer 24

Crystalloids

Question 25

Isotonic saline is administered to patients with… ?

Answer 25

low ECF volume (dehydrated) - it will distribute throughout the ECF increasing the ECF volume without altering the ECF osmolarity

Question 26

hypertonic solutions are given to patients who…?

Answer 26

to patients whose plasma osmolarity is low and as a result, water has moved into cells (overhydration)

Question 27

Hypotonic solutions are given to whom?

Answer 27

patients whose body fluids are hyperosmotic -

Question 28

Why might a colloid be used instead of a hypertonic crystalloid solution?

Answer 28

They have a high molecular weight so they do not cross semipermeable membranes

b/c of their high osmolarity, they can exert an osmotic force across the wall of capillaries

initially they stay almsot entirely in the intravascular space for longer periods of time - reducing the ICF that has build up in edema patients