Unit 4: Renal Physiology Pt 2 Flashcards
What two things must inputs and outputs be adjusted to maintain?
- maintain ECF
- maintain osmolality
What is a typical daily fluid intake? How much of that is from ingestion of food and fluid? What about from carbohydrate oxidation?
2300 ml/day (2.3L/day)
food/fluid--> 2100 ml carbohydrate oxidation (metabolic water)--> 200 ml
What are the ways we lose body water?
- insensible water loss –> breathing and through skin
- Sweating
- feces
- via kidneys (major contributor)
What percentage of the body is fluid weight? What of that is intracellular and extracellular?
60%
- 40% intracellular fluid
- 20% extracellular fluid
“60-40-20 rule”
What ions is intracellular fluid low in? high in?
low in–> Na+, Ca++, Cl-
high in–> K+ and Phosphate
What does the extracellular fluid consist of? What ions is it high in? low in?
all fluid outside cells–> plasma and interstitial fluid
low in–> K+, phosphates, and proteins
high in–> Na+, Cl- and bicarbonate
What is the net diffusion of water across a selectively permeable membrane from a region of high water concentration to one that has a lower water concentration?
Osmosis
What is Osmotic Pressure?
the equilibrium pressure b/w:
- hydrostatic pressure (due to increase in water in a compartment–pushing water into solute free compartment)
AND
- the osmotic forces generated by the addition of a solute
What is the Osmotic Pressure proportional to?
the number of active or dissociable solute/particles in the solution (ones that cannot pass membrane)
What is the total number of particles in a solution called?
Osmoles
1 Osmole = 1 mole of solute particle
Ex: 1 mole of glucose/liter = 1osm/L
What is the difference b/w Osmolality and Osmolarity?
Osmolality = Osmoles per kilogram of water
Osmolarity = Osmoles per liter of water
in dilute body fluids the terms can be used interchangeably
What is the equation for Plasma Osmolarity? What three things do you need?
Plasma Na+, Glucose, Blood Urea Nitrogen (BUN)
Plasma Osmolarity = 2 x Plasma Na+ + (Glucose/18) + (BUN/2.8)
What is normal plasma osmolarity? What occurs if it is above this?
~290-300 mOsm/L
plasma osmolarity is too high–> and stimulate ADH and keep more water
T/F. Plasma Osmolarity (ECF) = intracellular osmolarity (ICF)
true, must be balance
If a cell is placed in an Isotonic Solution, what happens? What are two examples of an isotonic solution?
the cell won’t shrink or swell
290 mOsm/L
0.9% NaCl solution
5% glucose solution
What does it mean when intercellular and extracellular fluids are in osmotic equilibrium?
Isotonic solution
What is a solution called that has a lower concentration of impermeant solutes than the cell? What happens to the cell? What are examples of this?
Hypotonic solution (so less than 290 mOsm/L)
water will move INTO the cell –> cell swells and may rupture
Ex: less than 0.9% NaCl solution
Ex: less than 5% glucose solution
Ex: Freshwater
What is a solution with a higher concentration of impermeant solutes than the cell? What happens to the cell? What are examples of this?
Hypertonic fluid (greater than 290 mOsm/L)
water will move OUT of cell–> cell will shrink
Ex: more than 0.9% NaCl solution
Ex: more than 5% glucose solution
Ex: salt water
In the following, how does osmolarity compare?
- Isomotic solutions
- Hyperosmotic solution
- Hyposmotic solution
- osmolarity = cell
- osmolarity > normal ECF
- osmolarity < normal ECF
What will cause an increase in the cellular volume? What will decrease it?
increase:
- ingestion of fluid (water)
- intravenous infusion
decrease:
- not ingesting adequate fluids
- loss of fluids from GI tract
- sweating
- fluid loss from kidneys
What is the most common electrolyte disorder? What can this result in?
Hyponatremia (now plasma Na+)
edema, brain swelling, brain damage, death
(rapid correction can also cause damage)
What does Hyponatremia mean?
plasma sodium is low
What are normal levels of plasma Na+? How can one get Hyponatremia?
Normal levels of Na+ = 135-145 meq/L
via:
- dehydration (via loss of sodium chloride)
- overhydration (over retention of water)