LMP301 Lecture 3: Fluid Balance Flashcards
How much ICF is there?
28L
ECF can be subdivided into…
- Plasma
- Interstitial fluid (ISF)
How much ECF is there?
14L
How much plasma is there?
3.5L
How much ISF is there?
10.5L
ACE inhibitor = ?
angiotensin converting enzyme inhibitor
What are ACE inhibitors used for and how do they work?
Used for hypertension
Work by dilating blood vessels
What are the common electrolytes measured?
Na+ K+ Bicarbonate Ca++ Potassium phosphate
Where are electrolytes measured from?
Plasma
Plasma and electrolytes are most abundant in…
ICF
Is it harder to do ECF or ICF measurement?
ICF
What are extracellular ions?
Na+
Cl-
HCO3-
Ca++
What are intracellular ions?
K+
PO4
Anions
Define: concentration
amount of solute in a solvent
Define: osmolality
amount of solute particles in a solvent (weight)
mmol/kg
mOsm/kg
How to estimate osmolality?
Measure the most abundant solutes:
2[Na+] & [Glucose] & [Urea]
Define: osmolarity
amount of solute particles in 1kg of water (WATER IS SOLVENT)
When measuring dilute aqueous solutions, the appropriate unit is…concentration / osmolality / osmolarity
osmolarity
One weakness of concentration measurements
Must take into account total volume of solvent (dehydrated might affect measurement of electrolytes)
Osmolarity is a passive / active process?
passive
Define: oncotic pressure
Pressure in the capillaries
Walls of capillaries act as semi-permeable membrane, and proteins pull water into plasma.
Define: hydrostatic pressure
Pressure exerted by the heart when it pumps
Pushes fluid in vessels into ISF.
Oncotic pressure is balanced by…
Hydrostatic pressure
Hydrostatic pressure is balanced by…
Oncotic pressure
What might affect oncotic pressure?
- Injury: cause proteins in plasma to leak out
Typical input of water?
0.5 - 5L per day
Amount of output of water through renal processes?
0.5 - 4L per day
Amount of output of water through GI tract?
< 0.1 L per day
Amount of output of water through insensible loss?
0.5 - 1L per day
Define: insensible loss
Loss of fluid through sweat & respiration
Most of body fluids are lost through…
Renal processes (kidney)
Define: dehydration
Releasing more fluid than you’re consuming
Define: overhydration
Taking in more fluid than you’re releasing
Define: polyuria
A lot of pee
Define: polydipsia
Consuming a lot of water
Define: oligouria
Small amount of urine output
Define: anuria
no urine output
What medical term falls under dehydration?
polyuria
What medical terms fall under overhydration?
- polydipsia
- oligouria
- anuria
Features of dehydration (physical)
- increased pulse
- dry mucous membranes
- soft / sunken eyeballs
- decrease bld pressure
- decreased urine
- decreased skin turgor
Biochemical signs of dehydration
- increased plasma sodium
- increased bld urea
- increased hematocrit
Define: hematocrit
volume of RBC in blood
What is edema?
Accumulation of fluid in the ISF of your cells
Edema is a symptom of…
overhydration
Features of overhydration (physical)
- normal pulse
- normal mucous memb
- normal eyeballs
- normal / incr bld pressure
- normal / decr urine
- incr skin turgor
Symptoms of overhydration (biochem)?
- normal / decr plasma sodium
- normal / decr bld urea
- normal / decr hematocrit
How is water regulated in the body?
- Control osmolality
2. Control bld volume
Which is the direct route of water regulation?
control of osmolality
which is the indirect route of water regulation?
control of bld volume
How is osmolality controlled in the body? (via ADH)
- Hypothalamus senses bld osmolality
- Hypothalamus tells p. pituitary to make ADH
- ADH goes to kidney collecting tubules
- Kidney absorbs more water
more Na+ in the bld indicates… (in terms of osmolality)
higher bld osmolality
Less Na+ in the bld indicates ____ osmolality
lower
How is osmolality controlled in the body?
- ADH
2. Thirst
How is osmolality controlled in the body? (Thirst)
- Hypothalamus tells you to drink water
2. When homeostasis is reached, hypothalamus tells p. pituitary to stop secreting ADH