Lesson 1-2 Flashcards
Water determines the structure and biological properties of:
Proteins, Nucleid acids, Lipids, biological membrane
Water has a tendency to inoize into?
Ionize into hydrogen and hydroxyde ions. This ionization is crucial to waters role in cellular function. The amount of hydrogen and hydroxide ion in a solution is: (H+) x (OH-) = 10^-14 mol/l
pH in water?
- In pure water, there is one hydrogen ion for every hydroxide ions, so they are both equal 10^-7 mol/l. - as pH = -log (H+), in pure water pH =7
Claude Bernard stated:
Life is an expression of the physical reality and the maintenance of life is guaranteed by the constancy of the fluid matrix or “milieu interieur”
Walter Bradford Cannon stated:
Stability of internal environment = Homeostasis
Fluid compartments in the Body:
Total Body Fluid:
- Intracellular fluid (ICF)
- Extracellular Fluid (ECF):
- Interstitial fluid (ISF), Intravasal fluid (IVF), Trancellular fluid (TCF)
Intracellular fluid
Comprises 2/3 of the bodys water. It is primarly a solution of potassium and organic anions, proteins etc. The cell membranes and cellular metabolism control the constituents of this ICF.
Extracellular fluid (ECF)
Is 1/3 of the bodys water. ECf is primarly NaCl and NaHCO3 solution. It is further subdivided into: - Interstitial fluid (surrounds the cells, but does not circulate. 3/4 of ECF) - Intravasal fluid IVS (blood plasma, circulates as the extracellular components of blood. 1/4 of ECF) - Transcellular fluid TCF (set of fluid that are outside of the normal compartments, 1-2%. Cerebrospinal fluid in the CNS, aqueous humor and vitreous humor, synovial fluid in the joints, glandular secretion, serous fluid etc)
Components of homeostasis
Isovolemia, isosmosis, isoinoia, isohydria
Isovolemia =
The constancy of the volume of ECF
dehydration =
decreased volume of ECT, less than 20%
overhydration =
Increased volume of ECF, more than 20%
hypovoloemia=
decreasedvolume of blood plasma
hypervolemia=
increased volume of blood plasma
oedema=
increased volume of ISF
Isosmosis =
The constancy of the osmotic pressure of ECF
Osmotic pressure depends on?
the number of solute particles per unit volume = osmotic concentration (osmolarity)
Difference between Isosmotic and Isotonic?
For an isosmotic solution to be isotonic, the membrane must be equally impermeable to all solutes. - All isotonic solution are isosmotic! - But not all isosmotic solutions are isotonic!
Isohydria =
The constancy of the pH of ECF
pH of ECF=
7.4
pH in blood =
-log 2.5 x 10^-7 = 7.4 (7.35-7.45)
pH is acidosis when?
it is between 7.35-7.0
pH is alkalosis when?
it is between 7.45 and 7.8
Acid-base balance is regulated by:
Acid-base buffer systems, respiratory centers in the brain ste and the kidneys
Buffer systems or buffer pairs tend to….?
reisits change in pH, when H+ or OH- is added
What is buffer capacity?
it is a measure of the efficiency of a buffer in resting changes in pH. Conventionally, the buffer capcaity is expressed as the amount (mol) of strong acid or base, that must be added to 1 liter of the solution to change its pH by one unit.
Bicarbonate buffer system:
mainly in ECF
Phosphate buffer system:
Mainly in ICF
Protein buffer system:
in plasma and ICF
Hemoglobin buffer system:
Henderson-Hasselbalch equation
