Exam #1: 2015 Flashcards
______ is the only neurotransmitter that is utilized at the neuromus-cular junction.
ACh is the only neurotransmitter that is utilized at the neuromuscular junction.
What elicits an action potential in a skeletal muscle fiber?
Depolarization of the motor end-plate (NO AP AT THE ACTUAL END-PLATE)
What is Intracellular Fluid (ICF)? What fraction of tbw is it?
Water within the cells. 2/3 TBW.
What is extracellular fluid? What fraction of TBW is it?
Water outside of cells. 1/3 TBW.
What is interstitial fluid, where is it found, and what forces create it? What fraction of TBW?
The fluid that actually bathes the cells. It is an ultrafiltrate of plasma (no proteins b/c they can’t cross capillary wall). It is created by the hydrostatic of the capillaries.
It is 3/4 of ECF and, thus, it is 1/4 of TBW
What is plasma, where is it found, and what forces create it? What fraction of TBW?
Plasma is the fluid circulating in blood vessels created by osmotic pressure. It is 1/4 of the ECF and, thus, 1/12 of TBW
Moles represent what?
The NUMBER of PARTICLES.
Osmoles represent what?
The number of particles into which a solute dissociates in solution.
Three moles of CaCl2 = ____ Osmoles?
9 osmoles, b/c 1 moles of CaCl2 = 3 osmoles (1 Ca + 2 Cl)
What is osmolarity?
The concentration of particles in solution expressed as OSMOLES per LITER (or other unit volume, e.g. Milliosmoles = osmoles per milliliter).
If a solute dissociates into more than one particle in solution, then its osmolarity equals…
The molarity (i.e. amount per volume —mol/L, mmol/L, etc.) X the number of particles in solution (its # of osmoles).
What is the osmolarity of a solution containing 6 mmol/L of CaCl2?
18 mOsm/L, because CaCl2 dissociates into three particles.
What is the distribution of TBW in men and women?
Men = 60% Women = 50%
What are the three typical ways AMOUNTS of a solute are expressed and what do they mean?
- Moles: Number of MOLECULES.
- Equivalents: The amount of charged (ionized) solute; the # of moles of solute X its valence (e.g. 1 mole of CaCl2 = 2 Eq of calcium, and 2 Eq of Cl).
- Osmoles: Number of particles in solution.
A CaCl2 concentration of 6 mmol/L corresponds to ____ mEq/L?
24 mEq/L
Define the principle of electroneutrality. How does membrane potential affect this?
Each bodily fluid compartment must have the same concentration (in mEq/L) of cations and anions. There can be no more cations than anions, or vice versa.
Membrane potential does not affect the BULK solution, because the separation of charges occurs only in the small area directly adjacent to the cell membrane. This small separation of charges is not enough to appreciably change the overall concentrations.
Given the difference in individual solute concentrations between the ICF and ECF, what keeps the total solute concentration (osmolarity) the same?
Water flowing freely across the membranes. Any transient differences in osmolarity are quickly dissipated by water movement.
What are the three most notable individual solute concentration differences between the ECF and ICF?
K+, Na+, and Ca2+ (!!!!!!)
ECF: K+ = 4, Na+ = 140, Ca2+ = 2.5
ICF: K+ = 120, Na+ = 14, Ca2+ = 0.0001 (!!!!!!)
What is the relative difference in pH between ECF and ICF?
ICF (pH 7.1) is slightly more acidic than ECF (pH 7.4)
- Define partition coefficient (K) and give equation.
- Describe what increases/decreases ‘K’
- Describe the partition coefficient for polar vs nonpolar molecules.
-The partition coefficient, by definition, describes the solubility of a solute in oil relative to its solubility in water.
K = (concentration in olive oil)/(concentration in water) –
- The greater the relative solubility in oil, the higher the partition coefficient and the more easily the solute can dissolve in the cell membrane’s lipid bilayer.
- Nonpolar solutes tend to be soluble in oil and have high values for partition coefficient, whereas polar solutes tend to be insoluble in oil and have low values for partition coefficient.
- Define diffusion coefficient, give its equation and define the terms.
- What does diffusion coefficient correlate with?
-Describes how readily a molecule will diffuse across a membrane — D= KT/6πrη, where: D = Diffusion coefficient, T = absolute temperature (Kelvin), r = molecular radius, and n = viscosity of medium. K is Bolztmann’s constant.
- Correlations are apparent in the formula.
p. 7
To calculate osmolarity, it is necessary to know the _____ of solute, and whether ________.
- concentration
- the solute dissociates in solution.
p. 12
Give the equation for osmolarity and define the variables
Osmolarity = g C – where: Osmolarity = Concentration of particles (mOsm/L) g = Number of particles per mole in solution (Osm/mol) C = Concentration (mmol/L)
Give the definition of osmolality
The concentration of osmotically active particles, expressed as osmoles (or milliosmoles) PER KG of water (as opposed to osmolarity, which is PER LITER).