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17 Cards in this Set

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  • Back
In all cells what is the EC:IC relative charge?
IC is relatively negative. this is referred to as the "membrane potential." this potential is caused by the unequal distribution of free ions.
What is depolarization?
any change that makes IC less negative relative to the resting membrane potential. the IC:EC charge is becoming less polarized.
What is hyperpolarization?
any change that makes IC more negative relative to the resting membrane potential. the IC:EC charge is becoming greater polarized.
*What two conditions determine the membrane potential?*
1. slow process of concentration ratio of free ions
2. fast process of permeability of the membrane to different ion, which determines the membrane conductance
Why does high conductance of an ion translate to high importance of that ion in membrane potential?
because as a result, that ion can move to the other side of the membrane at a certain rate to make a change in potential
What is the difference between "potential difference" and "electrochemical potential difference?"
1. potential = influenced by just the electrical force
2. electrochemical = influenced by electrical and chemical forces
What is the "equilibrium potential" for any ion?
The electrical potential needed to couteract the chemical potential for a given situation.
What conditions must be met to get a passive membrane potential?
1. selectively permeable membrane
2. impermeant ion - cation Na EC, anion proteins IC
3. permeant ion - K and Cl IC and EC
What is important to know about the Nernst Equation and how is it used?
this equation produces the equilibrium potential for any given ion, X. this is the potential needed for X to be in equilibrium.
1. As [X]EC/[X]IC increases, the larger the equilibrium goes.
2. as the electrical charge of the ion increases, the equilibrium potential decreases.

If you know what the resting membrane potential is and you know the equilibrium potential for X and it's behavior about that membrane, then you know how X will behave.

EK = -(RT/Z)*ln([X]IC/[X]EC)
What is the EK for Na, K, and Cl? And what is Em?
Na = 64.8 mV (is a cation)
K = -92 mV (is a cation)
Cl = -78.1 mV (is an anion, btw)

notice K >> in IC, Na >> in EC, Cl >> in EC

Em = -70 mV
How do you calculate and interpret net force?
calculate = NF = Em - EK
for cations: -NF pulls ions into cell
for anions: -NF pulls ions out of cell
for cations: +NF pulls ions out of the cell
for anions: +NF pulls ions into the cell
What prevents cells potential from being distorted by osmosis?
active transport that corrects conductance leakage.
What practical information is important to understand from the Chord Conductance Equation?
Em = [gK/sum(g)]EK + [gNa/sum(g)]ENa + [gCl/sum(g)]ECl

g = conductance

this means that Em directly depends on the equilibrium potential for major ion players times a factor that represents how big of an effect they will have based on the permeability/conductance of that membrane.

K plays a big role because gNa is close to zero and gCl is small so the biggest changes occur when K's contribution changes like when the cell's g for an ion changes.
What are the common conductances (g) for K, Cl, Na?
gK = 0.9
gCl = 0.09
gNa = 0.01
What functionally occurs when a cell's conductance for an ion increases?
the membrane potential Em moves toward but does not exceed the equilibrium potential for that ion.
How many Na and K are moved in what direction with a Na/K pump?
2K are moved into the cell for every 3Na moved out, producing a net negative charge, negative inside relative outside
What stimulates Na/K pump action?
detection of intracellular Na