0208101330 - Mfm Ii - Membrane Physiology (Fitzovich)

Front 1

In all cells what is the EC:IC relative charge?

Back 1

IC is relatively negative. this is referred to as the "membrane potential." this potential is caused by the unequal distribution of free ions.

Front 2

What is depolarization?

Back 2

any change that makes IC less negative relative to the resting membrane potential. the IC:EC charge is becoming less polarized.

Front 3

What is hyperpolarization?

Back 3

any change that makes IC more negative relative to the resting membrane potential. the IC:EC charge is becoming greater polarized.

Front 4

*What two conditions determine the membrane potential?*

Back 4

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

Front 5

Why does high conductance of an ion translate to high importance of that ion in membrane potential?

Back 5

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

Front 6

What is the difference between "potential difference" and "electrochemical potential difference?"

Back 6

1. potential = influenced by just the electrical force
2. electrochemical = influenced by electrical and chemical forces

Front 7

What is the "equilibrium potential" for any ion?

Back 7

The electrical potential needed to couteract the chemical potential for a given situation.

Front 8

What conditions must be met to get a passive membrane potential?

Back 8

1. selectively permeable membrane
2. impermeant ion - cation Na EC, anion proteins IC
3. permeant ion - K and Cl IC and EC

Front 9

What is important to know about the Nernst Equation and how is it used?

Back 9

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)

Front 10

What is the EK for Na, K, and Cl? And what is Em?

Back 10

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

Front 11

How do you calculate and interpret net force?

Back 11

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

Front 12

What prevents cells potential from being distorted by osmosis?

Back 12

active transport that corrects conductance leakage.

Front 13

What practical information is important to understand from the Chord Conductance Equation?

Back 13

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.

Front 14

What are the common conductances (g) for K, Cl, Na?

Back 14

gK = 0.9
gCl = 0.09
gNa = 0.01

Front 15

What functionally occurs when a cell's conductance for an ion increases?

Back 15

the membrane potential Em moves toward but does not exceed the equilibrium potential for that ion.

Front 16

How many Na and K are moved in what direction with a Na/K pump?

Back 16

2K are moved into the cell for every 3Na moved out, producing a net negative charge, negative inside relative outside

Front 17

What stimulates Na/K pump action?

Back 17

detection of intracellular Na