Resting Membrane Potential 3+4

Which 4 ions are found in greater amounts in the extracellular env? What is the net charge of the extracellular env?

Which 4 ions are found in greater amounts in teh intracellular env? What is the net charge of the extracellular env?

What are the two primary contributers of the electrochemical gradient?
 ( ) and   ( ) (intra or extracellular?)

Resting potentioal is between   and  and is always  

The extracellular potential is   and the intracellular potential is  

Resting membrane potential is also called

What is the formula for membrane potential?

Movement depends on cencentration   or   gradient (they can be in equal or opposite directions)

Electrical equilibrium is called  

When there is NO more movement of an ion even if there is a favoring gradient
because it has reached  with its forces. Equilibrium with its   and   potential. The   equation explains this relationship.

If Ena for sodium is 61+ mV, what does that mean?

For sodium,  and   gradident botth drive sodium into the the cell.

For potassium,   drives potassium  but a much larger   drives potassium  . Vector addtion, so leaves.

Equilibrium potential is 

Em is due to high resting conductance to K+ at rest when Na + channels are closed because the sodium channel is “ ”, if it is too negative it  .

Em is maintained by the  

The cell takes advantage of this and switches the cell on “depolarizes” the cell by
letting   in and switches it off “repolarize” by removing positive charges in the
form of  

Driving force is the   minus the  

Cells in different tissues have different  

Membrane potential:   potential that exists across the cell membrane.

• Resting membrane potential or resting potential (EM):  
across the membrane of a cell at rest.

Equilibrium potential (EX): membrane potential at which there is   ion
movement in or out of the cell ; it is the value of the potential difference across the
membrane when an ion is in electrochemical equilibrium

Electrochemical Equilibrium (EX): when the electrical & chemical forces inside
and outside the cell have  each other out resulting in no net movement
of an ion

• Excitability: a function of the plasma membrane mediated by   in
state of transmembrane proteins termed ion channels or pores

Selective permeability is highest for  
 >>> > 

In all cells, Vm is close to Ek but more
 than Ek

Why isn't the volage membrane potential equal to potassium's equilibrium potential?

Potassium allows  to leak  

Sodium is the  , K+ is the  

Recall that cells are “polarized” with
a negative resting membrane
potential   in a typical cell

  is the process where
the membrane potential is now
becoming positive (no longer at
rest), away from the “polarized”
state hence “de” In a typical cell this happens with a
sodium  influx

During depolarization, potential difference between inside and outside 

This is a process where the
“polarized” cell returns to its
polar state 

Resting membrane potential is
restored and the potential
difference across  
its  

This is a process where the
“polarized” cell becomes too
negative  

Majority of cell types in the
body needs to go through
 so ion
channels recover, a break
before the next wave

GHK equation predicts a reversal potential that is
equal to the  potential

Ionic currents measured with  

Hyperkalemia is a common clinical problem that is most often due to impaired
  due to acute or chronic kidney disease and/or
disorders or drugs that inhibit the   axis.

Hypokalemia is the result from unreplenished  or   due, for
example, to  ,  , or  therapy,  

In hypokalemia, , a reduction in the serum (extracellular) potassium will
  the cell membrane (that is, make the membrane potential more
electronegative); this impairs the ability of the muscle to   and
 , leading to weakness.

Symptoms of hypokalemia do not manifest unit below  

 : membrane potential that triggers an action potential; it
could be caused by passive propagations.

  a rapid all or none change in membrane potential, followed
by a return to the resting membrane potential; require voltage gate ion channels.

  causes the membrane potential to become more positive
(decreases EM)

  causes the membrane potential to become more
negative (increases EM).

  is caused by neurotransmitters/stimulus on postsynaptic
membrane

What are the stages of theaction potential of a neuron?
1. Resting membrane potential is  .
2. Depolzarization occurs ( )
3. Repolarization ( )
4. Afterhyperpolarization ( )

In order to be stimulated, a neurotransmiter release causes opening of Na+ channels and Em is more positive ( mV)

Opening of sodium channels can be “timed” appropriately called “ ” or if sodium channels are close to each other “ ”

Having a threshold means the cells will not depolarize without a stimulus – this
is termed an   phenomenon

Depolarization, in a nerve cell it is split into two  and  -  
enters in both phases. Rising phase occurs until potential is  . Overshoot is above 

Sodium channels have two gates activation
gate ( ) and the inactivation gate ( )

The inactivation period of the sodium channel
is what is termed the “ 

When some sodium channels recover from the
inactivation state, this is termed “ ”

At the peak of the action potential,   channels open (and   channels closed) (they are voltage gated)
Because   channels are inactivated, rapid repolarization takes place

d Na/K ATPase pump restores  

 is a
property of a
channel, how many
ions are allowed
through which
depends on how
much the channel
pore opens

  propogation - graded signal that dimimishes with distances and will not transport sinal from one end of axon to the other

  propagation - the action potential has constant velocity and not change in a,plutide and vaires over time. Strong enough to reactivate itself.

The probability of a channel being in
an open state, or a closed state
depends on  

  are triggered by the inactivation of sodium channel.

Refractory periods determine   and are responsible for  and   propagation for origin of inital segment

Absolute:
• Another AP   occur
regardless of the  
• All Na+ channels are  

Relative:
• Another AP  occur if the
stimulus is  than normal
• Some Na+ channels are
beginning to recover from
inactivation

Opening of voltage gated Na+ channels (Nav) has a  , as
ion channels open and Na+ enters the cell, it becomes more (+) & more ion channels open. At threshold they all  

Depolarization opens voltage gated   (  rectifier K
+) much slower kinetics. Works like a  that opposes the effect of depolarization Nav