Membrane Potentials

The amount of ____increases with the quantity of charge and as distance of separation between charges decreases

FORCE

If psoitive and negative charges are separated, there is an ___potential driving the ions toward each other

Electrical

As the difference in charge across the battery ____the magnitude of the voltage (potential difference)_____

Increase; increases

If positive and negative charges are allowed to pass freely, the charges will move, creating an____

CURRENT

What kind of gradients do living cell generate?

electrochemical

Produced by non-equal distribution of charged particles (ions) in extracellular and intracellular fluids

Electrochemical gradient

small nonpolar molecules (O2, CO2)

Hydrophobic molecules (steroids)

Small uncharged POlar molecules (urea, glycerol)

Simple Diffusion

Glucose

Ions (Na+, K+, Ca2+)

Facilitated Diffusion

Na+/K-AtPase

Ca2+-ATPase

H+-ATPase

Active Transport

Can ions diffuse across a lipid membrane?

NO

What is ion movement across the lipid membrane regulated by?

Opening and closing of ion channels

When a neuron is not excited, the voltage across the plasma membrane is called the ____membrane potential (Think tired and very relaxed)

resting

By convention, extracellular fluid is assigned a voltage and intracellular fluid is based off of that. What is that voltage?

0, measured relative to that

What charge do intracellular and extracelllular have

Intracellular(INSIDE) is negatively charged

relative to the Extracellular (Outside)

Charged ions tend to collect tightly at the ____membrane

plasma

The hydrophobic membrane acts as a ____to separate the charges

Barrier

The bulk of extracellular and intracellular fluid has a____of charge

balance

What protein is responsible for maintaining the ionic difference between the ECF and ICF

THe NA+/K+ pump

Resting Membrane Potential

Requires ____(ATP)

How many Na+ are pumped out

How many K+ are pumped in

what is the net change in charge distribution

Is it electrogenic?

Energy

3

2

Inside becomes more negative than the outside

YES

Does the Na+/K+ pump always function?

yes, the ions don’t remain in place

Ions are in constant flux, flowing across cell membrane through open____

channels

counteracts the diffusion of ions through membrane channels for all living cells

maintains resting potential gradient

Active Pump

What type of energy form is required for the Na+/K+ pump?

ATP

The K+ Gradient

High K+ in ____and low K+ in _____. Both sides are neutral

The membrane is only permeable to ____

Ions diffuses from ____ to _____ due to concentration gradient

An excess of ___charges builds on the left

Some _____ions are now attarcted to the right

Intracellular, Extracellular

K+

right, left

positive

K+

The movement of of K+ ions is due to differences in both ________ and _______ across the membrane

concentration; charge

As long as the concentration flux (to the left) exceeds the electrical flux (to the right) in K+, charge differences will continue to build up

Eventually the concentration flux and the electrical flux will come to an ______

There is no net ____ of K+

equilibrium

movement

The membrane potential at which the electrical flux for K+ balances the concentration flux for K+

equilibrium potential

Equilibrium potential is determined by the magnitude of the K+ difference. The greater the concentration difference, the ____ the magnitude of the membrane potential must be to balance it

greater

Nernst Equation

E=61/(Charge) * log (CO-CI)

Calculated equilbrium potential for K+

-90mv

The Na+ gradient

Low Na+ ____; High NA+______. Both sides neutral

Membrane only permeable to ____

Na+ ions diffuse from ____to ___

The _____side gains positive charge

Na+ ions will now be attarcted to the ____

As long as concentration flux eceeds electrical flux, the potential difference will_____

An ___wil be reached

Intracellular, extracellular

Na+

left to right

right

left

increase

equilbrium potential for Na+

Calculated equilibrium potential for NA+ in an average cell

+60

___(-90_is high inside the cell while _____(60+) is high outside of the cell

K+, Na+

A cell at rest is permeable to both ___ and ___

K+ and Na+

The permeability of ____ is about 20-100 times larger than the ____ permeability due to the presence of _____leak channels

K+, Na+, K+

The resting membrane potential of cells is close to the______

K+ equilibrium potential

IF Na+/K+ ATPase completley stopped, what would be the resting membrane potential?

0

The voltage difference between the inside and outside of a cell

Memabrnae Potential

The voltage gradient potential across a membrane that is equal and opposite to the concentration force affecting a given ion type

Equilibrium potential

THe voltage difference between the inside and outside of a cell in the absence of excitatory or inhibitory stimulation

Resting membrane potential

Resting Membrane Potential Summary

Differences in the ____of specific ions across the cell membrane

Transmembrane concentration gradients are generated by active _____transporters

Membrane is selectively ____to some of the ions (K+)

concentration

Ion

permeable

The membrane potential becomes less negative than RMP

Depolarization

The membrane potential becomes positive

Overshoot

The membrane potential returns to its resting value

Repolarization

The membrane potential becomes more negative than the RMP (less than -70mV)

hyper polarization