Membrane Potential

Transduction of signals at the cellular level

Resting Membrane Potential

Action Potential

Why do we need to know about RMP and AP?

Transduction of signals at the cellular level

EPSPIPSP

Initial segment AP Ca2+ influx

Neurotransmitter

Neurotransmitter releasing

•Somatodendritic part – passive conduction of the signal, with decrement

Axon – the signal is carried without decrement

Preliminary knowledge

What is necessary to know beforehand

Cell membrane

Proteins peripheral

integral non penetrating

penetrating (transmembrane)

Phospholipid bilayer

Na+- K+ pump

Na+- K+ pumpExtrude 3 Na+ ions

Bring in 2 K+ ions

Unequal distribution of ions

Na+ and Cl - extracelullary

K+ a A- intracelullary

Ion channels in the cell membrane

Resting channels - normally openGated channels - closed when the membrane is at rest

» opening is regulated by» 1. Membrane potential (voltage gated)» 2. (chemicaly gated)» 3. Membrane potential plus ligand binding

(Voltage and chemicaly gated)» 4. Membrane stretch (mechanicaly gated)

voltage gated sodium channel

Resting membrane potential

Membrane potential is not a potential.

It is a difference of two potentials so it is a Voltage, in fact.

The unequal distribution of ionsNa+, Cl- are more concentrated

outside the cell

K+ , A- are more concentrated inside the cell

When the membrane would be permeable for K+ onlyChemical driving forceoutward movement of K+

K+

A-

Na+

Cl-

When the membrane would be permeable for K+ only

More positiv charges are outsideA- can not leave the cell

electrical driving force emergesinward movement of K+

When the membrane would be permeable for K+ only

Chemical driving forceelectrical driving forceelectrode can record a voltage=RESTING MEMBRANE POTENTIAL

Equilibrium potential for K+ and Na+

When the membrane would be permeable for K+ only

Ion distribution in the nerve fiber

The voltage can be discharged into surroundings

How to calculate the magnitude of the membrane potentialOsmotic workThe work, which must be done to move 1 mol of the

substance from concentration C1to concentration C2

Ao= R.T.ln [C1] /[C2 ]Electric work The work, which must be done to move 1 mol of the

substance across the potential difference E Ae = E. n. FR.T.ln [C1] /[C2 ] = E. n. FE =

How to calculate the magnitude of the membrane potential

Ao= Ae

R.T.ln [C1] /[C2 ] = E. n. F

E = Nernst equation

Goldman equation

Action potential

Membrane potential

Conductance of the membrane for Na+ and K+

Time segment when the AP cannot be elicited