Membrane Potential Transduction of signals at the cellular level Resting Membrane Potential Action...
-
Upload
ruby-barnhouse -
Category
Documents
-
view
235 -
download
4
Transcript of Membrane Potential Transduction of signals at the cellular level Resting Membrane Potential Action...
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