Membrane Potentials Flashcards
(20 cards)
What is voltage difference?
Difference in charge between inside + outside of cell
What is membrane potential?
Voltage across plasma membrane=> gives ions the potential to move from one side to other
What is definition of resting potential?
Membrane potential of cell not sending signals
What is resting potential in neuronal cell?
-70mV
What is resting potential of cardiac cell?
-90mV
What occurs in formation of resting potential?
K+ channels are always open at resting potential
Inside the cell, [K+] is high and [Na+] is low
Outside the cell, [K+] is low and [Na+] is high
Na+ and K+ gradients are maintained by Na-k pump which is ATP driven, pumping 3 Na+ out and pumping 2 K+ ions in.
What is Nernst equation?
Considers membrane permeable to single ion Equilibrium potential (Eion) = 62mV (log[ion] outside / [ion] inside)
What is equilibrium potential of K+ ion?
-90mV
What is equilibrium potential of Na+ ion?
+62mV
What is Goldman equation?
Takes into account all the ions of the membrane
What is hyper polarisation?
Membrane potential becomes more negative
Gated potassium channels open, K+ ions diffuses our making the inside of cell more negative
What is depolarisation?
When gated sodium channels open, Na+ ions diffuses into cell, making inside of the cell more +ve
What are 5 stages of generation of action potential in neurones?
Resting state Depolarisation Rising phase of Action potential Falling phase of action potential Undershoot
What are 6 stages of generation of action potential in cardiac cell?
Diastole= voltage gated Na+ and K+ channels are closed Depolarisation Rapid Na+ inactivation Plateau phase Rapid repolarisation Diastole- closing of K+ channels
What are evolutionary adaptations of axon structure?
2 variables that control speed of AP travels is diameter of axon + myelination of axon
What are 2 different type of cells that myelin sheath is created depending upon whether axon is in either CNS or PNS?
Oligodendrocytes in CNS
Schwann cells in PNS
What is node of Ranvier?
Is where action potentials are formed
They are gaps in myelin sheath where voltage gated sodium channels are found
Action potentials in myelinated axons jump between nodes of Ranvier via….
Saltatory conduction
What do action potentials do?
In neuronal cell
In cardiac cell
APS can arrive either chemical or electrical synapse
In neuron: electrical signal -> chemical signal in synapse -> electrical signal
Cardiac cell-> don’t release transmitter. They are directly coupled to next cell by gap junction channel
What is gap junction channel?
Proteins that directly allow the systole of one cell to be connected to with systole of next cell. As result AP can flow from one cell to another quickly
