ICPP Resting Membrane Potential Flashcards
What is a membrane potential?
The difference in electrical charge across the plasma membrane (intracellular vs extracellular)
How is membrane potential measured?
Fine microelectrode which can penetrate cell membrane without damage
Filled with conducting solution
In milivolts mV
Resting membrane potential of cardiac ventricular + atrial myocytes
-85mV
Resting membrane potential of neurones
-70mV
Resting membrane potential of skeletal muscle myocytes
-90mV
Resting membrane potential of smooth muscle myocytes
-50mV
What is the resting membrane potential?
The membrane potential between action potentials
Stay relatively constant
What are the two concepts of how resting membrane potentials are generated in cell?
1- biological membranes are selectively permeable to ions
2- the relationship between electrochemical gradients and equilibrium potentials
What to things are needed to generate membrane potential in relation to the membrane?
Membrane that is selectively permeable to ions
Concentration gradient for the ion
When is there no net movement of ions?
When the electrochemical gradient is 0 - the chemical gradient is at equilibrium with the electrical gradient
What is the membrane potential called when there is no net movement of ions?
What can it be calculated by?
Equilibrium potential
By the Nernst equation
What does the Nernst equation allow you to calculate?
The equilibrium potential
What is valency of an ion?
Its charge
Give 3 properties of ion channels
- selectivity for 1 or few species
- gating - pore opens or closes by conformational change in protein
- rapid ion flow - always down electrochemical gradient
How does the resting membrane potential arise?
- open K + channels dominate membrane ionic permeability at rest
- K+ diffuses down conc gradient out of cell + down electrical gradient into cell until equilibrium potential is reached
- resulting in a negative membrane potential inside cell of -95mV
