Resting Membrane Potential Flashcards
What is membrane potential?
The magnitude of an electrical charge existing across a plasma membrane
How is membrane potential always expressed?
The potential inside the cell relative to the extracellular solution (measured in mV)
Which cells have the largest resting membrane potentials?
Cardiac and skeletal muscle cells:
-80 to -95 mV
Which cells have the smallest resting membrane potential?
Erthyrocytes:
-9mV
What is the resting membrane potentials of nerve cells?
-50 to -75 mV
How can membrane potential be measured?
Voltmeter used
The microelectrode is a fine flass pipette - tip diameter is less than 1 micrometre
This can penetrate cell membrane without bursting cell
Filled with a conducting solution (KCl)
What are the two factors important for the generatio of membrane potential?
Ion concentration gradients and selective ion channels
What are the most important ion channels for most cells?
K+, Na+ and Cl-
What are ion channels?
Proteins that enable ions to cross cell membrane
What is the phospholipid bilayer permeable to?
Small uncharged molecules - oxygen, carbon dioxide, water, benzene
What is the phospholipid bilayer very impermeable to?
Charged molecules (ions
What will chloride channels also move?
Other halide ions
What are some properties of ion channels?
Selectivity for one or few ion species, pore opens/closes by conformational change and rapid ion flow down the electrochemical gradient
Are there more proteins inside or outside of the cell?
More proteins intracellularly which makes the inside of the cell more negatively charged
What are the intracellular and extracellular levels of K+?
Intracellular = 160 mM Extracellular = 4.5 mM
What are the intracellular and extracellular levels of Na+?
Intracellular = 10 mM Extracellular = 145 mM
What are the intracellular and extracellular levels of Cl-?
Intracellular = 3 mM Extracellular = 114 mM
What dominates the membrane ionic permeability at rest?
Open K+ channels
How does the resting membrane potential arise?
Because the membrane is selectively permeable to K+
What does the Nerst equation allow you to calculate?
Membrane potential at which K+ will be in equilibrium, given the extracellular and intracellular K+ concentrations
True or False:
If a membrane is selectively permeable to K+ alone, its membrane potential will be at Ek.
True
What is the Nerst equation?
Eion = 61/Z x log10 (ion out/ion in)
What would happen to the membrane potential if there was an increase in the permeability of the membrane to K+ ions?
K+ ions would move out of the cell so there will be a more negative intracellular charge and a more positive extracellular charge
Some neurotransmitters act to increase Cl- conductance in the postsynaptic cell. What are the consequences of this for the membrane potential?
An increase in Cl- inside the postsynaptic cell would make it more negative inside so it becomes a lot harder for the sodium ions to enter and depolarise the cell
