Resting Membrane Potential Flashcards
In which direction is the membrane potential defined?
The inside compared to the outside of the cell.
What is the standard unit for membrane potential?
millivolts
How can ions move through a membrane?
They cannot diffuse and so the only way is through ion channels.
List three properties of ion channels.
Selective, gated and allow rapid ion flow (when open)
What is selective permeability?
This is the fact that the cell membrane is permeable to different ions depending on the different ion channels which are open.
What ion is most responsible for setting up the resting membrane potential?
K+. It achieves this because there is an outward concentration gradient and an inward electrical gradient and so ions flow until these are equal and opposite.
What is the use of the Nerst equation?
This allows us to calculate Ek or E for any ion which is the membrane potential if it is only permeable to that specific ion.
Why is the resting membrane potential not equal to Ek?
There is a small leak of Na and Ca back into the cell.
What is the resting membrane potential in cardiac muscle?
-80mV
What cell type has a resting membrane potential of -70mV?
Nerve cells
What is the resting membrane potential of skeletal muscle?
-90mV
What is the resting membrane potential in smooth muscle cells?
-50mV
Define depolarisation.
This is a decrease in the size of the membrane potential (so it moves closer to 0)
What is repolarisation?
This is when the membrane potentIal becomes more negative and moves further away from threshold.
Opening of which ion channels leads to hyperpolarisation?
Cl- and K+
What ion channels need to open for a cell to depolarise?
Na+ and Ca2+
Can channels allow more than one ion to pass through?
Yes. Nicotinic acetylcholine receptors are permeable to both Na+ and Ca2+. They do not allow anions to move through.
Name three types of gating ion channels can exhibit.
Ligand gating, mechanical gating and voltage gating.
What is synaptic transmission?
This is where a chemical transmitter is released from the pre synaptic cells and binds to receptors on the post synaptic membrane.
What is fast synaptic transmission?
The receptor protein is an ion channel which opens when the transmitter binds.
What happens at an excitatory synapse?
At these synapses, binding of the transmitter opens ion channels which cause depolarisation of the membrane. More transmitter leads to a greater response.
What is the exciting post synaptic potential?
This is the change in potential of the post synaptic cell caused by the binding of transmitter and opening of ion channels.
When a synaptic transmitter binds to a receptor which opens Cl- or K+ channels, what type of synapse is this?
Inhibitory as it leads to hyperpolarisation of the membrane and the potential moves further away from threshold.
Give two examples of transmitters which act at inhibitory synapses
A-aminobutyric acid and glycine
What is slow synaptic transmission?
This involves a messenger molecule (G protein) as the ion channel and the receptor are different molecules.
Give two examples of slow synaptic transmission.
Direct G protein gating and gating via an intracellular messenger
What is gating via an intracellular messenger?
This is where when the transmitter binds to the receptor this activates the G protein. This binds to enzymes which produces a signalling cascade and the the messenger binds to the channel or activates PKA which phosphorylates the channel.
What is the difference in effect between direct G protein gating and gating via an intracellular messenger?
Direct G protein gating is a more localised effect whereas intercellular messengers affect the whole cell.
What is the role of Na+/K+ ATPase in the membrane potential?
It has a very minor role and may add a few mV to the membrane potential.
