Session 4 (Resting Membrane Potential + Changing The Membrane Potential) Flashcards
What is membrane potential?
The magnitude of an electrical charge that exists across a plasma membrane
What is used to measure a membrane potential?
A glass microelectromechanical (pipette)
What do you fill your glass pipette with when measuring membrane potentials?
A conducting solution (ie KCl)
What causes a membrane potential to be set up?
The membranes selective permeability
How is a membrane potential set up?
At rest K+ channels are open, allowing K+ to flow OUT (down its conc gradient), other anions (-ive ions) cannot follow.
-ive charge builds up inside cell, K+ therefore don’t want to leave as much and a equilibrium is reached.
K+ wants to leave because of conc gradient but wants to stay because of electrical gradient
What is Ex?
The equilibrium potential of a given ion (x)
What does z mean in the following equation?:
Ex=61/Z.log([x]o/[x]i)
Z means valency (charge on ion)
If a membrane potential is set up as a result of K+ ions moving, why is the membrane potential not -95mV, which is Ek?
Because the membrane is not perfectly selectable for K+ ions, some other channels are open.
What happens if [K+]o increases?
[x]o means concentration of ion outside of cell
Ek becomes more positive therefore membrane potential becomes more positive
What will opening Na+ and/or Ca2+ channels do?
Depolarise cell
What will opening K+/Cl- channels do?
Hyperpolarise cell (or repolarise, depending on the context)
What is Px?
The relative permeability coefficient for each of a given ion (x)
What underlies the overall selectively of a cell membrane?
The number of open channels of different types (eg ligand/voltage/mechanical)
What channels are used for fast synaptic transmission?
Ligand gated ion channels
What do depolarising transmitters cause?
Excitatory postsynaptic potentials (EPSP)
Name an excitatory transmitter (3)
ACh, Glutamate, Dopamine
Name an inhibitory transmitter (2)
Glycine, GABA
What do hyper-polarising transmitters cause?
Inhibitory post synaptic potentials (IPSP)
Why is slow synaptic transmission slow?
Because the receptors and the channels are separate proteins
Give an example of a protein receptor involved in slow synaptic transmission
GPCRs
What are the 2 types of slow synaptic transmission that involve a GPCR? Explain the methods
Direct G protein gating (receptor caused G protein to activate channel- localised and quite rapid)
Gating via an intracellular messenger (GPCR activates enzymes involved in signalling cascade, secondary messenger activates channel- throughout cell, amplification by cascade)
Define ‘hyperpolarising’
An increase in the size of the membrane potential from its normal value (cell interior becomes more negative)
Define ‘depolarising’
A decreasing of the size of the membrane potential from its normal value (cell interior becomes less negative)
What changes membrane potentials?
Changes in activity of ion channels
