L2 - RMP Flashcards
What is conductance? What does it tell you about the neuron?
Inverse of resistance. Tells you whether a channel is opened or closed. Fully open = full conductance = 1 on the graph.
Na+, Cl-, K+, Ca 2+ - Which ones are highest extracellularly?
Na+ Cl- Ca2+
Difference b/n ion conc of squid and mammalian neuron?
Squid neuron is not myelinated -> wider axon -> higher ion conc
Function of Na+/K+ ATPase? How many subunits?
Moves 2K+ inside and 3Na+ outside (goes against conc gradient)
2, alpha and beta
Oubain binding site of Na+/K+ ATPase
Poison in high conc. Treatment for cardiac rhythmia.
Function of Ca2+ pump
Moves H+ inside and Ca2+ outside
T/F: At rest the neuronal membrane is selectively permeable to K+
T
2 Factors determining RMP
Ion conc gradients and hence ion pumps and permeability to K+
Explain the selectivity of K+ for K+ channels and how other ions can’t enter it
Oxygen molecules of the amino groups on the selectivity pore are spaced identically (nearly) to how it would be spaced if K+ was surround by water molecules - a relaxed, low E config where one K+ enters after another. Na+ is not relaxed in this config., hence cannot enter.
Three types of gates
Voltage, ligand (extracellularly but also intracellularly via second messenger molecules), mechanically-gated (in response to deformation of the skin, they open and depol neuron that provide that sensation e.g. sensory afferents)
Gating Hinge?
In response to opening of channel, structure moves around hinge to open/close so selectivity filter (pore) is still in the same place.
What two K+ channels are important for RMP
Inward rectifier, 2-pore
K+ voltage-gated and HERG
6 transmembrane spanning domains per subunit – 4/5 subunits make a pore
Inward rectifier – major role in determining RMP
2 pores in a loop, changes property as voltage changes
Ca2+ activated
Multiple transmembrane domains
