Lecture 3 & 4 - Memb/action Potentials Flashcards
Resting membrane potential that we will use for physiological purposes?
-90 mEv
saltatory conductions occurs in which part of the neuron?
axon
resting membrane potential eqn?
EMF = Eion = z(61.5) x log ([ion]outside/[ion]inside)
Dendrites conduct what type of potentials?
Local potentials
Cell bodies of neurons typically conduct __________ potentials, rather than ______ potentials?
Local
Action
what type of protein channels are dendrites known for having ?
Ligand gated ion channels
What is the plasma memb. of an axon called? and what protein channels does it contain?
Plasmolemma
Voltage gated ion channels
•A diffusion potential is caused by ?
an ion concentration difference on either side of a membrane
resting potentials always negative b/c ?
they are taken from INSIDE the cell
•The Nernst potential is ?
the diffusion potential level across a membrane that exactly opposes the net diffusion of a
particular ion through the membrane;
Eqn for the nernst potential?
what is it used for ?
E = 2.3 RT/F log Co/Ci
EMF = Eion = z(61.5) x log ([ion]outside/[ion]inside)
-z if Cl ion, + of K or Na ion.
measures the potential for one ion at a time.
Diffusion potential =
the EMF electro motive force
resting memb. potentials in nerves for
Na?
K?
+70 mV
-94 mV
What does goldman equation get us?
What is the actual potential and why?
the calculated memb. potential on the inside of the cell of -86 mV
With the Na/K pump it takes our resting potential to -90.
what are the 2 potentials to be balanced in the Nernst Eqn?
Osmolarity potential and Electric potential
What is the difference in channels b/w action and local potentials?
Local have ligand gated and Action pot’s have ion gated.
how many gates in K and Na ion gated channels? when open
K - 1 gate open from +30mV to -90mV
Na - 2, activation and inactivation gate
activation open from -70to -50 and stay open until -90 but
Inactivation closed from +35 to -90
What is responsible for forming the selectivity filters on the K ion channels?
Carbonyl oxygens bound to the poor helix.
larger diameters of axons =
less resistance and therefore faster action potential
myelin sheaths act like ? to insulate and keep charges separate.
Capacitors
Threshold .
is the point at which a local potential will elicit an action potential
typically -65 mV
Direction of Action Potentials, 2 ways? and why more one than the other?
Orthodromic - normal direction , down axon away from soma
Antidromic - opposite direction.
Ortho more b/c of Refractory periods, and ion gated channels need a moment to reset.
Do all axons contain schwann cells? what does this mean or not mean?
Yes they all have schwann cells, though it doesn’t mean that they all contain myleinated sheaths, B/c they don’t.
•_________ is the principle lipid found in myelin sheaths.
Sphingomyelin
Which are fastest neurons?
Large myelinated nerves
