Neuronal Action Potentials Flashcards
action potential propagation
- propagated without degradation
propagation without degradation important for
- communication over long distances
conduction velocity of myelinated axons versus unmyelinated axons
- myelinated axons have a faster conduction velocity
conduction velocity of large-diameter axons
- faster conduction velocity than small diameter axons
the spatial distribution and density of specific types of ion channels influences
- the site of initiation of the action potentials
- the modulation of action potentials
all or none phenomenon
- once triggered, an action potential is a consistent amplitude and duration
what is the voltage required to get enough voltage to open or initiate the all-or-none behavior of the action potential
- threshold
a sub threshold stimulus fails to do what
- fire an action potential
small depolarizations due to
- opening of ligand gated or stimulus gated channels
if the depolarization is large enough
- then voltage gated Na+ channels open
depolarization phase on the graph
- upstroke
local depolarization causes opening of
- Na+ voltage gated channels
- Na+ influx
- full depolarization
overshoot on graph
- depolarization above 0 mV
repolarization on graph
- going from overshoot down toward resting potential
what happens during repolarization to the Na+ voltage gated channel
- will be inactivated
rate of sodium channel
- open and inactivate rapidly
rate of potassium channel
- open and close slowly
what is the result of slow closure of potassium channels?
- the hyper polarization phase
repolarization of the membrane potential occurs due to
- inactivation of voltage gated Na+ channels
- opening of voltage gated K+ channels
Na+/K+ ATPase function
- restore the ionic gradients
the movement of what is responsible for the action potential
- movement of only a few ion molecules
does the intracellular or extracellular concentration of an ion really change at the peak of an action potential?
- not really
absolute refractory period is when
- all Na+ channels are open or inactivated
relative refractory period is when
- K+ permeability is elevated and some Na channels are still inactivated
the refractory zone results in
- propagation of action potentials in one direction
myelin is
- concentric wraps of lipid-rich glial cell processes
myelin surrounds
- axons
what myelinate axons in the peripheral nervous system
- Schwann cells
Schwann bikes hurt my penis
what myelinate axons in the central nervous system
- oligodendrocytes
wraps of myelin do what
- increase resistance of membrane resulting in less leakage of current out of the axon
myelination and speed of conduction of action potential
- myelination increases the speed of conduction of the action potential up to 50 times faster along the length of the axons
saltatory conduction
- wave of depolarization in a myelinated axon jumps for node of Ranvier to the next node of Ranvier
why do unmyelinated axons conduct action potentials more slowly
- due to current leaking out of cell into the ECF
larger diameter axons tend to be
- myelinated
the larger the diameter (in regard to wrapping of myelin)
- the greater the wrapping of myelin
small diameter axons tend to be
- thinly myelinated
- unmyelinated
which are the slowest conducting axons
- small diameter, unmyelinated axons
what is the initiation site for action potentials
why
- axon hillock
- voltage gated Na+ highly concentrated here
where are voltage gated Na+ channels also highly concentrated?
- nodes of Ranvier
