neurophysiology Flashcards
what generates action potencials?
neruons
when do action potencials occur?
when ions flow down electrochemical gradients
what do electrochemical gradients result in?
membrane potencial
what is a membrane potencial
charge difference across cell membrane
measured in volts
voltage represents potencial energy resulting from seperation of oppositely charged particles
what is resting membrane potencial?
70mv
what does polarized mean?
neurons at rest are relative more negative inside then than outside (cells are polarized)
what are the 2 main factors for resting potencial?
na and k exchange pump moves 3na in for 2 k out
leakage of ions varies
what are the different types of ion channels?
leak channels- always open allow passive diffusion of ions
gated channels- open or close in responce to different stimulii
i. ligand-open or close when bind to specific molecules
i. mechanically gated- open or close in responce to membrane distortion
i. voltage gated- open or close in responce to changes in membrane potencial particular voltage
what is an action potencial?
reversal in membrane potencial propagated along the length of the excitable cell neruron or muscle cells
describe action potencial?
stimulas opens voltage gated na plus channels
action potencial propagated along axon of neuron as more voltage gated channels open
resting potencial is restored when na gates close and voltage gated k open
what is resting potencial?
=-70mv
inside of cell is negative relative to inside of cell (polarized)
what is depolarization?
to 30mv
stimulas causes depolarization and volatage gated na channels open = na enflux= more na gates open= action potencial propgated as icf becomes more negative
what is repolarization?
at +30mv na channels close and voltage gated k channels open icf becomes more negative
what is hyperpolarization?
k+ efflux continues and icf becomes even more negative = k gates close at 90mv
why do the na/k. channels keep working
keeps working to restore ion channels