The action potential Flashcards
what are muscle spindles
stretch receptors of skeletal muscle
what happens when stretch the mechanoreceptors
opening of Na channels causing receptor potential
what type of potential are receptor potentials
graded - good for strength coding
what happens to receptor potentials over space
decremental - decrease
what does action potential begin
spike initiation zone
how is info coded in action potential
frequency and pattern of AP
5 phases of an AP
- resting
- rising
- overshoot
- falling (repolarizing)
- hyperpolarization
what is AP threshold
minimum voltage that must be reached to initiate - 55mV
what happens with more depolarization
more frequent AP
what limits AP frequency
refractory period (absolute or relative)
what opens with AP
Na and K channels
which channel opens faster
Na, and K sustains over depolarization
what are 3 states of Na channel
- resting
- activated
- inactivated
what reverses inactivation of Na channel
regaining -70
what happens during threshold phase
inward Na> outward L
what happens during rising phase
rapid opening of Na channels
what happen in overshoot
Na inactivation and delayed opening of VG K channels
what happens in falling phase
Na inactivation and K
what happens in hyperpolarization
residuale VG K and IL
what happens in absolute refractory period
Na channel inactivation prevents AP generation
what is direction of Na channel propagation of channel
orthodromic
what determines speed of conduction
length of membrane
what happens with larger diameter axon
less axial resisitance- faster conduction
what forms myelin in PNS and CNS
PNS - schwann cells
CNS - oligodendricites
what are interuptions in myelin
nodes of ranvier
what is conduction that jumps along nodes
saltatoy conduction
what are diseases that demylenate PNS and CNS
PNS - guillain-barre
CNS- MS
how does local anasthetic work
blocks Na channels of pain fibers so can’t give signal
