action potential and LA Flashcards
resting membrane potential
-70mV
ICF or ECF more negative?
ICF
sodium potassium poump
3 sodium out
2 potassium in
1 atp
Resting membrane potential is mainly driven by what
K+ diffusing out through K+ channels
resting membrane is very permeable to K+
what does sodium potassium pump do
it also maintians the resting membrane potential at -70
electrogenic
means generates a charge.
Na-K pump generates a charge
upstroke caused by
sodium diffusing in
downstroke
cause by potassium diffusing out
ion channel gates are controlled by?
ligands
voltage
3 states of sodium channels
open, resting, inactivated
m gate vs h gate when the channels are open, closed and in refractory
close -> m gate close h gate open
open -> both open
refractory -> m gate open h gate close
when does sodium channel open?
when it reaches threshold of -55
when does h gate close?
when membrane potential reaches +35 ie the peak
no more sodium can pass
when does potassium channel gate open
opens at the peak ie +35mV
what is the purpose of the refractory period
- ensure AP is in one direction
- limits maximum firing frequency
- prevents summation of AP
what is the def of refractory period
period of inexcitability due to the inactivation of voltage gated sodium channels. the h gate are shut
h gate = inactivation gate
speed of AP propagation increases or decreases with increased diameter?
increases ie large is faster
myelin laid down by what in PNS and CNS
PNS - schwann
CNS- oligodendrocytes
nodes of ranvier
myelin sheath is interrupted at nodes of ranvier
it is here that the axon membrane is exposed to the ECF
so ions can flow between the ICF and ECF, the AP jumps from node to node
endoneurium
perineurium
epineurium
layers of the peripheral nerve
mental nerve vs canine nerve axon diameter
mental nerve => larger
canine => smaller diameter
in tooth pulp are there more unmyelinated or myelinated
unmyelinated
A-beta
A-delta
C
what are the function of each type of nerve fibres
A beta - mechano
Adelta - mechano, thermo, chemo ie taste, nociception
C - nociception, mechano, thermo
A and c are unmyelinated or myelinated?
A - myelinated
C - unmyelinated
what channels do LA block
sodium voltage gated channels
