Action Potentials Flashcards
Why are AP’s imp for dentists
for local anaesthesia and pain etc
what are the diffenret chemical singling of the body
short distance - synapse
long distance - hormones
how fast is the chemical singling in the body
relatively slow
what are the types of electrical signalling in the body
graded potentials
AP’s
what are graded potentials
short distance
vary
fizzle out at nerve endings
what are AP’s
long distance
all or none
fast 120m/s
is the nerve membrane a good insulator
no poor as phospholipids are leaky and in aq enviro
is the cytoplasm good conductor
no poor
what happens to signals in nerves over 2-3mm and what is this due to
decays
due to high resistance and poor insulation
what is used in nerves to help with propagations of signals
AP’s
what is a resting mem pot
Separation of opposite charges across a membrane
what causes a rest mem pot
perm of key ions
corn grad for key ions
gradients maintained by active transporters
do all cells have rest me pot
yes
what are excitable cells
nerve and muscle
what are the extra/intracellular conc and relative perm of Na, K an anion
Na
extra - 150
intra - 15
RP - 1
K
extra - 5
intra - 150
RP - 25-30
anion
extra - 0
intra - 65
RP - 0
roughly explain the Na/K pump
uses ATP
transports 3 Na out
2 K in
helps maintain conc grads
si the mem perm or imperm to K
perm at rest
what is the electrochem gradient for K
chemical - k out
electrical - protein anions cant flow out so k attracted in
what is the nernst value for K equilibrium potential
-90mV
what si the mem at rest like toward Na
much less perm to Na
what si the nernst eon value for Na
+60mV
how si the resting mem potential formed
due to effects of K and Na
ion with > perm drives mem potential
at rest what is the RMP closer to
K equilibrium potential
what is the RMP based on
based upon all ions in goldman eqn
what is the importance of -50mV
threshold for AP all or none
what is depolarisation
going upward more positive cause potential to go up sodium channels open
what happens after depolarisation overshoot
K channels delay open and Na channels inactivate rapid depolarisation
K out
what is hyperpolarsation
below threshold K channels close and N channels reset
what is the hodgkins cycle
threshold depo Na channels open increase na perm Na moves into cell Depo N channel open
how do ‘caine’ anaesthetics affect he hodgkins cycle
hold Na channels reversibly closed
what is AP propagation
local current flow to adjacent area raise pot to threshold voltage gated N channel open poitve feedback porpaget along axon
what si a refractory period
time when cannot reactivate a Na channel
what are th two types of refractory period
absolute and relative
what is an absolute refractory period
Na channels not in rest configuration
an AP can’t occur
what is a relative refractory period
K gates open
mem is hyper polarised
an AP can occur need larger stimulus
what does a refractory period do in terms of directions
means that nerve signals cannot backfire only propagated in one direction
what does the width of an axon do to conduction velocity
increase axon diameter
lower resistance
faster conduction
what does myelination do to conduction velocity
insulates
node ranvier jumps
local current flow node to node
depo jumps
what re the types of nerve fibres
C
A delta
A beta
A alpha
what does a C nerve do
slow burning pain
high resistance coz thin and non myelin
smallest nerve slow velocity
what is a A delt nerve
faster sharp pain
myelin sheath so faster condition and is wider
what is a A beta nerve
wider and myelinated
sensory ones, mechanoreceps
what is a A alpha
biggest nerve
motor to muscles
widest and myelinated
why rent all nerve A alpha
to big to fit in body need small to fit in places or would be huge
what re incoming nerves
afferent from periphery to centre
what are outgoing nerves
efferent from center to periphery
what are the fastest nerves linked to
proprioception - knowing about self form and what body doing
what is good to keep in mind about nerve size with dentistry
affects diff with LA
what are the easiest yes of nerves to block
smallest most difficult widest
what are he first type of nerves to be blocked
pain then touch
