Action Potential And Loca Anaesthesics Flashcards
What is conductance
movement of ions across the membrane
Directly proportional to the number of open channels and so the permeability
When there are more channels open there would be more conductance
What is saltatory conduction
Depolarisation and propagation of action potential would happen at one of the nodes of ranvier.
Since the nerve would be myelinated, the action potential would move to the next node where there would be depolarisation
This would allow the impulse to travel further and faster
What is the difference between the glial cells and the Schwann cells
Glial cells would be in the CNS
Schwann cells would be in the peripheral nervous system
What is the absolute refractory period and what would cause it
Period between two action potentials where another CANNOT be created
As all the NA+ channels would be inactivated
What is the relative refractory period and why does it happen
When there would need to be more depolarisation for there to be another action potential
There would be some inactivated NA+ channels but a lot of open K+ channels
Would need more depolarisation to override this
What factors would increase the conductance velocity
Myelinated neurones
Large diameter of neurones
What are the 4 steps of local anaesthetics
Delay of threshold
Reduced level of depolarisation
Reduced rate of action potential
Failure to create action potential
What is tetrodotoxin
Toxin that would be present in Japanese puffer fish
Blocks the NA+ channels
What does scorpion poison do
Opens the NA+ channels and keeps them open
Have the constant stimulation and therefore constant pain
How do local anaesthetics work
Diffuse through the membrane
Bind to sodium channels on the inside
Weak bases so would dissociate
Ion would bind to the channel
Would want to bind when the NA+ channel is inactive
What does lidocaine treat
Cardiac Arrhythmia
What does tocainide treat
Cardiac arrhythmias and neuropathical pain
What does phenytoin treat
Epileptic convulsions
How would unwanted side effects of local anaesthetics be caused and where could they act.
From too high doses
Move in the blood and act in blood vessels causing dilation and contraction
Act in the brain causing stimulation or suppression
Could also act in the heart causing cardiac arrhythmias
Name some ways to administer local anaesthetics
Intradermal
surface (spray, nose, throat)
Epidural
Nerve blockage (dentistry)
