neuro physiology of la ppt
TRANSCRIPT
NEUROPHYSIOLOGY OF NEUROPHYSIOLOGY OF LOCAL ANESTHESIALOCAL ANESTHESIA
DR V.RAMKUMARDR V.RAMKUMARCONSULTANT DENTAL & CONSULTANT DENTAL &
FACIOMAXILLARY SURGEONFACIOMAXILLARY SURGEONREG.NO :4118-TAMILNADU REG.NO :4118-TAMILNADU
INDIA(ASIA)INDIA(ASIA)
LOCAL ANAESTHESIALOCAL ANAESTHESIA
It is defined as loss of sensation in a It is defined as loss of sensation in a cirumscribed area of the cirumscribed area of the bodycaused by depression of bodycaused by depression of excitation ina nerve endingsor an excitation ina nerve endingsor an inhibition of conduction process in inhibition of conduction process in peripheral nervesperipheral nerves
METHODS OF INDUCING LAMETHODS OF INDUCING LA
Mechanical traumaMechanical traumaLow temperatureLow temperatureChemical irritantsChemical irritantsNeurolytic agents such as alcohol Neurolytic agents such as alcohol
&phenol&phenolChemical agents such as local Chemical agents such as local
anestheticsanesthetics
WHAT ARE THE PROPERTIES OF WHAT ARE THE PROPERTIES OF LALA
Non irritatingNon irritatingLess systemic toxicityLess systemic toxicityTime of onset to be shortTime of onset to be short Increaseduration of actionIncreaseduration of actionCompletely reversibleCompletely reversibleNon allergic Non allergic To be stableTo be stable
The messages in the form of electric The messages in the form of electric action porentials are called impulses.action porentials are called impulses.
Resting membrane potential( -70 Resting membrane potential( -70 mv) the interior of the nerve is mv) the interior of the nerve is negative relative to the exterior.negative relative to the exterior.
Depolarization- excitation of nerve Depolarization- excitation of nerve segment increase permiability of na+ segment increase permiability of na+ ions into cell membrane.-50 to-60mvions into cell membrane.-50 to-60mv
Repolarization- inactivating the Repolarization- inactivating the increase in permiability of na+ ions , increase in permiability of na+ ions , there may be incerase in permiability there may be incerase in permiability of k+ ionsof k+ ions
Impulse spread- slow in un Impulse spread- slow in un myelinated nerve fibres myelinated nerve fibres
Myelinated nerve fibres- increase Myelinated nerve fibres- increase spread due to myelination and spread due to myelination and insulating material , impulse insulating material , impulse conduction occurs by means of leap conduction occurs by means of leap from node to node by process called from node to node by process called saltatory conduction saltatory conduction
Impulse propogation- impulse moves Impulse propogation- impulse moves along the surface of axon by energy along the surface of axon by energy derived from nerve membranederived from nerve membrane
Mode And Site Of Action Of LaMode And Site Of Action Of La
Altering the basic resting potential of Altering the basic resting potential of nerve membranenerve membrane
Altering the treshold potentialAltering the treshold potentialDecreasing the rate of depoalrizationDecreasing the rate of depoalrizationProlong the rate of depolarizationProlong the rate of depolarization
HOW DO THE LA WORKHOW DO THE LA WORKVARIOUS THEORY OF LAVARIOUS THEORY OF LA
Acetyl choline theoryAcetyl choline theoryCalcium displacement theoryCalcium displacement theorySurface charge theorySurface charge theoryMembrane expansion theoryMembrane expansion theorySpecific receptor theorySpecific receptor theory
Acetyl choline theory- it mainly acts Acetyl choline theory- it mainly acts on the neuro transmitteron the neuro transmitter
Calcium displacement theory-Calcium displacement theory-diplacement of calcium ion from cell diplacement of calcium ion from cell membrane ,controlled permiability of membrane ,controlled permiability of sodium ionsodium ion
Surface charge theory- changing the Surface charge theory- changing the electrical potential at th enerve electrical potential at th enerve membrane, binding the nerve membrane, binding the nerve membrane to la moleculesmembrane to la molecules
Membrane expansion theory- la Membrane expansion theory- la binds to the hdrophobic region binds to the hdrophobic region increase in bulk structure by increase in bulk structure by expansion of the membraneexpansion of the membrane
Specific receptor theory- la binding Specific receptor theory- la binding to specific receptor to sodium to specific receptor to sodium channel channel
CLASSIFICATION OF LOCAL CLASSIFICATION OF LOCAL ANESTHETIC SUBSTANCE ANESTHETIC SUBSTANCE
ACCORDING TO THE BIOLOGIC ACCORDING TO THE BIOLOGIC SITE AND MODE OF ACTION SITE AND MODE OF ACTION
definition chemical definition chemical substancesubstance
Class A Receptor on - BiotoxinsClass A Receptor on - Biotoxinsxternal surface of nerve membranexternal surface of nerve membrane classB- Receptor on internal -Quartenary classB- Receptor on internal -Quartenary surface of nerve membrane ammoniunsurface of nerve membrane ammoniun classC-receptor independent - Benzocaine classC-receptor independent - Benzocaine physiochemicalmecahnismphysiochemicalmecahnism classD – combination of receptor - LAclassD – combination of receptor - LA&receptor –independent mechanism&receptor –independent mechanism
HOW DOES LA WORKHOW DOES LA WORK
Displacement of calcium ions from sodium Displacement of calcium ions from sodium channel receptor sitechannel receptor site
Binding of la molecule to the receptor siteBinding of la molecule to the receptor site Blockade of sodium channelBlockade of sodium channel Decrease in sodium conductanceDecrease in sodium conductance Depression of rate of electrical Depression of rate of electrical
depolarizationdepolarization Failure to achieve the threshold potential Failure to achieve the threshold potential
levellevel Lack of development of propagated action Lack of development of propagated action
potential levelpotential level Conduction blockadeConduction blockade
Nerve block produced by local anesthetics is Nerve block produced by local anesthetics is called non depolarizing nerve block because called non depolarizing nerve block because the nerve is unable to relaese energythe nerve is unable to relaese energy
Diffusion- the movement of LA from extra Diffusion- the movement of LA from extra cellular neural deposition site towards the cellular neural deposition site towards the nervenerve
Mantle bundles- fasiculi located near the Mantle bundles- fasiculi located near the surface of the nerve they are the first one surface of the nerve they are the first one reached by LA due to increase concentrationreached by LA due to increase concentration
Core bundles fasiculi- located closer to the Core bundles fasiculi- located closer to the centre of the nerve their action is decreasecentre of the nerve their action is decrease
Blocking process- some of the LA are Blocking process- some of the LA are absorbed by nerve through diffusionabsorbed by nerve through diffusion
Induction time- is defined as the Induction time- is defined as the period from deposition of the period from deposition of the anesthetic solution of complete anesthetic solution of complete conduction blockadeconduction blockade
Vasoactivity- increase in injection of Vasoactivity- increase in injection of LA into the blood vessel causes vaso LA into the blood vessel causes vaso dilatationdilatation
Factors affecting local anesthetic Factors affecting local anesthetic actionaction
Factor Action affected DescriptionFactor Action affected Description Pka onset lower pka Pka onset lower pka
increaseincrease action onsetaction onset Lipid solubility Anesthetic potency increased Lipid solubility Anesthetic potency increased
lipid lipid solubility increased solubility increased
potency potency Protein binding Duration increase Protein binding Duration increase
protein protein binding binding increase increase duration of action duration of action
Factor Action affected Description Factor Action affected Description Non nervous onset increased Non nervous onset increased
diffusibility diffusibility
tissue diffusibility tissue diffusibility
Vaso dilator activity anesthetic potency Greater Vaso dilator activity anesthetic potency Greater
Duration vasodilator Duration vasodilator activityactivity