Pain Physiology Flashcards
Main difference of local anesthesia from general anesthesia
LA = loss of sensation without loss of consciousness
Methods to induce LA (6)
mechanical trauma
low temperature
anoxia (loss of oxygen)
chemical irritant
neurolytic agents (damage nerve)
chemical agents
Desirable properties of LA (6)
Non-irritating
Reversible
Low Systemic Toxicity
Effective regardless of mode of delivery
Fast time of onset
Long Duration of action
Explain the dynamite analogy of pain physiology
Nerves work like dynamite, in which the spark is the stimulus travelling through the fuse that is the nerve creating an explosion, which is the impulse/signal to be interpreted as pain. LA then works like water which stops the spark from travelling along the fuse
Phases of nerve conduction
Resting phase
Slow depolarization phase
Rapid depolarization phase
Repolarization phase
Electrophysiology at resting phase
no stimulus, no action potential, no impulse
-70mV
T/F. LA do not work on nerves in resting phase
T
Electrochemistry at resting phase
-70mV
selectively permeable to Na+
freely permeable to K+ and Cl-
Electrophysiology at slow depolarization phase
-50mV to -60mV
introduction of stimulus
Na+ enters
before firing threshold is met
Electrochemistry at slow depolarization phase
stimulus leads to increase in sodium permeability
Electrophysiology at rapid depolarization phase
after firing threshold is met = rapid reversal of polarization
influx of Na+
positive intracellularly (+40mV)
Electrochemistry at rapid depolarization phase
influx of Na+
positive intracellularly (+40mV)
Electrophysiology at repolarization phase
-60mV to -90mV
revert to resting potential
outflux of positive ions
Electrochemistry at repolarization phase
Na+ flows out
-60mV to -90mV
Ways to block nerve conduction (4)
- Alter basic resting potential
- Alter threshold potential
- Decrease rate of depolarization
- Prolong rate of repolarization
