1.2 Neurophysiology of the Trigeminal Nerve

Local anesthesia

A loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves. It’s designed to induce a transient and completely reversible state of anesthesia.

Systemic toxicity; rapid

When choosing a local anesthetic for numbing, a desirable formulation will have low _______ _________, will have a ________ onset, and should be non-irritating to the surrounding tissue

Nodes of ranvier

The gaps between the Schwann cell sheath that surrounds the axon; results in faster speed of impulse conduction

Action potential

A stimulus strong enough to cause a transient membrane depolarization in a nerve

Increased

When an action potential is initiated, it results in an ________ permeability of the neural membrane that allows the transfer of chemicals into and out of the cell and creates an electrical stimulation

Absolute refractory period

The event of nerve conduction sequencing in which the cell is depolarized, all the sodium channels are open, and potassium begins to leak out. The nerve cannot respond to additional stimuli.

Relative refractory period

During this event in nerve stimulation, the neuron can respond to stimuli, but a stronger stimulus is required.

Sodium

During repolarization, what ion is actively transported out of the cell?

specific receptor theory

This theory proposes that LA bind to specific receptors on the sodium channel and keep sodium out, therefore interrupting neural conduction

esters and amides

What are the two classifications of LA molecules?

amides

Which LA molecule type typically has two “i”s in its name?

uncharged base, intermediate chain, positively charged cations

What are the 3 parts of anesthetics?

intermediate chain

What part of the LA determines if it is an ester or an amide?

salts

LAs are dispensed as ______ and dissolved into water or saline to make them both soluble and stable

True

T/F: RNH⁺ has to dissociate into RN and H⁺ in order to diffuse through the nerve sheath

True

T/F: Once inside the cell, RN must revert back to RNH⁺ because it can’t exist in RN form. Once it returns to RNH⁺ it can bind to the sodium channel receptor sites and provide a conduction blockade.

without; with

LAs ______ vasoconstrictor have a pH value between 5.5 and 7. LAs _____ vasoconstrictor have a pH value around 3.3.

True

T/F: The lower pH of LA containing vasoconstrictor prolongs the drugs effectiveness

lower

______ pK_a values result in a more rapid onset of LA

False

T/F: LAs with high vasodilating ability that don’t include vasoconstrictors last longer than those with.