Neurophysiology & Pharmacology of Dental LA

What is the SENSORY NEURON that brings signals TOWARD the brain and spinal cord?

Afferent

What is the MOTOR NEURON that brings signals AWAY from the brain and spinal cord to muscles and glands?

Efferent

What Nerve carries information from the periphery of the body to the brain

Aferent - Sensory

What is the Insulating and protective lipid-rich layer around the Axon?

Myelin

This is responsible for producing and maintaining the myelin sheath.

(Facilitates the healing process after injury)

Schwann cells

The gap(s) between adjoining Schwann cells and myelin spirals.

Nodes of Ranvier

What ion passes through the nerve membrane easily?

RN (neutral base)

What is NOT true about myelinated nerves?

It slows the transmission of impulses.

What are the steps of electrophysiology of nerve conduction?

1.) Resting state/potential

2.)Membrane Excitation (stimulus)

3.) Nerve Potential Generation

4.) The Wave Effect

5.) Repolarization (reset)

Acts like a battery with different charges inside and outside.

Resting state/potential

What part of the nerve has more (Na+) and (Cl-) and has a positive charge?

Outside or External

What part of the nerve has more (K+) and a negative charge?

Inside or Internal

Pressure, temperature, or chemicals that trigger the nerve and change the inside from negative to positive (depolarization).

Membrane excitation

What is it when sodium rushes through the sodium and changes from negative to positive?

Action potential generation

This is how the messages moves along the nerve ( domino effect).

The wave effect

Returns to resting state, sodium channels close automatically, potassium channels open, and the membrane returns to negative charge.

Repolarization ( reset)

How does dental local anesthetic work?

Blocking sodium channels

Immediate after stimulus has initiated action potential unable for a time to respond to another stimulus.

Absolute Refractory Period

When a new impulse may be generated by A stronger than normal stimulus.

Relative Refractory Period

Fast conduction, jumps between nodes, sharp, precise pain, cold sensitivity, first to be blocked by Local Anes. Sharp tooth pain.

A fibers - myelinated

Facts about myelinated nerves.

Impulses are carries through the Nodes of Ranvier

Insulation along the nerve axon

Schwann cells are responsible for creating myelin sheaths

Slow conduction, most common, dull burning pain, tension and pressure, thermal pain (hot or cold). Lingering toothache.

C - fibers - unmyelinated

What fibers are found in the dental pulp?

Both A & C fibers

The sequence of successful impulse generation

Resting state, stimulation, slow depolarization, firing threshold, rapid depolarization, repolarization, recovery.

What nerves doe the Local Anes effect?

Both Sensory and motor nerves

What nerve is affected first Motor (large) or Sensory (small)?

sensory (small)

What two anesthetic agents can be use topically and subcutaneously

Lidocaine and prilocaine

What is true about nerve membranes (neurolemmas)?

Hydrophilic ends of the membrane are facing out

Lipophilic ends of the membrane are facing in

What is the order of the blockade of Local Anes.

1.) pain sensation fibers

2.) temperature sensation

3.) touch sensation

4.) pressure sensation

The main reason anesthesia fails to occur near an abscessed tooth?

Infection causes a decrease n the tissue pH.

What the factors affect Local Anes success?

pH factor of tissue

Blood flow in the area

Accuracy of placement

type of nerve being blocked

concentration of drug

What element needs to be blocked for there to be no nerve signal?

Sodium

The ACTIONS of a drug on the body

Pharmacodynamics

The manner in which the body MANAGES the drug (absorption, distribution, metabolism, elimination)

Pharmacokinetics

The rate of which a drug is removed from the systematic circulation by the kidneys.

Half - life

How much of a drug would be life in the system on the 3rd half - life?

25%

What is elimination half-life refers to what?

The time it takes for half of the drug to be out of the circulation

What anesthetic is primarily metabolized in the blood (cholinesterase)?

Articaine

Local Anesthetics works by penetrating the nerve to inhibit?

Na+ influx

What component of Local Anes renders the molecule water-soluble?

Hydrophilic amino group

Uncharged form of (RN), neutral pH base, can NOT attach to the receptor in channel.

Lipophilic

Charged from (RNH+) cation, low pH, attaches to the receptor in NA+ channel

Hydrophilic

What are examples of Local Anes Amides?

Lidocaine

Bupivacaine

Mepivacaine

Prilocaine

Articaine

Where does the metabolism of the amide anesthetics occur?

The Liver

What are examples of Local Anes Esters?

Cocaine

Procaine

Benzocaine

Tetracaine

chloroprocaine

The metabolism of the anesthetic esters occurs by?

an enzyme cholinesterase

The drug that constricts peripheral blood vessels

Vasoconstrictors

What may be a sign of epinephrine overdose?

Resemble CNS depression which include: drowsiness, slurred speech, confusion, dizziness, poor coordination, slowed breathing and heart rate.

What is Phase I of CNS?

Excitation - signs of fear and anxiety.

What is Phase II of CNS?

Depression - tonic clonic seizures, coma and respiratory arrest.

What is Phase I in CVS?

Heart rate and blood pressure increase.

What is Phase II in CVS

Vasodilation continues leading to a fall in BP, reduced cardiac output, and respiratory arrest.

Facts about RNH+ of the local anesthetic ion?

Blocks the nerve impulse

the working form of the drug

blocks the calcium channel

What is true about the cation RNH+ charged form?

it has low pH