Neurophysiology neuron Structure



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Lecture 2

NEUROPHYSIOLOGY
Neuron Structure

Sensory Motor

Axon Structure
Membrane Structure

Impulse Conduction

Resting State

Membrane permeability

Ion concentrations

Na+ pump


Excitation

Depolarization

Firing threshold

Repolarization

Absolute refractory period

Relative refractory period

Impulse Spread/Propagation

Unmyelinated


Myelinated

Saltatory conduction


Mode & Site of Action of Local Anesthetics

Na+ channel
Nodes of Ranvier

Anesthetic Molecules

Structure

Ester
Amide


Properties

Weak base

Solubility

Dissociation/Action

Kinetics

Concentration gradient/diffusion

Barriers to diffusion
Properties

lipid solubility

protein binding ability

vasodilation


PHARMACOLOGY OF LOCAL ANESTHETICS
Properties

*Vasodilation


Absorption

GI Tract


Topical

Injection


Distribution
Metabolism

Esters
Amides

Excretion
Systemic Action
CNS

1. anticonvulsive

2. excitatory

3. depression

4. convulsive
Cardiovascular System

Heart


Peripheral
Respiratory system
Drug Interactions

CNS depressants

Common metabolic pathways
Malignant Hyperthermia

PHARMACOLOGY OF VASOCONSTRICTORS

Structure

Catechols

Catecholamines

Natural


Epinehrine

Norepinephrine

Dopamine

Synthetic

Isoproterenol

Levonordefrin



Pharmacology of specific agents

1. Epinephrine

Systemic action

Cardiovascular system

Heart

Peripheral vasculature*



CNS

Respiratory

Uptake

Adrenergic nn.



Bloodstream

Dosage


Healthy = 0.2 mg. per appointment

Cl III or IV = 0.04 mg. per appointment


2. Levonordefrin

Systemic action

Cardiovascular system

Heart


Peripheral vasculature

CNS


Respiratory

Uptake


Dosage: All patients = 1.0 mg. per appointment
Medical Status/Contraindications

1. More Significant CV disease

Hypertension

Post MI


Angina

dysrhythmia

2. Non-cardiovascular diseases

Uncontrolled Hyperthyroid

Uncontrolled Diabetes

Bisulfite Allergy

3. Patient taking the following medications

MAO inhibitors

Tricyclic antidepressants
PATIENT PREPARATION

1. Health history

Allergies

Excessive bleeding

CV disease

Heart failure

Angina pectoris

High BP


Valvular disease

Anemia


Methemoglobinemia

Kidney disease

Thyroid disease

Infectious diseases/decreased liver function

Malignant Hyperthermia

Atypical plasma cholinesterase

Pregnancy

2. Dialogue

Clarify health history

Identify anxious patient


Armamentarium (these three items must always be present/available when administering local anesthesia):

Emergency Drugs

1. Oxygen (positive pressure / 45 min)

2. Epinephrine (pre-loaded syringe, 0.3 ml. (adult) epi 1:1,000)

Emergency Equipment

3. Telephone / Activate EMS (911)
INJECTION TECHNIQUE
Infection control

Needle


sharp, sterile

gauge


Load cartridge

Free-flow

Harpoon engaged

Warm?


Position patient

Dry tissue

Apply topical antiseptic

Apply topical anesthetic

Communicate with patient

Firm hand rest

Make tissue taut

Keep syringe out of sight of patient

Watch and communicate with patient

Advance toward target

Deposit solution before contact with periosteum

Aspirate


Deposit solution SLOWLY

Withdraw needle

Re-cap needle

OBSERVE PATIENT!

Record in chart
Next Week’s Injections

∙ periosteal infiltrations (middle superior alveolar n. infiltration, anterior superior alveolar n. infiltration)

∙ used for single-tooth anesthesia in maxilla; not commonly used in quadrant dentistry (dental hygiene)

region anesthetized:

needle length:

needle gauge:



volume of anesthetic:

depth of penetration:


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