Week 1 Lecture Flashcards
What is an Axolemma?
Cell membrane of an axon.
What is an Axon?
An extension of a centrally located neuron, is the functional unit of peripheral nerves.
What is axoplasma?
Intracellular contents of the axon.
What are the MAJOR components of an axon?
Axoplasm and axolemma.
What are Schwann cells?
Surround, support, and insulate each axon.
What are nodes of Ranvier?
Small segments of nerve that do not contain myelin.
Have limited diffusion barriers for drugs to penetrate.
Therefore - may be primary site for LA’s to exert action.
What are fasciculi?
bundles of axons.
What is saltatory conduction?
This phenomenon significantly facilitates conduction speed along the axon, through large numbers of sodium channels which can generate an intense action potential to jump from node to node.
(it is the movement of an ation potential along the axon from one node of Ranvier to the next node. This increases the conduction velocity without needing to increase the diameter of an axon)
What is the endonerium?
collagenous tissue which surrounds and imbeds axons within the fasciculi (innermost layer of nerve fiber).
What is the perineurium?
Binds fascicles together (middle layer).
What is the epineurium?
Connective tissue that SURROUNDS the perineurium and holds the fascicles together. (outer-most layer) ex: if you inadvertently inject LA directly into this layer, you’ll have prolonged “block” for 3 to 6 months.
What 3 connected layers must LA’s diffuse through to exert pharmacologic action?
- Epineurium
- Perineurium
- Endoneurium
What determines the LA as an ester or amide?
The intermediate chain
What functional state of the sodium channel does an LA exert its action?
Inactive state
Lipid solubility directly correlates to what?
LA Potency
Protein binding directly correlates to what?
LA duration
What is the resting membrane potential?
The voltage difference across the neuronal membrane (-70 to -90 mV)
What is the function of Epi in administration with an LA?
Decreases total required LA dose, decreases uptake, increases duration of action, minimizes bleeding, serves as a MARKER for intravascular injection.
How can you tell difference between an ester and amides?
Two ii’s (and intermediate chain of course)
Which is more cardiotoxic, bupivacaine or ropivacaine?
Bupivacaine