Lecture 2 Flashcards

1
Q

What is the soma of a neuron?

A

-Cell body (provide metabolic support for neuron)

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2
Q

What are myelinated neurons known as?

A

-Schwann cells

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3
Q

What are the spaces between Schwann cells known as?

A

-Nodes of Ranvier

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4
Q

How many successive nodes have to be blocked to have anesthesia?

A

-3

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5
Q

T/F If only one node is blocked there is enough current to activate the following node

A

True

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6
Q

When delivering anesthetic what order of sensations disappear?

A
  • Pain
  • cold
  • warm
  • touch
  • deep pressure
  • motor (first to reappear)
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7
Q

What two fibers are involved with pain?

A
  • Delta

- dGammaC

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8
Q

What is the nerve membrane composed of?

A

-Phospholipid bilayer

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9
Q

What are the two types of gradients involved with neurons?

A
  • Concentration gradient

- Electrochemical gradient

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10
Q

What is the Resting membrane potential?

A
  • -70 mV
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11
Q

Is the inside or outside portion of the cell negatively charged?

A

-Inside

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12
Q

What occurs in the initial phase of slow depolarization?

A

-Membrane becomes more permeable to Na+ ions mediated by gated ion channels (allows for massive influx of Na+ ions)

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13
Q

What does the rapid influx of Na+ ions change the membrane potential to?

A
  • -55mV (firing threshold)
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14
Q

What does giving local anesthetic do to the firing threshold?

A

-Makes it larger (So instead of going from -70 to -55 it would have to go much further)

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15
Q

What occurs during repolarization?

A

Cell becomes impermeable to Na+ ions and increased permeability to K+ ions

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16
Q

Do the K+ ions get pumped into or out of the cell during repolarization?

A

-Gets pumped from the inside to the outside

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17
Q

What is the magnitude of difference in negative electrical potential needed to initiate an action potential known as?

A

-Firing threshold

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18
Q

What is the firing threshold value?

A

15 mV

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19
Q

What is the first sensation do disappear?

20
Q

Where do local anesthetics work?

A

-Interfere with excitation process (membrane potential, threshold potential, depolarization)

21
Q

What does the membrane expansion theory state?

A

-The membrane shape is changed making it impermeable to ions

22
Q

What is the specific receptor theory?

A

-The local anesthetic blocks passage at specific receptors

23
Q

The sodium channel densities are higher in myelinated or unmyelinated nerves?

A

-Myelinated nerves (20,000 micrometer more)

24
Q

What is the primary action of local anesthetics?

A

-Produce a decrease in Na+ permeability

25
What ions bind to the Na+ channels to open the Na+ channels?
-Ca2+
26
T/F K+, Ca2+, and Cl- remain unaffected by local anesthetics.
True
27
What are essential qualities of a good local anesthetic?
- Non-irritating - Limited damage - Low toxicity - Effective - Short onset - Long duration of action
28
Who is affected by toxicity of local anesthetics most?
-Pediatric patients (lower volume of blood)
29
What are two local anesthetic classifications?
- Amino esters | - Amino amides
30
What type of local anesthetic class is readily hydrolyzed in aqueous solutions?
-Amino esters
31
What type of local anesthetic class is resistant to hydrolysis?
-Amino amides
32
What are the three parts of local anesthetics?
- Lipophilic part - Intermediate chain - Hydrophilic part
33
What are local anesthetics known as in terms of a material?
-Amphipathic materials
34
What is the pKa range of local anesthetics?
-7.5-10
35
Are anesthetics combined with acids?
-Yes (anesthetics are weakly basic)
36
What are the two forms that local anesthetics exist in a solution
- Cation | - Base
37
Does the cation or base travel through the nerve sheath into the intracellular environment?
-Base
38
Once the base enters the intracellular environment what occurs?
-It converts back to the cation stage
39
Do the majority of molecules exist in the cationic or base form for local anesthetics?
-Cationic
40
If a tissue is inflamed what percent of cationic cells of local anesthetics exist?
-99%
41
What is the normal tissue pH?
7.4
42
T/F Benzocaine is readily ionizable
False | -It is not readily ionizable
43
Mucous membrane have what type of buffering capacity?
-Poor
44
T/F Benzocaine is a great topical anesthetic
True
45
Is benzocaine affected by pH?
-No
46
What is the pH of an inflamed area?
5-6
47
The primary action of local anesthetics in producing a conduction block is to decrease the permeability of the ion channel to what ion?
-Na+