exam 1 Flashcards
what type of gating is LA for the sodium channel
voltage-gated
normally, sodium ________ a cell, the cell becomes more _____________, and _________________ occurs
sodium enters
cell positive
depolarization occurs
LAs block this! They block impulse propagation!
ligand gated involves a ___________ messenger (neurotransmitter) such as ____
second messenger
Ach
LAs are _____-dependent
dose
larger amount of LA blocks a respectively larger number of channels
true or false
nerve fibers can be sensory, motor, or both
true
how are nerve fibers blocked? in order of:
size
myelination variables
what is blocked FIRST, small or large nerve fibers
small fibers (B or C)
what is blocked FIRST, myelinated or unmyelinated
unmyelinated
what type of fibers do LAs work fastest
B fibers
LAs have a _____________/____________ threshold
functional/minimal
true or false
for LAs, until a minimum dose is met, there will be NO effect
true
true or false
LAs are:
concentration-dependent
dose-dependent
volume-dependent
in order to have an effect
true
AFFERENT neurons are also known as
somatosensory
EFFERENT neurons are also known as
motor
what types of nerves are afferent, efferent, and autonomic
SOMATIC portion of the PNS
what do autonomic neurons do
sensory
motor
autonomic functions: signal brain and spinal cord to control visceral elements (hemodynamics, digestion)
spinal nerves that travel to the thoracic and abdominal compartments
intercostal nerves
outside the spinal cord, spinal nerves =
peripheral nerves
what is the functional unit of the nerve
(individual fiber of nerve)
axon
what type of cells surround the axon
schwann (in layers)
myelin sheaths surround the _______
axon
interspersed among the axon at spaces that are NOT myelinated
nodes of ranvier
where is a primary site for LAs action
nodes of ranvier
“Axon intervals”: voltage gated sodium channels that propagate the nerve conduction
nodes of ranvier
true or false, smallest to largest:
fiber/axon < fascicles (bundles of axons) < fibers (afferent/efferent) < peripheral nerve
true
resting membrane nerve potential
-60 to -90 mV
3 states of sodium channel
1) activated/open
2) inactivated/closed
3) resting/closed
where can LAs NOT act
resting/closed
state of sodium channel also known as “refractory period”
inactivated/closed
what are the largest and fastest fibers
A (especially A alpha)
order of ease of blockade (which occur first, then last)
B fibers, C fibers, then A delta, then A alpha
Recovery or “Wearing Off” of Blockade
A-alpha, then A-delta, then C fibers, then B fibers
sensory/afferent = ______lateral aspect of the cord
dorso
(from the body)
motor/efferent = _______lateral aspect of the cord
ventro
(to the body)
These 2 roots converge to form a spinal nerve before dividing into dorsal and ventral rami which innervate anterior and posterior structures
dorsal root
ventral root
subarachnoid/spinal space
_________ dose
smaller
epidural space
_________ dose
larger
how many pairs of spinal nerves
31 pairs
how many bones
33
cervical NERVES
8*
cervical nerves lie ______ the named vertebral body
EXCEPT for ____, which is _________
ABOVE
(except for the 8th, which is below the vertebral body)
cervical VERTEBRAE
7
thoracic NERVES
12
thoracic VERTEBRAE
12
lumbar VERTEBRAE
5
lumbar NERVES
5
sacral VERTEBRAE
5
sacral NERVES
5
coccygeal NERVE
1
coccygeal VERTEBRAE
4*
cervical spinous processes are pointed _________
caudad (toward the feet)
lumbar spinous processes are pointed _________
straight
landmark:
cricoid cartilage
C6
landmark:
most prominent cervical level called “vertebral prominens”
C7
landmark:
superior angle of the scapula and sternal notch
T2
landmark:
plane of Ludwig; carina; angle of Louis
T4
landmark:
inferior angle of the scapulae
T7
landmark:
xiphoid process
T9
landmark:
umbilicus
T10
landmark:
superior iliac crest
L4
what goes farther, sensation or motor?
sensation (dermatomes)
true or false
there is OVERLAP in nerve function
true
plexus:
cervical
C1-C4
plexus:
brachial
C5-T1
plexus:
lumbar
T12-L4
plexus:
sacral
L4-S4
the brachial plexus is located between the __________ and ________ scalene muscles
anterior
middle
Triceps
Supination
Extension of wrist
Extension of other fingers
ABduction of thumb
radial
Follows the track of the brachial artery (lying MEDIAL to it)
Pronates
Flexion of wrist + elbow
Flexion of fingers and thumb
ABduction of thumb
mediaN
Formed from C8-T1
Follows the brachial artery following the posterior aspect of the medial epicondyle
Flexion of wrist, ring, and pinky finger
Flexion of thumb
ADduction of fingers + thumb
ulnar
nerve:
Formed from L2-L4
femoral
nerve:
Formed from L4-S3
tibial
nerve:
Formed from L4-S2
common peroneal
nerve:
Formed from tibial + common peroneal
Extension of hip
Flexion of knee
Plantarflexion of ankle
Dorsiflexion of ankle
All movements of the toes
sciatic
why block a plexus, instead of an individual nerve (2)
- In case there is an anomaly
- Convenience (they are very close together)
binds to the lipid side with carbon OXYGEN
ester
Metabolism: plasma/pseudocholinesterases
Caution with: pseudo cholinesterase deficiency; risk of toxicity due to SLOWER metabolism!
ester
Less stable; shorter ½ life; shorter acting
More easily hydrolyzed/broken apart
ester
Allergies are MORE likely
- Metabolites para-amino benzoic acid (PABA); causes reaction
ester
binds to the lipid side with carbon NITROGEN + HYDROGEN
amide
Metabolism: P450 enzymes (liver)
Caution with: liver disease, protein binding issue, enzyme inducing issue!
amide
More stable; longer ½ life; longer acting
Less likely to be hydrolyzed/broken apart
amide
Some allergies can still occur, rarer
* Due to preservatives such as methylparaben in the LA
amide
most common LAs for allergies:
amide
prilocaine
most common LAs for allergies:
ester
procaine
what is the longest acting ester
tetracaine
_________ are more lipophilic and protein bound of the LAs
longer acting
amides
lipophilic portion (ring)
aromatic ring
linker region (classifies LA)
ester or amide
lipophilic region of LA
hydrocarbon chain
ionizable/hydrophilic region of the LA
tertiary amine
when does metabolism of LAs occur
during “uptake”
once the non-intravascular injected LA gets into circulation/plasma/bloodstream
what is the exception, the only one that does NOT get metabolized by pseudocholinesterase for esters
cocaine (metabolized in the liver)
An LA can have a long clinical effect until it gets into the bloodstream
DECREASES toxicity!
slow uptake
true or false
we want to SLOW the UPTAKE process
true
example: epi
where are plasma/pseudo cholinesterases found
OUTSIDE the NMJ
(in the plasma)
what is Ach metabolized by
acetylcholinesterase drugs (inside the NMJ)
what is the best LA group for true allergic patients
preservative-free amide LA
what 2 LAs are common culprits of methemoglobinemia
benzocaine (hurricane spray)
prilocaine
signs of methemoglobinemia (3)
tachypnea
low PO2 “blue blood”
LEFT shift (inability of Hgb to carry oxygen)
presents like a PE
treatment for methemoglobinemia
methylene blue (1-2 mg/kg IV)
the pH at which ½ of the drug is unionized and ionized
pKa
If a pH solution (patient) is ________ than the pKa of the drug, then the LA becomes more ionized/hydrophilic, and is LESS able to enter the nerve and have its effect
LOWER
with infections, the LA onset is _________ and _______ dense
slower and less dense
another term for lipid-solubility in LAs
alkalization
what 3 things are associated with lipid philicity
binds better to tissue
longer duration
higher potency
_________________ is what allows sodium channel to close
hydrophilicity
When a drug has a HIGH pKA, it becomes more _____________ to enter the nerve for action
high pKa= more DIFFICULT
a HIGH pKa = more ___________/____________
ionized/hydrophilic
this can be exaggerated when pH is lower or with additives that make the pH lower
LAs enter the nerve, ______________________________, ionized portion binds
equilibration of non-ionized and ionized portion = pKa equal
3 factors of duration/longevity of action of LAs
1) starting dose
2) tissue distribution (lipid solubility)
3) drug metabolism = delay of uptake
