Exam 2 part 1 Flashcards
________________ was the first muscle relaxant used, but was actually used as an anticonvulsant
curare
what is your depolarizing muscle relaxant
succinylcholine
how do you reverse succinylcholine
time
why do we give NMBA
- intubation - protect against vocal cord injury 2. facilitate surgical exposure 3. increase efficacy of mechanical ventilation
T/F: NMBA produce paralysis and anesthesia
false; only produce paralysis
muscle relaxation does not ensure ______________, ___________, or _______________
unconsciousness; amnesia; analgesia
Acetylcholine (Ach) is a _________________ ammonium ester
quarternary
Ach release is dependent on _____________
calcium
T/F: Ach is not recycled or reused so it must be synthesized constantly
TRUE
choline + ____________________ in a reaction controlled by ______________________ –> Ach
AcetylCoA; cholineacetyltransferase
vesicles in motor nerve endings contain _______________________ molecules of Ach
5000 - 10000
Ach is hydrolyzed in < __________ ms by _____________________
15; acetylcholinesterase
acetylcholinesterase breaks Ach into _____________ + ____________
choline + acetic acid
each molecule of acetylcholinesterase degrades _________________ molecules/s of Ach
25,000
________________ re-enters the motor nerve terminal to be resynthesized to Ach
choline
________________ nerves originate in the anterior (ventral) horn of the spinal cord and terminate in skeletal muscle
efferents (motor)
________________ nerves originate in the skeletal muscle and carry signals to the spinal cords posterior (dorsal) horn
afferents (sensory)
suggamadex reverses what NMBA
rocuronium and vecuronium (NDMR)
suggamadex can reverse certain NDMR without relying on inhibition of ______________________
acetylcholinesterase
Ach is released from what nerves?
- somatic motor nerves 2. preganglionic sympathetic nerves 3. preganglionic parasympathetic nerves 4. postganglionic parasympathetic nerves 5. postganglionic sympathetic sweat glands
resting transmembrane potential of the Neuromuscular junction is
- (-)90 mV
what comprises the neuromuscular junction
- motor nerve terminal 2. synaptic cleft 3. motor end plate
what is the basis for normal neuromuscular transmission
flow of ions
______________ would decrease the amount of Ach that is released from the motor nerve terminal (presynaptic membrane)
hypocalcemia
________________ would increase the amount of Ach that is released from the motor nerve terminal (presynaptic membrane)
hypercalcemia
on the motor end plate (neuromuscular jx) what receptor does acetylcholine bind to
nicotinic
for the motor end plate of the muscle cell to depolarize what subunits of the nicotinic receptor have to be occupied? then ______________ flows through the receptor causing further depolarization of the membrane
both alpha subunits; cations (sodium and calcium into cell & potassium out of cell)
describe the process of muscle contraction starting from the Ach binding with both Alpha subunits of the Nicotinic receptor on the motor end plate
- causes depolarization and causes sodium and calcium to flow into cell and potassium out (further depol) - this action potential moves down Ttubule opening VG sodium channels –> SR to release more calcium - calcium binds with troponin allowing actin and myosin to interact –> muscle contraction
after muscle contraction is conducted (actin and myosin interaction) what happens?
- Ach is hydrolyzed by AchE –> decreasing Ach in Synaptic cleft 2. causes ion channels to close –> membrane repolarization 3. calcium is actively resequestered to the SR 4. muscle cell relaxes awaiting another AP
there are _________________ nicotinic receptors on the motor endplate, but for a muscle to contract only need __________________ activated
5 million; 500,000
depolarizing muscle relaxants (succinylcholine) interrupt what part of the cycle of generating a muscle contraction?
after the muscle contracts and Ach is broken down by AchE, it inhibits the ion channels from closing. This inhibits another AP from being able to be generated
what are the 5 subunit proteins of the fetal postjunctional nicotinic receptor
2 alpha, 1 beta, 1 gamma, 1 delta
nicotinic receptor has how many subunits
5
_______________ nicotinic receptor is described as immature and unstable because of the ______________ subunit
fetal; gamma
what are the 5 subunits of the adult nicotinic receptor
2 alpha, 1 beta, 1 delta, 1 epsilon (epsilon replaces the fetal gamma subunit)
in the adult nicotinic receptor, the fetal gamma subunit is replaced by the epsilon subunit, what advantages does this bring?
- mature, stable receptor 2. increases cation conductance 3. shortens the open ion time
which nicotinic receptor can exist outside of the NMJ (fetal or adult)
fetal (gamma subunit)
up-regulation of receptors is a response to _________________, and down regulation of receptors is a response to ________________.
antagonists; agonists
situations/conditions where nicotinic Ach Receptors are upregulated (and show up extrajunctionally)
- SCI 2. ECT therapy 3. CVA 4. thermal injury 5. prolonged immobility 6. prolonged exposure to NMB 7. MS 8. Guillian barre
situations/conditions where nicotinic Ach Receptors are down regulated
- myasthenia gravis 2. organophosphate poisoning 3. anticholinesterase OD
extrajunctional nicotinic receptors have which subunits (gamma or epsilon)
gamma (so are immature fetal like nicotinic receptors)
Burn patients begin to upregulate nicotinic Ach receptors as early as ________________ hours after the burn and last up to ________________months
24-48; 4-6
which NMBA is avoided in situations of upregulated nicotinic Ach Receptors
succinycholine (it will hit the extrajunctional receptors)
what is the function of prejunctional nicotinic receptors
- increase the synthesis and release of Ach (via positive fdbk) 2. prevents the depletion of Ach
T/F: nicotinic receptors are present in the SNS and PNS
TRUE
T/F: muscarinic receptors are present in the SNS and PNS
false; specific to the PNS
MOA of succinylcholine
binds the alpha subunits of the nicotinic receptor keeping the ion channel open, thus keeping the cell depolarized
succinylcholine is broken down by __________________in the _________________
pseudocholinesterase (aka plasmacholinesterase) ; blood
______________________ is a chemical compound of 2 joined Ach molecules
succinylcholine
succinylcholine is a ___________________ ammonium compound, meaning it does not cross the ________________ or the ____________________
quaternary; BBB; placenta
describe the pharmacokinetics of succinylcholine
- low lipid solubility 2. highly ionized 3. water soluble 4. small Vd (quick on/off) 5. highly protein bound
what is the NMBA drug of choice for RSI
succinylcholine
___________________ is a nicotinic Ach receptor Agonist
succinylcholine
___________________ is a NMBA that produces intense paralysis rapidly, but effects decrease before an adequately preoxygenated pt becomes hypoxic (d/t spontaneous breathing returning)
succinylcholine
T/F: succinylcholine depolarizes the nicotinic Ach receptor over and over until degraded
false; it only depolarizes the receptor one time
T/F: succinylcholine is degraded by Acetylcholinesterase
FALSE
succinylcholine is a _________________ block
non-competitive
succinylcholine keeps the cell in a depolarized state, which means what?
- a depolarized post-junctional membrane cannot respond to a subsequent Ach stimulus
- sodium channels remain in an inactive state
typically NMBA are dosed via ____________________, but with obese pts succinylcholine is dosed via ____________________
lean body weight; total body weight
onset of succinylcholine
30-90 seconds
