TRACHTE Flashcards
How many efferent fibers come from spinal cord in somatic nervous system?
1
neurotransmitter in somatic nervous system
acetylcholine
receptor in somatic nervous system
nicotinic
What can activate nicotinic receptor
acetylcholine or nicotine
6 steps that activation results in - step 1
Na influx
6 steps that activation results in - step 2
depolarization
6 steps that activation results in - step 3
muscle action potential
6 steps that activation results in - step 4
opening of voltage sensitive calcium channel
6 steps that activation results in - step 5
release of calcium from sarcoplasmic reticulum
6 steps that activation results in - step 6
contraction
efferent nerves from the spinal column virtually always release..
acetylcholine
toxin from krait that blocks neuromuscular nicotinic ion channel
alpha - bungarotoxin or cobra venom
Do somatic nerves have a synapse outside the spinal cord?
No (that’s autonomic nerves)
Nerve activation leads to 9 things….1
acetylcholine release
Nerve activation leads to 9 things….2
nicotinic receptor activation
Nerve activation leads to 9 things….3
sodium influx
Nerve activation leads to 9 things….4
muscle endplate depolarization
Nerve activation leads to 9 things….5
muscle action potential
Nerve activation leads to 9 things….6
calcium influx
Nerve activation leads to 9 things….7
calcium induced calcium release from sarcoplasmic reticulum
Nerve activation leads to 9 things….8
calcium interaction with troponin
Nerve activation leads to 9 things….9
myosin-actin interaction (muscle contraction)
What drugs could prolong acetylcholine actions?
anticholinesterases: neostigmine, pyridostigmine, edrophonium
If something blocks acetylcholine release, what is prevented (2 things)
- muscle depolarization
Something that blocks nicotinic receptors will prevent.. (2 things)
muscle depolarization
drug that prevents AcH release
botulinum toxin
drugs that block nicotinic receptors (useful in surgery)
mivacurium
Something that blocks calcium induced calcium release will block…
contraction! (but not depolarization)
drug that blocks calcium induced calcium release
dantrolene
What is useful for treating myasthenia gravis
anticholinesterases
What do anticholinesterases do?
increase acetylcholine concentrations in the vicinity of the nicotinic receptor (outside the somatic nerve)
charge of acetylcholine
negative (comes from aspartic acid)
what does acetylcholine get broken down to?
acetic acid and choline
2 carbamate drugs
neostigmine
stimulates nicotinic receptors, useful for myasthenia gravis, abdominal distension or atony of detrusor muscle. More often used in the hospital only though.
Neostigmine (quaternary ammonium)
delivery of neostigmine
oral or parenteral
Used in myasthenia gravis or to reverse competive neuromusclar antagonism; can also be used prophylactically to prevent action of nerve gas.
Pyridostigmine
Why is pyridostigmine used more in patients?
It is better absorbed orally.
Why can pyridostigmine be used with nerve gas/
It could occupy some sites of Ach and prevent acetylcholinesterases from binding there
Therapeutic idea in myasthenia gravis
increase Ach concentrations to increase interactions with nicotinic receptors. Nicotinic receptors are depleted in MG so must increase Ach to get interaction w/Nic receptor.
On a response vs acetylcholine concentration plot, what way would it shift if neostigmine was administered?
left shift
Reversilbe anticholinesterase that is administered parenterally and is very SHORT ACTING
Edrophonium
What is edrophonium good for?
diagnosing myasthenia gravis and treating paraoxysmal supraventricular tachycardia
If an increase in strength is seen after administering edrophonium…
myastenic crisis
if a decrease in strength is seen after administering edrophonium…
cholinergic crisis
cholinergic crisis
If there person is getting too much acetycholinesterase, the edrophonium will make them weaker.
unique property of acetylcholine related to activation:
excessive stimulation desensitizes the organ to further stimulation (principle behind cholinergic crisis)
Acetycholinesterase toxicity
Sludge
S
sweating
L
lacrimation
u
urination
D
diarrhea
G
GI distress
E
emesis (vomiting)
What causes SLUDGE
stimulation of organs in body that respond to parasympathetic innervation, lung constriction, pinpoint pupils
Where are neuromuscular blockers used?
surgery
2 types of neuromuscular blockers
competitive and depolarizing
Mechanism of neuromuscular competitive blockers
competitively compete for nicotinic receptor sites
What parts of contraction, etc. are blocked w/neuromuscular competitive blockers?
Na influx (compete for nicotinic sites)
How do depolarizing agents work?
depolarize END PLATE OF MUSCLE - leads to chronic Na influx
How do competitive agents work on muscles..
affect smaller muscles first then larger ones
What can reverse competitive blockers?
acetylcholinesterase (neostigmine, etc)
What is most sensitive to depolarizing agents?
chest and abdomen
What does acetylcholinesterase do to depolarizing agents/
may augment block (increase intensity)
What do you see with depolarizing agents?
twitching before paralysis
What effects occur from neuromuscular blockers (4)
paralyze skeletal muscle
When don’t you want to use neuromuscular blockers
burn patients
Examples of competitive blockers
d-tubocurarine
examples of depolarizing agents
succinylcholine
what can enhance competitive block?
ether
What has slight ability to reverse competitive blockade due to beta 2 receptors on muscle
epinephrine
toxic effects of neuromuscular blockers
apnea
what can cause malignant hyperthermia
halothane
treatment for malignant hyperthermia
dantrolene
what does dantrolene do?
inhibits calcium release from sarcoplasmic reticulum by blocking the Ryanodine receptor
What does dantrolene prevent?
CONTRACTION
Absorption of neuromuscular blockers
intravenously (quaternary ammonium)
How are neuromuscular blockers usually excreted
kidneys
what drug is not excreted by the kidneys
atracurium
uses of neuromuscular blockers
anesthetics
What are resistant to succinylcholine
myasthenics
what potentiates succinylcholine effects
anticholinesterases
What should you check for in patient before giving succinylcholine
butyrylcholinesterase
What does butyrylcholinesterase do?
degrades succinylcholine (gives short duration due to rapid metabolism)
Other side effects of succinylcholine
can produce malignant hyperthermia
when is succinylcholine used
shorter procedures
what does succinylcholine do to the contraction/acetylcholine concentration curve
flat lines (no contraction occurs)
what does tubocarine do to the contraction/acetylcholine concentration curve
shifts curve to the right - decreases contraction of muscle (need higher Ach for contraction to occur)
prevents acetylcholine release by cleaving proteins (SNAP25) necessary for acetylcholine exocytosis
botulinum toxin A (botox)
where is botox injected
region of spastic muscle
how long does botox last
3 months
what can botox treat
spasms of eye
most potent lethal toxin known (8 serotypes, only 3 have antisera)
botulinum toxin
Prevents CONTRACTION and malignant hyperthermia
dantrolene
Potentiate contraction w/antichoinesterases
neostigmine
What drug would BLOCK action potential from occuring
tubocurarine (competitive)