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PHAR 341 - Pharmacology > Neuromuscular Junctions > Flashcards

Neuromuscular Junctions Flashcards

1
Q

Normal function of neuromuscular junctions

A
  • release neurotransmitters into the space
  • have the neurotransmitters activate receptors
  • cause muscle contraction
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2
Q

How Acetylcholine is released at the neuromuscular

A
  1. Choline and AcetylCoA are transfered and bound via Choline Acetyltransferase
  2. Packaged into Vesicles
  3. Vesciles bind to the membrane
  4. Release Acetylcholine (neurotransmitter)
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3
Q

How Acetylcholine is recycled at the neuromuscular junction:

A
  1. Acetylcholinesterase breaks down Acetylcholine into Acetate and Choline
  2. Choline is transfered into the cell via Choline Transporter proteins
  3. it then combines with AcetylCoA
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4
Q

Where and How do Acetylcholinesterase Inhibitors act:

A
  • block the conversion of ACh to Choline and Acetate
  • decrease the amount of ACh that can be formed and released at synaptic membrane
  • increase and prolong the effect of released ACh
    Drug of choice for Myasthenia Gravis
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5
Q

Where and How does Hemicholinium act:

A
  • acts on the choline transporter
  • blocks reuptake of choline to decrease the synthesis of ACh
  • open channel block at all nicotinic receptors (can not be over come by an increase in ACh)
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6
Q

Where and How does Vesamicol act:

A
  • blocks Choline Acetyltransferase

- prevents the creation and transportation of ACh into the vesicles

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7
Q

Where and How does Botulinum act:

A
  • blocks vesicular release of ACh at the NMJ by cleaving docking proteins
  • results in weakening to flaccid paralysis of skeletal muscles
  • reversal takes up to 3-4 months
  • Botulinum neurotoxin A (Botox) - cleaves SNAP 25
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8
Q

Where and How does 4-aminopyridine (4-AP) act:

A
  • enhances the release of ACh at the synaptic cleft
  • prolonges the action potential by blocking potassium channels
  • allows for conduction through nerves damaged by loss of myelin
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9
Q

Therapeutic uses of 4-aminopyridine:

A
  • Multiple Sclerosis
  • Myasthenia Gravis
  • Spinal Cord injury
    Not used for these because of narrow therapeutic index and propensity of the drug to cause tremors and induce seizure
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10
Q

Multiple Sclerosis

A
  • an autoimmine disease characterized by intermittent demyelination of nerve fibers in the brain
  • results in progressive loss of motor coordination and muscle strength
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11
Q

Therapeutic uses of Botulinum Neurotoxin A

A
  • Cosmestic
  • Opthalmic
  • Face and Neck Muscle Spasms
  • Hyperdrosis
  • Pain
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12
Q

Use of Botulinum Neurotoxin A in Cosmetics

A
  • treatment of wrinkles
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13
Q

Opthalmic use of Botulinum Neurotoxin A

A
  • treatment of strabismus (imbalance of the eye muscle strength that impairs ability to focus both eyes on the same target)
  • treatment of bblepharospasm (spasmodic wrinking due to involuntary contraction of the eye lid muscle)
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14
Q

Use of Botulinum Neurotoxin A for Face and Neck Muscle Spasms

A
  • hemifacial spasm (one sided spasm of the facial muscles)

- cervical dystonia (abnormal tonicity in the muscles)

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15
Q

Use of Botulinum Neurotoxin A for Hyperhidrosis

A
  • excessive sweating on the palms, soles of the feet, axillae and face
  • very long action on sweat glands (4-12 months)
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16
Q

Use of Botulinum Neurotoxin A for Pain

A
  • may be effective to decrease severity and number of episodes of migraine headaches, lower back pain, myofasical (tigger point) pain
17
Q

Contraindications/side effects of Botulinum Toxin

A
  • should not be used in patients with neuromuscular disorders
  • most common problem is unintended local weakness muscles near the site of injection for blepharopasm and hemifacial spasm
  • eg ptosis most common problem
  • transient flu-like symptoms, anaphylaxis, and excessive fatigue
  • long term use can alter muscle fiber size
18
Q

Tubocurarine Side effects

A
  • hypotension caused by histamine release
  • increased salivation
  • autonomic ganglionic blockade
19
Q

Non-depolarizing NM blockers

A
  • Tubocurarine
  • Vecuronium
  • Atacurium
  • alpha-Bugartoxin (cobra venom)
20
Q

Atacurium Side Effects

A
  • slight histaime release causes hypotension
21
Q

alpha-Bungarotoxin Side effects

A
  • rapid paralysis of skeletal muscles including diaphragm
  • cuases death form respiratory failure
  • used for diagnostic purposes
22
Q

Depolarizing NM blockes

A
  • Succinylcholine
23
Q

Succinylcholine Side effects

A
  • Arrhythmias (bradycaardia and hyperkalemia)
  • emesis (vomiting)
  • muscular pain
  • increased intraocular pressure
24
Q

Order of paralysis of non-depolarizing neuromuscular blockers

A

eyelid -> tongue -> pharynx -> jaw muscles -> diaphragm -> limbs -> trunk -> musculature

25
Q

Mechanism of action of depolarizing neuromuscular blockers

A

binds to and activates receptor -> depolarization -> fasiculating muscles contraction -> maintained depolarization -> muscle relaxation -> desensitization of nicotinic receptor (channel block)

26
Q

Therapeutic uses of Non-depolarizing and depolarizing NM blockers

A
  • Surgical muscle relaxation
  • electroconvulsive therapy
  • mechanical respiration
27
Q

Use of Non-depolarizing and depolarizing NM blockers in surgical muscle relaxation

A
  • permits adequate skeletal muscle relaxation during general anesthesia
28
Q

Use of Non-depolarizing and depolarizing NM blockers in electroconvulsive therapy

A
  • usd to treat severe depression

- reduces or prevents muscle contration

29
Q

Use of Non-depolarizing and depolarizing NM blockers in mechanical respiration

A
  • prevents respiratory effort in patients receiving mechanical ventilation
30
Q

Mechanism of action of Dantrolene

A
  • reduces the release of calcium from the sacroplasmic reticulum
  • muscle relaxation is due to the decreased calcium
  • causes generalized mild muscle weakness and transient drowsiness
31
Q

Therapeutic use of Dantrolene

A
  • malignant hyperthermia

- spasticity

32
Q

Use of Dantrolene for malignant hyperthermia

A
  • effect of general anesthetic combined with muscle relaxants
  • results in a large increase in body temperature - if untreated would cause convulsions and even death
33
Q

Causes of Spasticity

A
  • spinal cord injury, stoke, MS, cerebral palsy etc..

PHAR 341 - Pharmacology (7 decks)

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