Skeletal Muscle: NMJ

Question 1

What is muscle tissue derived from?

Answer 1

Embryonic mesodermal germ cells

Question 2

What are the collective tissue components of muscles?

Answer 2

Epimysium - Surrounds entire muscle

Perimysium - Surrounds bundles of muscle fibers

Endomysium - Surrounds individual muscle fibers

Basement Membrane - Below endomysium

Question 3

What are satellite cells?

Answer 3

• Play a role in muscle growth/repair
• Increase # nuclei in mature fibers
• strength training

Question 4

What is the motor end plate?

Answer 4

Pocket formed around motor neuron by sarcolemma

Question 5

Describe the events which occur which lead to an action potential at the NMJ.

Answer 5

1. Neuron AP
2. Ca Entry
3. Ach release
4. Na entry via Nicotinic receptors
5. EPP local Na current brings Vm to threshold
6. Muscle fiber AP Na entry cia Voltage ganged channels
7. AP propagation
8. Ach degradation

Question 6

What are the two types of Nicotinic receptors?

Answer 6

Nicotinic Muscle - NMJ

Nicotinic NEuronal - Autonomic Ganglia

Question 7

What is a quanta?

Answer 7

Release of individual synaptic vesicle

Question 8

Describe pathology of myasthenia gravis.

Answer 8

• Autoimmune disorder wher Abs block Ach receptors at NMJ
• Decreases # receptors by 80%
• 10% have Ab against other plasma proteins NOT Cholinesterase

Question 9

What is Lambert-Eaton Syndrome?

Answer 9

• Ab saga isn’t Ca channels of NEuron of NMJ and there’re no transmitter release
• Commonly leads to small cell lung Carcinoma

Question 10

How is Lambert-Easton diagnosed?

Answer 10

• Uses EMG
• Repetitive stimulation of nerve muscle leads to progressive increase in contraction as Ca builds up in nerve terminal, while MG has a decrease in contraction strength

Question 11

What are Ach-esterase agonists?

Answer 11

Carbachol and suxamethonium

Question 12

What are Ach-esterase antagonists?

Answer 12

• Tubocurarine
• a-bungarotoxin
• a-conotoxin
• pancuronium

Question 13

What is Strychnos Toxifera?

Answer 13

Plant poison contains alkaloid tubocurarine which blocks Nicotinic receptors

Question 14

What is physostigmine?

Answer 14

• Reversible cholinesterase inhbiitor
• Obtained from calabar bean
• treats glaucoma and delayed gastric emptying

Question 15

What are symptoms f Ach overdose?

Answer 15

Abdominal cramps, Diarrhea, salivation, pinpoint pupils, and respiratory difficulty

Question 16

What are common effects and mechanisms of insecticides and chemical warfare agents? Treatment?

Answer 16

Acetylcholinesterase inhibitors

• Muscle twitches, Convulsions, pinpoint pupils, respiratory arrest
• Treat wth atropine

Question 17

Describe the action of pyridostigmine. Compared to other similar drugs?

Answer 17

• Inhibits muscarinic action of acetylcholine on structures innervated by postganglionic cholinergic nerves but not Nicotinic receptors
• Longer half life than others
• Fewer cholinergic side effects
• Does not crocs BBB

Question 18

What is the actions of tetrodotoxin?

Answer 18

Na Channel Inhibitor

Question 19

What is the action of Botulinum and tetanus?

Answer 19

Inhibit synaptic release

Question 20

What is the effect of curare

Answer 20

Inhibits receptors

Question 21

What is the effect of lead poisoning?

Answer 21

Calcium mediated toxicity

Question 22

What are three common sources of endogenous neurotoxins?

Answer 22

NO. Glutamate, and dopamine

Question 23

How does the action nod different Botulinum Toxins differ?

Answer 23

A/E - Cleave SNAP-25

B,D,F,G - Cleaves synaptobrevin

C1 - SNAP-25/syntaxin