11.26.13 Skeletal Muscle Paralytics

Question 1

Normal Skeletal Muscle Contraction

Answer 1

Somatic nerves releasing Acetylcholine
Acetylcholine interacting with nicotinic receptors to depolarize skeletal muscle
Release of calcium to contract skeletal muscle

Question 2

Somatic Nerves

Autonomic nerves

Answer 2

emanate from the spinal cord and innervate skeletal muscle with no synapses outside the CNS, Release acetylcholine (Ach), Ach interacts with a nicotinic receptor

Signal is terminated by degradation of Acetylcholine
Acetylcholinesterases mediate this degradation
Anticholinesterases are useful in treating Myasthenia gravis

innervate various organs and have a synapse outside the CNS

Question 3

Neuromuscular nicotinic receptor

Answer 3

is an iontropic channel
activated by NICOTINE or acetylcholine
activation results in:
Na influx
Depolarization
muscle action potential
opening of voltage-sensitive Ca2+ channel
release of Ca2+ from sarcoplasmic reticulum
contraction

Question 4

Efferent neurons from spinal cord

Answer 4

Virtually always release acetylcholine (sympathetic, parasympathetic, somatic)
The acetylcholine virtually always interacts with a nicotinic receptor (postganglionic nerve, adrenal medulla, skeletal muscle)

Question 5

For Review: Nerve activation leads to:

Answer 5

Acetylcholine Release 
Nicotinic Receptor Activation 
Sodium influx
muscle endplate depolarization 
muscle action potential (you can measure this with an electrode) 
Calcium influx (via voltage activated calcium channels) 
Calcium release (from sarcoplasmic reticulum) 
Calcium interaction with troponin 
Myosin-actin interaction (Muscle contraction- you can measure this with a force transducer)

Question 6

Drugs: (Neostigmine, Pyridostigmine, Edrophonium)

Answer 6

Something that prolongs Acetylcholine actions, will augment muscle contraction- relevant to Myasthenia gravis

Question 7

(Botulinum toxin)

Answer 7

Something that blocks acetycholine release. ) will prevent both muscle depolarization & contraction- relevant to cosmetics, muscle spasms

Question 8

(d-tubocurarine, Mivacurium)

Answer 8

Something that blocks nicotinic recptors. will prevent both muscle depolarization & contraction- relevant to surgical paralysis

Question 9

(Dantrolene)

Answer 9

Something that blocks calcium-induced calcium release (Dantrolene) will block contraction but not depolarization- relevant to Malignant Hyperthermia

Question 10

Myasthenia Gravis & Anticholinesterases

Answer 10

Autoimmune disease resulting in destruction of nicotinic receptors on skeletal muscle
Treatment includes anticholinesterases (pyridostigmine, neostigmine)
Diagnosis can include the short acting anticholinesterase edrophonium