Somatic NS

Question 1

characteristics of somatic ns

Answer 1

1. efferent (motor) + afferent (sensory)
2. ACh - NT
3. all ganglia in spinal cord
4. targets = nicotinic r on sk
5. excitatory effect

Question 2

drugs that block neuromuscular response

Answer 2

1. depolarizing agents
2. competitive antagonists
3. noncompetitive antagonist

Question 3

uses of neuromuscular blockers

Answer 3

1. muscle relaxants - surgical procedures / respirator / strabismus
2. treat muscle spasms
3. migraines + cosmetic surgery

Question 4

depolarizing agents

Answer 4

1. bind to ach receptor = produce prolonged action potential = hydrolyzed by BuChE
2. rapid onset/short duration
3. SUCCINYLCHOLINE CHLORIDE
4. surgical - muscle relaxant
5. SE:
   - electrolyte imbalance
   - bradycardia, cardiac arrhythmia
   - malignant hyperthermia

Question 5

succinylcholine apnea

Answer 5

1. recessive mutation in BUChE -> hypofunctional allele
   = paralysis
   - used with GE - check for muscle function

Question 6

malignant hyperthermia

Answer 6

mutation in SR Ca channel protein => excessive Ca release
=muscle spasm + elevated body temp
lethal
treat with SR Ca channel blockers

Question 7

competitive (non-depolarising) antagonists of Ach

Answer 7

1. bind to ach r in motor end plate = bind blocking of ach
2. slow onset/long duration
3. ATRACURIM
4. surgical - muscle relaxant
5. // hypotension - histamine release

Question 8

how do responses of DA/NDA agents differ

Answer 8

DA: phase 1+2

1: prolonged opening of nicotinic r channel = twitches
2. muscle paralysis

NDA: phase 2 only
- duration of opening of channels unaffected

Question 9

DA mechanism

Answer 9

DA = longer duration of action than ach = higher affinity for receptor + resistance to degradation by AChE

sk remains depolarised with high level of Ca in cytoplasm

pumped back eventually into SR - muscle relaxes but DA remains bound to receptor preventing binding of ach = contractions => paralysis

receptors become desensitized to ach during phase 2 = fail to respond to binding even if not bound to DA

Question 10

AChE inhibitor with DA vs NDA

Answer 10

DA = block of sk reversed enhanced

NDA = block of sk contraction reversed

Question 11

noncompetitive ACh antagonists

Answer 11

BOTOX - inhibits ACh release from pre neuron

• strabismus
• urinary incontinence
• migraine/headache
• cosmetic surgery

highly toxic if ingested

Question 12

myasthenia gravis

Answer 12

autoimmune disease - antibodies against ACh r

• muscle weakness
• fatigue

EDROPHONIUM - competitive AChE inhibitor = temporarily restores muscle function

PYRIDOSTIGMINE - AChE substrate inhibitor