Somatic nervous system leftover materials

Somatic nervous system

What branch?

• Peripheral nervous system → Somatic branch

Controls what muscle?

• Skeletal

What receptors? Location?

• Nicotinic-II receptors

• Neuromuscular junction (NMJ)

What neurotransmitter?

• Acetylcholine (ACh)

How do skeletal muscles contract?

• ACh binds to nicotinic II receptors — Deplorization of muscle fibers — Causes skeletal muscle contraction

How do skeletal muscles stop contracting?

• Acetylcholinesterase enzyme breaks down ACh — stops contraction

Drugs that inhibit skeletal muscle contraction is called?

Skeletal muscle relaxants

What are the 2 categories of skeletal muscle relaxants?

• Centrally acting skeletal muscle relaxants

  • Block conduction within spinal cord and brain to inhibit muscle contraction

  • Doesn’t interfere with NII or muscle fibers

  • Clinical indications

    • Muscle spasms, muscle strain, spasticity (stiff)

• Peripherally acting skeletal muscle relaxants

  • PNS (at NMJ)

  • Bind to nicotinic II receptors at NMJ — block ACh — inhibit muscle contraction

  • Clinical indications

    • Short surgical procedure

    • Abdominal surgeries

    • Electroconvulsive therapy (ECT)

Side effects of centrally acting muscle relaxants?

• Drowsiness

• Dizziness

• Lethargy

• Ataxia (loss of coordination)

What are the 3 types of neuromuscular blockers? (Peripherally acting)

• Depolarizing blockers

• Non-depolarizing blockers

• Direct-acting blockers

Depolarizing & Non depolarizing = Only IV

1 drug for depolarizing neuromuscular blocker?

succinylcholine

• Short duration

How do depolarizing blockers work?

Step 1: Binds to NII and causes depolarization

Step 2: Keeps NII desensitized, prevent response to ACh stimulation

How do non-depolarizing blockers work?

• Bind to NII receptors but do not activate them

• Block ACh from binding, NO depolarization

  • Doesn’t stimualate receptors

Drugs

• Tubocurarine

• Metocurine

• Pipecuronium

How do direct acting blockers work?

• Act directly on muscle fibers (Actin & Myosin) from contracting

Drugs

• Dantrolene

Side effects / adverse effects of depolarizing and nondepolarizing blockers?

Side effects

• Hypotension

• Vasodilation

Adverse effects

• Arrhythmia (Irregular heart beat)

• Bronchospasms (Tightening airway)

• Respiratory arrest (Breathing stop)

• Maligannt hyperthermia (rare)

  • Caution those w/ neuromuscular disorder (weak muscles)