Pharmacology - Organization of the Nervous System:

Central

  • Brain
    • Chemoreceptor Trigger Zone
      • Function: Nausea and emesis initiation
        • Pro-emetic receptors: 5HT3, acetylcholine, histamine, dopamine, and opioid

Peripheral

  • Somatic
    • Function: voluntary control of skeletal muscles
      • End-organ receptor: nicotinic acetylcholine
  • Autonomic (involuntary regulator of homeostasis)
    • Sympathetic
      • Origin: T1-L2
      • Function: ‘fight or flight’
      • End-organ receptors: adrenergic
    • Parasympathetic
      • Origin: Cranial nerves 3, 7, 9, 10 and S2-4
      • Function - ‘rest and digest’
      • End-organ receptor: muscarinic acetylcholine

Table 1: Major physiologic effects of the autonomic nervous system.

System

Sympathetic

Parasympathetic

Eye

Pupillary dilation (α1)

Pupillary constriction

Cardiovascular

Increased heart rate (β1)

Increased conduction (β1)

Increased contractility (β1)

Coronary vasodilatation (β1)

Vascular smooth muscle contraction (α1/α2) and relaxation (β2)

Decreased heart rate

Decreased conduction

Decreased contractility

Respiratory

Bronchial smooth muscle relaxation (β2)

Increased bronchial secretion (α1, β2)

Bronchial smooth muscle contraction

Increased bronchial secretion

Gastrointestinal

Decreased wall motility and tone (β2

Sphincter contraction (α2)

Increased salivary gland secretion (α1, β2)

Increased wall motility and tone

Sphincter relaxation

Increased salivary gland secretion

Genitourinary

Bladder wall relaxation (β2)

Sphincter contraction (α1)

Uterine relaxation (β2)

Uterine contraction (α)

Bladder wall contraction

Sphincter relaxation

Uterine contraction


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