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AUTONOMIC PHARMACOLOGY & PHYSIOLOGY

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  Baroreceptor pathways


AUTONOMIC ANATOMY & PHARMACOLOGY: PERIPHERAL


from University of Queensland
Principles
  • Motor neurons leaving the CNS release acetylcholine (ACh)
    • Acts on nicotinic AChRs.
    • Somatic motor neuron synapses contain AChRs blocked by α-bungarotoxin & tubocurarine
    • Autonomic motor neuron (preganglionic) synapses (in ganglia) contain
      • Nicotinic AChRs: Blocked by hexamethonium, but not by α-bungarotoxin
      • Some muscarinic receptors: Blocked by atropine
      • Chromaffin cels in the adrenal medulla
        • Modified sympathetic ganglion cells
        • Contain only nicotinic receptors
  • Postganglionic parasympathetic terminals release ACh: Acts on muscarinic AChRs
  • Postganglionic sympathetic terminals
    • Usually release noradrenaline: Acts on α, β1, or β2 adrenoceptors
    • Eccrine sweat glands and pilierector muscles: ACh acts on muscarinic AChRs
  • Sympathetic system arises from thoracic & lumbar levels
  • Parasympathetic system arises from cranial & sacral levels


ORGAN-SPECIFIC EFFECTS OF AUTONOMIC ACTIVITY

General Principles
  • Parasympathetic & sympathetic systems often have antagonistic effects in each organ
  • Sweat glands and most vascular smooth muscles have only sympathetic innervation
  • Ciliary muscle of the eye has only parasympathetic innervation
  • Bronchial smooth muscle
    • Only parasympathetic innervation: Constriction
    • Smooth muscle sensitive to circulating adrenaline: Dilation
  • Salivary glands: Systems produce similar, rather than opposite, effects

OrganSympathetic StimulationParasympathetic Stimulation
Heart Rate (β1 & β2) Rate
Contractile force (β1 & β2) Contractile force
Conduction velocity Conduction velocity
Artery Constriction (α1) Dilation
Dilation (β2)
Vein Constriction (α1)  
Dilation (β2)
Lung Bronchial muscle:
Relaxation (β2)
Bronchial muscle contraction
Bronchial gland secretion
Gastrointestinal tract Motility (β2) Motility
Sphincter: Contraction (α) Sphincter: Relaxation
Liver Glycogenolysis (β2 & α) Glycogen synthesis
Gluconeogenesis (β2 & α)
Lipolysis (β2 & α)
Kidney Renin secretion (β2)  
Bladder Detrusor: Relaxation (β2) Detrusor: Contraction
Sphincter: Contraction (α) Sphincter: Relaxation
Uterus Contraction: Pregnant uterus (α)  
Relaxation: Pregnant &
non-pregnant uterus (β2)
Eye Pupil: Dilate (α) Pupil: Constrict
Lacrimal gland secretions
Salivary glands
 Submandibular
 Parotid
Viscous secretions (α) Watery secretions



BARORECEPTOR PATHWAYS: CENTRAL




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2/18/2002