Parasympathetic Nervous System Notes

Parasympathetic Nervous System Overview

  • The parasympathetic nervous system (PNS) is responsible for rest and digest functions.
  • Ganglia in the PNS contain postganglionic neurons that travel to target organs.

Preganglionic Neurons

  • Preganglionic neurons are located in the central nervous system (CNS).
  • Often associated with branches of the trigeminal nerve (V).
  • Trigeminal nerve has no sympathetic or parasympathetic functions directly.
  • Preganglionic fibers send signals to cranial nerves to reach parasympathetic ganglia.

Types of Parasympathetic Ganglia

Ciliary Ganglia
  • Location: In the orbit, lateral to the optic nerve.
  • Associated With: Oculomotor nerve (CN III) and nasociliary nerve (branch of V1).
  • Function:
    • Supplies:
    1. Ciliary muscle - controls lens curvature for focusing on near/far objects.
    2. Constrictor pupillae - regulates light entering the eye.
  • Preganglionic fibers originate from the Edinger-Westphal nucleus in the midbrain.
Pterygopalatine Ganglia
  • Associated With: Maxillary nerve (V2).
  • Function: Primarily supplies the lacrimal gland.
  • Preganglionic fibers travel from the facial nerve (CN VII) through the greater petrosal nerve and terminate in this ganglia.
  • Postganglionic fibers travel through the zygomatic nerve (from V2) to supply the lacrimal gland and create tears (lacrimation).
Submandibular Ganglia
  • Associated With: Lingual nerve (V3).
  • Supplies submandibular and sublingual salivary glands.
  • Preganglionic fibers from the superior salivatory nucleus (pons) pass through the facial nerve, geniculate ganglia, and then the chorda tympani to the submandibular ganglia.
  • Postganglionic fibers provide secretions to the glands.
Otic Ganglia
  • Location: Medial to the mandibular nerve (V3) after it passes through the foramen ovale.
  • Associated With: Glossopharyngeal nerve (CN IX).
  • Preganglionic fibers from the inferior salivatory nucleus enter the tympanic plexus.
  • Fibers go through the lesser petrosal nerve to reach the otic ganglia, which supply the parotid gland via the auriculotemporal nerve.

Summary of Ganglia Relationships

  1. Ciliary Ganglia - Associated with nasociliary nerve (branch of V1).
  2. Pterygopalatine Ganglia - Associated with maxillary nerve (V2).
  3. Submandibular Ganglia - Associated with lingual nerve (branch of V3).
  4. Otic Ganglia - Associated with V3 after passing through foramen ovale.

Clinical Significance

  • Crocodile Tears Syndrome: Damage to the facial nerve can cause a patient to tear instead of salivating upon seeing or smelling food. This occurs if regeneration leads fibers intended for the salivary glands to connect with the lacrimal gland, especially if the lesion is at or before the geniculate ganglia.