Learning Objective: At the end of this lesson, the learner should be able to describe the parasympathetic ganglia of the head and neck, their origins, pathways, and target organs, and correlate these pathways with relevant clinical conditions such as Adie’s pupil.

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The parasympathetic nervous system (PNS) is a division of the autonomic nervous system, acting involuntarily to maintain homeostasis in concert with the sympathetic system. Its actions are summarized as “rest and digest”, promoting glandular secretion, decreased heart rate, and smooth muscle relaxation in most organs.

Parasympathetic fibres supplying the head and neck originate from four nuclei within the brainstem, each associated with one of the following cranial nerves:

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Parasympathetic Ganglia of the Head

There are four key parasympathetic ganglia in the head. Each ganglion receives preganglionic fibres from a cranial nerve, synapses there, and sends postganglionic fibres to target structures.

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Ciliary Ganglion

Location: Within the bony orbit, between the lateral rectus muscle and the optic nerve.
Preganglionic fibres: From the Edinger–Westphal nucleus via the oculomotor nerve (CN III).
Postganglionic fibres: Travel through the short ciliary nerves to the eyeball.
Target organs:

• Sphincter pupillae → constricts pupil
• Ciliary muscle → lens accommodation for near vision

Passing fibres:

• Sympathetic (from internal carotid plexus) – to dilator pupillae
• Sensory (from nasociliary branch of CN V1) – to cornea and iris

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Pterygopalatine Ganglion

Location: Within the pterygopalatine fossa, posterior to the maxilla.
Preganglionic fibres: From the superior salivatory nucleus (CN VII) via the greater petrosal nerve → nerve of pterygoid canal.
Postganglionic fibres: Hitchhike on maxillary nerve (CN V2) branches.
Target organs:

• Lacrimal gland (tear secretion)
• Mucous glands of the nasal cavity, palate, and nasopharynx

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Submandibular Ganglion

Location: Suspended from the lingual nerve (branch of CN V3), below the oral cavity.
Preganglionic fibres: From superior salivatory nucleus via facial nerve (CN VII) → chorda tympani → lingual nerve.
Postganglionic fibres: Directly innervate:

• Submandibular gland
• Sublingual gland
  → Both for salivation.

Passing fibres: Sympathetic fibres from the facial artery plexus to the oral glands.

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Otic Ganglion

Location: Below the foramen ovale, in the infratemporal fossa, medial to CN V3.
Preganglionic fibres: From the inferior salivatory nucleus (CN IX) via the lesser petrosal nerve.
Postganglionic fibres: Hitchhike with auriculotemporal nerve (CN V3).
Target organ:

• Parotid gland – secretomotor control of saliva

Passing fibres: Sympathetic fibres from the superior cervical chain via the middle meningeal artery.

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Vagus Nerve (CN X)

Although not associated with a discrete ganglion in the head, the vagus nerve provides parasympathetic supply to thoracic and abdominal viscera, including:

• Smooth muscle of the trachea and bronchi
• Gastrointestinal tract to the proximal two-thirds of the transverse colon

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Clinical Correlation

Adie’s (Tonic) Pupil

Definition:
A neurological condition characterized by a unilaterally dilated pupil that reacts slowly (or not at all) to light but constricts with near vision (accommodation).

Cause:
Damage to the ciliary ganglion or postganglionic fibres of CN III often follows viral infection or inflammation.

Symptoms:

• One pupil is larger than the other (anisocoria)
• Poor light reaction
• Normal or exaggerated accommodation response

Mnemonic: Adie’s pupil = Affected pupil reacts when you “Add focus” (accommodation)

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Summary Table